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(Information now  available indicates that some species below  are fortunately widespread and may be more stable than previously thought.)

New,  re: species below, July 09, Pseudiron videos,  see Home, and also the last species discussion  on this page. 

New, August 09, Raptoheptagenia photos, see Lemsford Ferry.

Reports on individual species

The five species covered below  on this page are Ametropus neavei McDunnough, Analetris eximia Edmunds,  Lachlania saskatchewanensis Ide,  Macdunnoa nipawinia Lehmkuhl, and Pseudiron centralis McDunnough.

See also Additional species of interest : Covered   here are:

1. Anepeorus rusticus McDunnough

2. Raptoheptagenia cruentata Whiting and Lehmkuhl, 

See Home and Lemsford Ferry for photos of R. cruentata..

3. Acanthamola pubescens Whiting and Lehmkuhl

4. Choroterpes albiannulata McDunnough

5. Traverella albertana (McDunnough) (see video).

 The  species  are  discussed below:

  • Ametropus neavei, now disappearing,  is restricted to submerged sandbars
  • Analetris exemia is very rare and  fish-like swimmer and predator
  • Lachlania saskatchewanensis is rathr uncommon and of ecological interest, see video
  • Macdunnoa nipawinia is rarely collected
  • Pseudiron centralis has strict habitat requirements and is becoming rare, see video

 back to Ephemeroptera       Home

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   Ametropus neavei McDunnough  

Summary notes- becoming rare in the past few  years, formerly abundant, this is  a very unusual   mayfly - very few biologist have ever seen or collected members of this genus.  It lives on sandbars in rivers; known distribution is very limited.    It uses the four hind claws to grip into shifting sand, it faces upstream to filter out food particles from the passing current.  A search for this formerly locally abundant is a top priority for this page.

see also for Montana:
  Powder River,  MT: Custer Co., Powder River, 11-XI-1976, ...
www.famu.org/mayfly/pubs/pub_w/pubwaltzr1998p213.pdf

drawings  below by Shirley Shepstone in my lab. DL





 


                 Ametropus neavei McDunnough cont.

Adults- Three caudal filaments (tails); 13-15 mm body length; hind tarsi 4 segmented; claws dissimilar on all tarsi; fore wings with two pairs of cubital intercalaries, vein A1 attached to hind margin by a series of veinlets; hind wing with acute costal projection.
Nymphs- Easily identified from the illustration above; body of mature nymphs about 15 mm total length, flattened; three caudal filaments (tails); head nearly square from above; mouthparts directed downward; claws of middle and hind legs long and straight, as long as tarsi and about twice as long as tibiae; claws on front legs thin, with 4 or 5 long spines; with 7 pairs of large lateral gills.

Taxonomy and Distribution- A single species is found in Saskatchewan; future studies may conclude that the Saskatchewan species is the same as a Utah population, and not conspecific with the Alberta population, as reported by Allen and Edmunds (1976).   I have examined species of all populations, and that is my opinion.   In this case, the names will change as described above.

Habitat- Larvae are restricted to sand bars or current swept substrate in large, unpolluted rivers. Here it digs into and grips the sand with 4 long legs and tarsal claws, and it faces upstream and filters food from the passing current with fringes on the legs and mouthparts. 

Distribution and status- This species was llocally abundant in the Saskatchewan River system, but has been difficult to find in the past few years (2009 and prior)  Most of its range here has been eliminated, especially by dams and reservoirs (Diefenbaker Lake/Gardiner Dam, Tobin Lake, and Nipawin Dam),  and also  by organic pollution.  In terms of life cycle I  have found  that nymphs are present throughout most of the year, and adults emerge in June and July. Eggs apparently hatch immediately after oviposition by females.   

 Ametropus neavei McDunnough cont

Population Size and Trends - recently cannot be located, but I  found this species in very large numbers and at widespread locations over the past  years, beginning in 1970.    Sites range from Queen Elizabeth Power Station, Saskatoon, 27 July 2000 to Lemsford Ferry, South Saskatchewan River, 4 Septmeber 2000). Some sites and habitats (Borden Bridge, North Saskatchewan River, Cecil Ferry, North Saskatchewan River, appeared to be unpolluted and unaltered, and probably continue to support populations of this species, . Samples I took  in the summer of 2000 were taken at a time when the species was not abundant because of life cycle reasons, and it was usually present in densities of about 0.5 specimens per square meter. It was also absent from many samples of 30 meters kick/sweep sampling, so this figure does not have much meaning, except to indicate densities in most favourable habitats.

Limiting factors and threats- This species is especially vulnerable to organic  pollution, siltation, and contamination of the clean sand bars that it inhabits. It is less affected by thermal regime alteration than other species, since it does not depend on a period of freezing temperatures to stimulate egg hatching.  It has been eliminated downstream from Saskatoon  by sewage, and it is of course not present in the lakes created by dams on the river. 


Details of Saskatchewan Distribution (my records only)-I have made collections from the river at Saskatoon, Lemsford Ferry, Cecil Ferry near Prince Albert, the North Saskatchewan River at Hyws. 5 and 12, and from Maymont and Maidstone Ferries. All of these collections are prior to 1978. It is known that the species is absent from large stretches of the river, such as in Diefenbaker and the other lakes made by reservoirs, and from immediately downstream from Gardiner Dam, and from areas downstream from Saskatoon that are effected by sewage.

Habitat I have found (unpublished) that in the Saskatchewan River system, A. neavei was one of the dominant members of the benthic community in certain areas of the river in the 1970's. Since 1970, hundreds of nymphs and numerous adults were collected at various sites in the river. Nymphs inhabited the extensive submerged sandbars which are abundant in the Saskatchewan River. These sandbars were often covered by only one or two feet of water. By walking to these with waders and by backing against the current while sweeping a net through the disturbed sand, one could typically collect one or two nymphs per half/meter of upstream walking. During flood stage, nymphs were frequently collected with a net in muddy eddys along shore where they had been swept by the current. In the fall, small nymphs were often collected in slow, deep water on muddy substrate near shore, suggesting that eggs might be carried here by the current, and that this was the site of hatching.  This is speculation.  As the nymphs grew, they apparently migrated to the sand substrate and remained there except when they were dislodged by the current.

Live nymphs on a sand substrate  observed in the laboratory (Lehmkuhl unpublished)

Nymphs are capable of both vertical and horizontal "wagging" of the abdomen. They are excellent swimmers and rival small fish. When swimming, nymphs hold the legs posteriorly against the body and perform a rapid vertical flipping of the abdomen. The nymph then alights on the posterior four legs (which have long tarsal claws) and by a shivering motion of the body the long claws sink into the sand. The long claws pull toward a central point like 4 ice tongs, and the animal is able to establish an effective grip on the unstable substrate. 'The body is then drawn to the substrate and with a lateral and horizontal tail-waging motion the animal sinks into the sand, soon to be covered except the head. At the same time, the shorter front legs clear sand away from the front of the head with a "dog­paddling" or swimming like motion and soon all that is seen is the projecting eyes, upright antennae, and the active front legs. The body becomes buried in the sand, and a cavity is created by the front legs in front of the head. The hairs on the front legs and claws, the hairs on the coxal lobes, and the hairs on the sternal flap form a basket-like area which presumably filters particles of food from the current which is passing over the animal (Lehmkuhl, unpublished). If startled, the animal is capable of quick withdrawal and it disappears under the sand. In the laboratory, nymphs would greedily accept particles of dried fish food dropped into the cavity in the sand in front of the head. In an analysis of gut contents of freshly collected individuals, they were found to be stuffed with sand and unidentifiable plant fragments. No animal remains (insect exoskeletons or zooplankton) were found. The gills of nymphs were not seen to move individually. Nymphs in the laboratory often performed vertical undulations of the entire body, typical rates of undulation being once every two seconds, and this was interpreted as a respiratory movement.

Other Information Edmunds, Jenson, and Berner, 1976 report "The nymphs bury themselves in firm, slightly silty sand in large rivers with a relatively strong current. The sand must be firm, smooth, and clean; in most rivers the nymphs are found only in a very small percentage of the sandy bottom. In the Blacks Fork River from Granger, Wyoming, to Interstate 80, localities have been found with fifteen or more nymphs per square meter. Nymphs have been taken in New Mexico from a warm river at an altitude of 5,400 feet; they occur in similar rivers in Utah, Colorado, Wyoming, Montana, Oregon, Washington, Alberta, and Saskatchewan, although the northern records are from lower altitudes." 

Life cycle- (Lehmkuhl, unpublished) In Saskatchewan, small nymphs were collected in September and October, and mature nymphs were collected in April, May, June, and July. Adults were collected in June, July and August. Thus, in summary, after adults emerge and lay eggs in mid-summer, the eggs hatch almost immediately, and growth of nymphs takes almost one year.

Edmunds, Jensen, and Berner (1976) report a similar life cycle, and they say "Adults have been collected from May through July. A. albrighti requires almost one year for development, Young nymphs appear shortly after the adults emerge and become mature the next year. The nymphs are highly variable in size, indicating an emergence period of a month or more"


Special significance of the species-

This species generally can survive only in large rivers such as the Saskatchewan where conditions for current, substrate, and a food supply are met. It belongs to an extremely unusual family. No other mayflies are similar, except the 2 or 3 species known form this Genus. It is vulnerable to total elimination if river habitats are destroyed. Already,  75 %  or more of its habitat has been destroyed in the Saskatachewan River, mostly by dams which form lakes, and also from sewage pollution and subsequent alteration of the river substrate. 

Population numbers, sizes, and trends

In the summer of 2000, the species was collected from Saskatoon at the Queen Elizabeth Power Station (27 July 2000) on the west side of the river, on sand bars. The species was absent from this site on 29 June 2000, even though collection conditions were good, and the habitat looked favorable (no signs of pollution or alteration). The absence is probably explained by the life cycle. The end of adult emergence is know to be in July and August, and the first newly hatched nymphs have been found in September in the past. Thus, the 29 June collection date may have been too late to collect last year's nymphs, and too early to collect the new generation of nymphs.

On 27 July 2000 at Queen Elizabeth Power station, three nymphs were collected in a single 20 meter kick/sweep sample over sand bars ( a total of 3 nymphs, thus, an estimated 0.5 nymphs/sq. meter on this sample), but none were collected in subsequent sampling of 300 meters of kick/sweep samples over sand bars at this location.

Small larvae (nymphs) were collected at Lemsford Ferry on 4 September 2000 at densities similar to that at QEP Station.

None were collected from other sites sampled in the river system (Borden Bridge, St. Louis, Cecil Ferry, Clarksboro Ferny) but this was probably because of the life cycle. Sampling dates in these areas were June and July, and as was the case at QEP Station in Saskatoon in June, nymphs may have been absent for the reasons given above. It would appear from the survey of 2000 that the species was well established and widespread in the system at the time, since collections (though small in number of specimens) were made in widely distributed regions of the river. Some sites and habitats, though not yielding specimens, appeared to be unpolluted and unaltered, and probably support populations of this species. 

Limiting Factors- This species has been effected by construction of dams, because the species cannot exist in the lakes formed by dams. It has also been effected by substrate alteration caused by sewage pollution, e.g. near Saskatoon. Downstream from dams, thermal regime alteration is a less serious factor for this species than others (Lehmkuhl, 1972) because eggs do not depend on exposure to cold temperatures to stimulate hatching. Eggs appear to hatch in the fall, soon after being laid by adults in mid-summer (field observations; no laboratory studies have been done). 

      *******************************************************************

Family Acanthametropodidae

Genus Analetris

Analetris eximia Edmunds 1972

Edmunds, Jensen, and Berner (1976) say of the Subfamily" it is one of the least known subfamilies and it is extremely rare in collections." Edmunds and Koss (1972) say: "The subfamily Acanthametropodinae is one of the least known mayfly groups and a reasonable understanding of the taxon is available now for the first time---"
They then describe the Genus and species, from specimens from Wyoming, Utah, and Saskatchewan.


Analetris.pdf

See also:  (Citation for data on this website:
"A Sand-dwelling Mayfly — Analetris eximia.  Montana Field Guide.  Retrieved on April 30, 2009, from http://FieldGuide.mt.gov/detail_IIEPH76010.aspx)"


Description

Adults- Eyes of male nearly touching from above; hind wing without a costal projection, hind wing large, about half the length of the front wing; the three caudal filaments (tails) about equal in length. Tarsal claws dissimilar.

Nymphs- Easily identified by comparing with the figure above, plus: body length of mature specimens about 15 mm, pale coloration (much lighter than the impression given by th figure above, oval gills present on segments 1-7, gills with two small ventral flaps, three caudal filaments, claws long and thin, longer than tarsi.

Distribution- Saskatchewan: North and South Saskatchewan River.
U. S.: formerly known from Utah, now eliminated by flooding from
reservoirs, also from the Green River at Buckboard Flats, Sweetwater Co.,
Wyoming (Edmunds and Koss, 1972) .

Habitat- In Saskatchewan, I collected nymphs in slow moving eddies and backwaters sheltered from the main current (e.g. by ferry ramps), or among boulders artificially placed along the river bank to prevent erosion. The preferred habitat is not known, and the species is extremely difficult to collect under most circumstances. However, after the normal July floods, it can often be collected in large numbers in backwaters, presumably displaced to these areas by the flood from the normal habitat. They are extremely vigorous swimmers and usually evade collecting nets.

Biology- This species is an aggressive predator, which is very unusual in the Mayflies. The genus, and the entire family, is considered extremely rare. It has already been eliminated from large areas in the U. S. by dams and pollution. It was locally abundant in Saskatchewan, but recent status is not known. Small nymphs have been collected in June in Saskatchewan, and adults have been collected in July. It is assumed that most of the year is passed as a diapausing egg. Therefore, the species would depend on a normal thermal regime to stimulate egg hatching.

Population size and trends-

In the summer of 2000 (2 July), this speces was collected at Borden Bridge, North Saskatchewan River at Hwy. 5. This species is notorious for being difficult to collect, because of it has vigorous, fish-like, swimming abilities. I regard this collection of a single nymph, in combination with field observations on habitat, as being very significant, and as evidence that the species has healthy populations in the river system at least until recently.

Formerly, the species was probably present throughout the Saskatchewan River system, but now has been eliminated in large sections of the Saskatchewan river by dams, reservoirs, sewage, and other pollution. It cannot live in lake conditions formed by major dams, for example. Populations were high in unaltered areas of the river in the late 1970' s. In the U. S., habitats are submerged by the Flaming Gorge Reservoir, and in the he Blacks Fork River, the species habitat is subject to multiple threats, including agriculture and domestic wastes, and spillage from oil drilling (Edmunds and Musser, 1960).  More than half, and perhaps as much as 3/4 of its habitat in Saskatchewan has already been destroyed.

Analetris eximia Edmunds 1972  cont.


Distribution- The species is known from  the Saskatchewan River in the Province of Saskatchewan. It is (or was) known from Wyoming and Utah (Edmunds and Koss 1972). In the South Saskatchewan River I have found it to be  abundant at Lemsford Ferry near the Alberta border, but it has not been collected at Saskatoon or other points downstream (northeast) from Gardiner Dam. I also found it  present at a number of localities in the North Saskatchewan River (Lloydminster Ferry near Alberta border, Battleford, Borden Bridge at Hwy. 5, and Cecil Ferry about 10 miles east of Prince Albert) but was not found downstream from Tobin Lake, a mainstream impoundment about 100 miles east of Prince Albert. These collection records are nearly 20 years old (mostly by me). The species was collected in the summer of 2 000 in the North River at Borden Bridge, Hwy. 5.

Habitat and habits-

It is known that nymphs are carnivorous (Edmunds and Koss 1972). I also found (Lehmkuhl, 1976) nymphs to be carnivorous; chironomids were the main food item in field collected specimens. In the laboratory they easily ate several chironomids which in total length exceed the length of the predator. Gut contents of field collected nymphs contained numerous chironomid head capsules.
Edmunds, Jensen, and Berner (1976) say nymphs are found in moderate to large, warm rivers on sandy bottoms with some silt (e.g. the Green River in Utah and Wyoming). In

Saskatchewan, they were usually collected in backwaters, where they had been carried by flood stages of the river. The normal habitat is unknown, possibly deep water in mid river. This is speculation.
Biology- I (Lehmkuhl 1976) reported on the life cycle: eggs hatch in spring after presumably passing the winter in a diapause stage; nymphs develop in May, June, and July; adults emerge in late July. Thus, the requirements are similar to Ephoron and the species would be sensitive to reservoir construction and thermal regime alteration.

Edmunds, Jensen, and Berner (1976) say nymphs were present from June through September.

I report (Lehmkuhl 1976) " of approximately 25 collections totaling about 200 specimens, collection dates range from 2 June to 31 July. Young nymphs (5-10 mm in length) were taken on 2 June 71, 12 July 70, and 14 July 71, and it could be assumed that hatching took place at least a month prior to these dates. Adults or nymphs with black wing pads (17-20 mm) were taken on 18 July 73 and 31 July 74. Thus, there appears to be an extended period of hatching and extended period of emergence but the rate of development is rapid. All takes place in mid-summer, It is hypothesized that the balance of the year (September to April) is passed as a diapausing egg or embryo."

Special Significance of the species-

The species is rare and endangered because of habitat destruction, dams, agriculture pollution, in both the U.S. and Canada. It is presumably restricted to the conditions provided by large river, since it has never been collected from streams.
The Subfamily to which it belongs is one of the least known subfamilies in the world, and all members are extremely rare in collections. Edmunds and Koss (1972) say "in the Acanthametropodinae, then, there are about 55 known specimens of 4 genera, of which 7 are imagos and subimagos. Analetris is the best represented genus but its known habitats are endangered. More than 40 miles of the Green River where Analetris presumably occurred have already been submerged behind Flaming Gorge Dam. The failure to collect more specimens is a result of a habitat in which it is difficult to collect, the shy and extremely fast swimming behavior of the nymphs, and inadequate collecting techniques. "

The status of the species is further discussed by Edmunds and Koss (1972) "since1947 many hours were expended in an effort to collect additional specimens from the Green River and its larger tributaries. In 1962-63 the Green River was inundated with water stored behind Flaming Gorge Dam and hope for additional specimens dimmed. In 1968 the junior author was successful in locating a population in a stretch of the Blacks Fork River from near Granger, Wyoming, to the crossing of the Blacks Fork River at Interstate Highway 80, about 7 miles east of Little America. He was able to rear one subimago male which enabled us to recognize that Siphluriscus was an Acanthametropodinae. It is not known how many miles of the Blacks Fork River support Analetris, but it is relatively short because in many summers the river is almost dry before it reaches Flaming Gorge Reservoir. Most of the river is not readily accessible, but it is in increasing danger from oil well drilling, agricultural development, dam building and pollution. In fact, five additional collecting attempts have produced no more specimens. Lehmkuhl (1970) collected a series of nymphs of the same species in the South Saskatchewan River. This river is also in danger from pollution."

Population Numbers, Sizes, and Trends

In the summer of 2000 (2 July), I found a single larva of this species at Borden Bridge, North Saskatchewan River at Hwy. 5. This species is very difficult to collect, because of its fish-like habits, and it is therefore not usually collected by insect sampling techniques. This collection of a single nymph, in combination with field observations on habitat, can be regarded as being very significant, and as evidence that the species has healthy populations in the river system at the time of this writing.  No major new developments have taken place in the las known habitats of the species.

______________________________________________________________________________

Lachlania saskatchewanensis Ide 1941

Family Oligoneuridae, 

            Lachlania powelli Edmunds 1951 synonym

see Video on Lemsford Ferry page



 





See also: 
A Mayfly — Lachlania saskatchewanensis.  Montana Field Guide.  http://FieldGuide.mt.gov/detail_IIEPH66030.aspx

Descriptions

Adults- With a white "H" shaped marking on the dark brown thorax between the wings, and with the following combination of characters: front wings with reduced veination, 3 or 4 crossveins and a forked vein in mid-wing, 3 pairs of legs which are similar: reduced, atrophied, and twisted; 2 caudal filaments (Figure 28).

Nymphs- This species can be easily recognized by the "H" shaped marking between the wingpads (above), and by the following combination of characters: body somewhat flattened, dark brown in color, total length  8-10 mm, eyes dorsal, two cerci (tails),  dorsal lateral gills on abdominal segments 2-7, front legs with a double row of long setae forming a fringe on the inner side.

Distribution-   The understanding of the species Lachlania saskatchewanensis  has recently changed and it is now considered to be a synonym of L. powelli. Thus the   species is known from Northwest Mexico and the Northwest and Southwest United States. In Canada it is known from the Saskatchewan River, and it is restricted to areas not affected by dams, impoundments, and serious pollution (e.g. Lemsford Ferry, Cecil Ferry).  My records are mostly from Lemsford Ferry, South Saskatchewan River, near the Alberta border,  with the exception of two collections from Cecil Ferry. 

 Habitat-.  I have collected this species only in swift water, about 1 meter deep, on the river bottom, clinging to roots that had been exposed by the current  (roots presumably from willows which line the shore).  It was also found on twigs which were dislodged by the collecting net.

 Conservation Biology-.  This species has been locally abundant, but the range in the river is very restricted.  Nymphs were collected from July to September; adults emerge in August and September.  Immature stages were absent from collections from October to June; they are presumably in the diapausing  egg stage at this time.  Based on field records, the species cannot tolerate the conditions upstream and downstream from dams, nor the conditions caused by sewage pollution.

Population Size and Trends
    In Canada, it seems to be  restricted   to the Saskatchewan River System. Evidence indicates that the species was once found in most of the Saskatchewan River system (about 1300 km of river), but by the 1970’s, it was eliminated from  most of the South Saskatchewan River by Gardiner Dam and Saskatoon sewage, and after 1986 was eliminated from most of the Main Saskatchewan River by the dams that formed Codette Lake and Tobin Lake. It is rare in the North Saskatchwan River, but is probably widespread.
     In the 1970’s the known range was very restricted.  Most specimens were collected from Lemsford Ferry, South Saskatchewan River, and only two records are from Cecil Ferry, North Saskatchewan River.  The type locality, based on a singe adult, is a salt lake many miles east of Saskatoon.  This adult was presumably blown by the wind from the river to the salt lake, perhaps from the Saskatoon area (Ide 1941). 
In  recent field sampling, adults were seen in flight on September 4, 2000 at Lemsford Ferry , and   single adult was collected.  No nymphs were collected on this date, probably because all nymphs had already emerged, and only adults were present. 
The Lemsford Ferry site was also visited and the river was sampled on 30 June 2000.  On this date the river showed signs of organic pollution (strings of filamentous algae attached to objects, coats and crusts of algal material on rocks, blackened undersides of stones, indicating anoxic conditions, see Figures 24 and 25).  No larvae were collected on this date.  This may have been because of polluted conditions, or it may have been because that nymphs had not yet hatched, and the absence was because of the life cycle.  

 Limiting Factors and Threats-It is known that Diefenbaker Lake and Gardiner Dam have eliminated the species from most of its range in the South Saskatchewan River.    The species is absent downstream from Saskatoon because of historically severe sewage pollution.   The species may be present in many parts of the North Saskatchewan River.  In nature, the species appears to be limited by a requirement for specialized substrate, namely willow roots or similar plant material where it can cling  while filter feeding from the current. 

More on taxonomy and classification

Family Oligoneuridae,

Lachlania saskatchewanensis Ide 1941

            Lachlania powelli Edmunds 1951 synonymTaxonomy-    

            The taxonomy of this species is not problematic. The Saskatchewan species is very similar to the species described from Utah and has been found to be a synonym.  The Saskatchewan species was described first, and the name has priority.

Adults -Adults are easily recognized from  the Figure, showing the "H" shaped marking on the thorax, plus: front wings with reduced veination, 3 or 4 crossveins and a forked vein in mid-wing, 3 pair of  similar legs which are  reduced, atrophied, and twisted; 2 caudal filaments, body dark brown, about 8 mm body length.Nymphs (Larvae)- Compare with the Figure, showing the "H" shaped marking, plus: body somewhat flattened, dark brown in color, total length about 8-10 mm, eyes dorsal, 3 pairs of legs, each with a single claw, two cerci (tails), dorsal lateral gills on abdominal segments 2-7, front legs with a double row of long setae forming a fringe on the inner side.

Detailed Description-(from Ide, F. P. 1941)
Lachlanis saskatchewanensis n. sp.  (original description)
 Female imago  (in alcohol).  Length 7.5 mm., wings 10 mm., caudal filaments 5 mm.  Head pale brown above with darker infuscation about the ocelli and a dark brown band extending in a curve between the lateral ocelli. On the vertex another dark brown patch in the form of a V.  Antennae with dark brown ring on the second segment, and the flagellum dark brown.  Frons extended as a hood over the mouth parts.
Thorax.  Pronotum dark umber brown with narrow  pale median line, some pale colour on lateral flanges.  Mesonotum dark umber brown with pale areas across anterior border and at bases of wings.  In addition a roughly H shaped pale marking on dorsum as in figure, this pale area being continuous posteriorly with pale lines which run out on the border of a peculiar flange developed laterally on the mesonotum.  Metanotum piceous, somewhat paler than the mesonotum.
 Abdomen piceous, the overlapping of the segments appearing as darker brown transverse bands.  On the anterior segments, lateral paramedial darker brown strokes nearer the posterior than anterior margin of the segment.  In the posterior segments which are somewhat darker than the anterior, these dark brown strokes are replaced by pale dots.  There is a very faint indication on some segments of a median pale line.  Caudal filaments (2) dark brown basally, with a pale patch on the mediaI surface.  Distally the segments separated by pale rings with a gradual dilution of the intensity of the brown colour towards the tip.  Ventrally the abdomen is somewhat paler in colour than dorsally.  On the anterior segment there is a very distinct paramedial dark  brown  stroke posteriorly and a more extensive sinuate dark line anteriorly.  The venter of segment seven is produced posteriorly and has an excavated border.  On this segment are vestiges of the nymphal gills in the form of minute curved appendages.

Legs pale amber with brown infuscation on femora and with coxae dark brown.  All legs similar, twisted and atrophied distally and probably non-functional .

     Wings.  Venation as in figure. whitish with no evidence of the bluish reflection which is mentioned in the descriptions of other species in the dried condition.

    Holotype,  Stoney Lake, near Humbolt, Saskatchewan.  September 5, 1940, J. E. Moore and J. S. Thompson.  In the collection of the Royal Ontario Museum of Zoology, Toronto.

 Nymph- There are no detailed  descriptions of L. saskatchewanensis in the literature, and technically,  "the nymph of the Canadian species is still unknown" (Edmunds, Jensen, and Berner, 1976).  Our species can be identified from the video and Figure , plus the following description from Edmunds, Jensen, and Berner (1976) for the genus Lachlania.

"Nymphal Characteristics. Body length: 8-10 mm.  Body somewhat depressed.  Head more or less flattened; eyes dorsal; maxillae with tufts of gills at bases.  Claws short and stout.  Abdomen somewhat flattened with lateral margins prolonged  into rather coarse posterolateral projections.  Ventral  gills on abdominal segment 1 small; gills on segments 2-7 dorsal, platelike, small. Two caudal filaments with rather sparse fringe of setae on in;ner margin."

Distribution. Since L. saskatchewanensis has recently been synonymized with L. powelli (Mayfly Central, google for this site), the species is now considered to range from Saskatchewan to Mexico, but it may have been eliminated from most its range by river development.  In Canada, it is known only from the Saskatchewan River, and probably it was once found throughout the 1300 km of river in Saskatchewan.  It has been eliminated from about 99% of the former range in the South and Main Saskatchewan Rivers.  The species is now found in about 10 square km of prime habitat and about 250 km of marginal habitat. The type locality is a salt lake (see Habitat, below), probably because of a wind-blown adult, far from the larval habitat.  The species was abundant in the 1970’s at Lemsford Ferry, South Saskatchewan River (B, Figure 1), near the Alberta border, and there are  two records from Cecil Ferry, North Saskatchewan River, near Prince Albert (Fig. 1).  In the summer of 2000, the species was collected only at Lemsford Ferry.

Ide (1941) says the following: "The genus Lachlania is neotropical, with three species described as follows, L. lucida Etn. from Guatemala, L. abnormis Hag. from Cuba, and L. pallipes Etn. from Ecuador".   Ide (1941) then continues on to describe L.  saskatchewanensis.

Edmunds, Jensen, and Berner (1976) add (about the family) "Although predominantly pantropical, the Oligonuriinae extend north in the Old World to Central Europe, Afghanistan, and Japan and in the New World to Saskatchewan….Only two genera cross from the Neotropical region into North America". 

  Habitat.  

The occurrence on the surface of a saline lake near Humboldt, Saskatchewan, of the adult female which is the type specimen of this species is most certainly accidental, the specimen having apparently been carried there by air currents form the Saskatchewan River, approximately 100 km. to the west.  Larval stages are known only from flowing water, and in Saskatchewan, only from large rivers.Nymphal Habitat-

            In Saskatchewan (Lehmkuhl, unpublished) nymphs were first collected on July 12, 1970, in the South Saskatchewan river at Lemsford Ferry, near the Saskatchewan-Alberta border.  Nymphs were collected with a long handled net in water about 1 meter deep in a strong current.  The nymphs were found clinging to roots(presumably from willows which line the shore) and twigs which were dislodged by the net from the current-swept river bed.  Laboratory observations revealed that the substrate was gripped by  the posterior 2 pair of legs and feeding takes place by the nymph facing into the current while the front pair of legs with their fringes are held upward and to the side of the head.  The front legs are alternately and rapidly flicked to the mouthparts, and presumably food particles are extracted from the fringes (Lehmkuhl, unpublished).

Edmunds, Berner, and Jensen (1976) add about the closely related Utah species: "The nymphs are usually found clinging to small sticks lodged in interstices among rocks in rapids or clinging to the undersides of rocks. In sandy stretches of rivers with considerable current submerged twigs may be literally covered with nymphs.----When disturbed, the nymphs tip the caudal filaments up over the back. They are slow moving and cling to sticks and rocks with great tenacity."

Life cycle

In Saskatchewan at Lemsford Ferry (Lehmkuhl, unpublished), I collected adults in August and September.  Immature stages were absent from October to June; eggs apparently have a long resting stage.  In 1970, 1971, and 1972, nymphs were collected from July to September, and they may have been present in June also but the high water from the annual flood and the resulting dangerous collecting conditions prevented collecting at this time.  Most growth of nymphs took place in July and August, the time of highest water temperatures.  Ice broke up in mid April and water temperatures in May and June are at or near 19 C.  In July and August, water temperatures rose to about 25 C.  In mid-August, water began to cool gradually to freezing in early November (Lehmkuhl, unpublished).

Edmunds, Jensen, and Berner (1976) say the following about the closely related Utah species "There is a single generation per year in Utah with length of nymphal life being about three months. Emergence in Utah and New Mexico occurs in August and early September. The adult life is extremely short, perhaps not more than four or five hours”.

“Mating Flights. Mating flights of L. powelli take place in midmorning, starting as eairly as 7:45 A.M., and in L. dencyanna from 11:30 A.M. to 1:30 P.M. The flight is very rapid, a characteristic which is probably common to all the Oligoneuriinae but which is unlike that of any other mayflies. The subimaginal skin is shed from all parts of the body except from the wings while the insects are in flight. Mass mating flights occur only on certain days, but the controlling ecological factors are unknown." 

 Special Significance of the species

            The distribution of this group is Neotropical and Nearctic. In the Nearctic the species extends north into Utah, Wyoming, and Saskatchewan. Mayflies of this group have been called “among the most distinctive known” because of the unusual morphology (Edmunds, Jensen, and Berner 1976).  The Saskatchwan  species can be considered rare , but it is locally abundant.  The range of the species  is limited to small sections of the Saskatchewan River, and it has been eliminated from many parts of the river by reservoirs and organic pollution.  The species could easily become extinct.

Population Numbers, Sizes and Trends

            The original distribution in Saskatchewan was probably the entire Saskatchewan River System, about 1300 km.  By the mid 1980’s, the species had been eliminated from about 99% of the South and Main Saskatchewan Rivers, especially by large dams and the lakes they for, and also by Saskatoon sewage.  Recovery has not occurred in the area affected by Saskatoon sewage.  The species is probably found in most of the North Saskatchewan River, but collections indicate that it is rare in this area. 

            The known area of distribution for this species in Canada is about 20 river km, or less than 10 square km.  The speculated area of distribution (North Saskatchewan River) is about 500 river km, perhaps 150 square km.  There are no recent nor even past collections from the latter, with the exception of the Cecil Ferry specimens.

 In the 1970’s, there were large populations in the Lemsford Ferry area.  In the summer of 2000, the river at Lemsford Ferry showed many signs of pollution- filamentous algae in long streamers attached to fixed objects, growths on the surface of rocks, and blackening of the undersides of rocks, indicating anoxic conditions (Figures 24 and 25).  No larvae were collected on 30 June 2000.  It may have been too early in the season, and larvae had not yet hatched from eggs.  On Sept 4, 2000, no larvae were collected, but adults were observed flying, and a single adult was collected.   It is not possible to comment on population sizes and trends, except to verify the the species  is still present at Lemsford Ferry.

Limiting Factors-

            It appears that this species requires the specialized habitat provided by the river, including a proper substrate for attachment  of the larvae (e.g. willow roots) and  a food supply as carried by the turbid waters of the river.  It also requires the thermal regime provided by the river to break diapause of the eggs (no detailed studies have been done, but this is the conclusion based on examination of the life cyce, and comparison with altered temperature regimens, which appear to eliminate the species.

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Macdunnoa nipawinia Lehmkuhl)




 






Macdunnoa nipawinia Lehmkuhl


Macdunnoa original desc Lehmkuhl.pdf

See also:   Citation for data on this website:
"A Sand-dwelling Mayfly — Macdunnoa nipawinia.  Montana Field Guide.  Retrieved on April 30, 2009, from http://FieldGuide.mt.gov/detail_IIEPH30030.aspx

 Description

            (Mayfly {Ephemeroptera} nymphs can be separated from all other Insecta  by the presence of  single claws on each of the 3 pairs of  legs, by the presence of lateral gills on the abdomen, and by the presence of two or three cerci (tails)).

            Nymphs- A small (8-10 mm), blackish or very dark brown species, with three caudal filaments which are strikingly white in contrast to the body, with  5 visible rather than 7 pairs of lateral gills (the sixth is hidden, the 7th is absent).

 (Adult Mayflies {Ephemeroptera}  can be separated from all other Insect Orders by the presence of 6 legs, the presence of two or three long cerci (tails) and by large, triangular wings, usually with many crossveins).

            Adults- Adult males can be separated from all other Heptageniidae by (1) median titillators of male genitalia thick and abruptly narrowed at the apex, (2) apex of the penes expanded laterally, lacking spines, and (3) male eyes separated  by 5 times the width of the median ocellus.

Distribution-Current data indicate that this is a true endemic species, known only from the Saskatchewan River and Battle River in Saskatchewan.  Two other members of the genus are known from the U.S. (Flowers 1982).

Habitat-Moderate river current, on decaying branches, under bark, sometimes in gravel. Since collecting efforts often do not lead to success, even though the collecting  site seems suitable, it appears that the habitat requirements of this species are not well understood.

Conservation Biology-This is a rare endemic species; both the Genus and species were first described from the Saskatchewan River by me.  Later, related species were found in the S.E. U. S.  (Flowers 1982).   It is seldom collected, but at times, has been  locally abundant in the Saskatchewan River.  It apparently feeds on plant material and organic debris; it is thought that most of the year is passed in the egg stage; Saskatchewan collections indicate that nymphs hatch in the spring, and adults emerge in June and July.  This species  is very different from any other Heptageniid relatives in appearance and morphology.

Population Size and Trends-  This species has been collected  throughout the river system, except where  major dams and  sewage have eliminated the species.  It has been eliminated from about 90% of the South River and about 99% of the main River, but may be present throughout the North River.  It is always rare, with single individuals being collected after great effort.  Present populations are probably stabe.

A single specimen was collected in the summer of 2000 at Lemsford Ferry (30 June).  The difficulty in  collecting  this rare species was noted above, so this single specimen may be indicative of usual levels of population in the river;  there is no reason to believe that  populations do not still exist in  areas where the species was  collected in the 1970’s, since it does not appear that these areas have  been disturbed or altered in any significant way in recent years (personal observations, summer 2000).  The Nipawin area populations have been eliminated by dam construction and Codette Lake.

Limiting Factors and Threats-  This species is known only from the Battle and  Saskatchewan Rivers.   Conditions apparently required  by this species include factors  such as a thermal regime which will stimulate hatching of eggs (compare Figure 8), and  the wood/gravel habitat where the species has been collected appears to be unique to the river, possibly related to the type of decay that occurs on wood in the river.  The main threat to this species is habitat destruction.  The most serious and large scale type of habitat destruction that is has occurred in the past  has been dam construction.  The species would also be vulnerable organic and toxic pollution.


Macdunnoa nipawinia Lehmkuhl 1979

  Family Heptageniidae           

Taxonomy-

            There are no taxonomic problems with this species.  I described both the genus and species as new from Saskatchewan.  Later, Flowers (1982) described two more species, from Florida, and from the Ohio River, and he added many details to the description of the genus.

Diagnostic Characters

Adults- Adult males can be separated from all other Heptageniidae by (from Flowers, 1982) (1) median titillators of male genitalia thick and abruptly narrowed at the apex, (2) apex of the penes expanded laterally, lacking spines, and (3) male eyes separated  by 5 times the width of the median ocellus. 

Nymphs- This is a small (8 mm), blackish or very dark bown species, with three caudal filaments which are strikingly white in contrast to the body, with  5 visible rather than 7 pairs of lateral gills (the sixth is hidden),  and with a stout spine at mid-length on tarsal claws. 

 

Distribution– The genus was discovered and the first species described from Saskatchewan, and subsequently, two additional species were placed in the genus.

 In the past the species has been collected from the Saskatchewan River and the Battle River.   Lehmkuhl (1979) has records from the South and Main Saskatchewan Rivers at Nipawin (this area is now flooded by a dam),  Birch Hills Ferry (near G, Figure 1),  and  Lemsford Ferry (B, Fig. 1), and from the Battle River south of Lashburn, and from the North Saskaatchewan River north of Lloydminster.

 In the survey in  the summer of 2000, a single emerging adult and cast larval skin were collected on 30 June  2000, at Lemsford Ferry, South Saskatchewan River, south of Kindersly. Since the species is rare and seldom collected, this is regarded as a good sign, the collection of even a single specimen being significant.

 Nymphal Habitat-( From Lehmkuhl ,1979) . D.H. Smith and I have found the species most reliably by searching on submerged wood, and under loose bark on decaying tree limbs. I have collected specimens from uniform gravel substrate in a smooth but rapid area of current in the North Saskatchewan River north of Lloydminster. They are apparently typical herbivores.

Flowers (1982) says that the related species M. brunnea, in Florida: "Nymphs live in rotting leaves among rocks in deep areas where the current is swift.  When living nymphs are place in still water, the move their gills in a wave-like motin, beginning with the first pair."5. Conservation Biology-  Life cycle (From Lehmkuhl 1979): “emergence, based on observations made during numerous attempts to obtain material for rearing, is restricted to a short period  in late June  and early July.  Exact time apparently varies with weather conditions in a given year. Small nymphs have been collected in early June, indicating that nymphs hatch in late spring and that most of the year is passed in the egg stage”.
 

Flowers (1982) says of M. brunnea in Florida  that adults emerge from May to early June, and adults commonly came to lights.

Special significance of the species-  The species was named for the town of Nipawin, and because of dam construction and the formation of a lake, it is now  extinct in that area.  Perhaps the species still exists in the type locality, Birch Hill Ferry  since major changes have not occurred in  this area that might negatively effect the species. 

            Lehmkuhl (1979) wrote   "Over the past several years a small series of mayfly nymphs which do not belong to any described genus have been collected by the author and coworkers from the Saskatchewan River. Adult females have been reared from nymphs but unfortunately no males were obtained." Lehmkuhl (1979)   then described the new genus and species.

            Flowers (1982) added to our knowledge of the genus and described a new species of Macdunnoa.  He said "Over the last three decades an interesting but rare heptageniid mayfly  nymph has been collected sporadically in eastern North America from Florida to Canada. The nymph is easily  recognized by its dark body, pale caudal filaments and greatly reduced abdominal gills 6 and 7.  Lehmkuhl (1979) discovered a population of these nymphs in Saskatchewan and reared female  imagos. He established the genus Macdunnoa for these nymphs and female imagos.".

 Population Size, Numbers-

                The species was once found in the entire 1300 km of Saskatchewan River in Saskatchewan, plus the Battle river (based present widespread distribution).  It has now been eliminated from about 90% of the South Saskatchewan River by Gardiner Dam and more than 90% of the Main Saskatchewan River by Codette and Tobin Lakes that resulted from dams on this river.  It may be present in normal numbers in the North Saskatchewan River, since there have been few new developments here.  Under all circumstances, this species   is rare and difficult to collect, so that the collection  of  a single specimen on 30 June  2000 at Lemsford Ferry is regarded as significant, and probably an indicator that the population of this species is stble.  The specimen was collected as a result of 300 meters of kick sample collection, covering a variety of microhabitats.  Based on these facts, the density would be 1 specimen per 100 square meters.

Limiting Factors- This species is found only in the river and thus apparently requires the conditions found in the river.  Habitat destruction, especially by dam construction, and also organic and chemical pollution, would harm this species, especially organic pollution which would alter the substrate.9. Existing Protection-  No protection exists that takes into account the special needs of this 

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 Pseudiron centralis McDunnough (see videos, Home, Mayflies, Ephemeroptera)



 






Pseudiron centralis McDunnough

       This rare species, seemingly restricted to sand bars in large rivers, is known from scattered localities in central and southeastern North America, and west to Saskatchewan, Manitoba, Wyoming, and Utah.    It is locally abundant in the Saskatchewan River, having been eliminated from large areas by the construction of dams (Gardiner Dam, Codette Lake, and  Tobin Lake (e.g. see Lehmkuhl, 1972) and pollution such as the sewage from Saskatoon.

       Special Significance of the species. This species is a rare specialized predator; predatory food habits are unusual in mayflies; most are herbivores.  There is but one genus in the family, and the species is morphologically and behaviorally  unique, being adapted to living and hunting on submerged sand bars, using the long claws to move crab-like over the shifting substrate, and using  long sensory palps to locate prey which burrow in the sand..  It has been eliminated from much of its former range in both the U. S. and Canada, and existing populations are vulnerable because its required habitat is also rare.

     Edmunds, Jensen, Berner (1979) say that nymphs and adults are rare in most collections and are poorly known.  They wrote:    “relatively rare genus is restricted to North America and is known from scattered localities”. 

        Habitat- Again, in the Saskatchewan River  it is found on sand bars, and Edmunds, Jensen, and Berner (1976) report a similar habitat.  It can be collected by sweeping with a long handled net over current swept sand bars.  It is seldom found by  general collecting methods and thus is rare in collections, but it can be found by searching in the specialized habitat.

Descriptions 

Adults- The combination of size (body length 12 mm), plus wing veination which is typical for the Heptageniidae, (i.e.-four intercalary veins), but with hind tarsus having four clearly differentiated segments, plus two cerci (two tails), separates this species from all others.  (Mayfly adults can be separated from all other Insect Orders by the presence of 3 pairs of legs, the presence of two or three cerci (tails), and by the large, triangular wings, usually with many crossveins).      

Nymphs- Recognized by the the long legs, the tarsal claws which are about as long as the tarsi, the flattened body, the elongate, slender, lateral gills with the small fibrillar tuft near the base, and the flagellum-like appendage on the ventral side on the posterior margin near the center of the gill. (Mayfly {Ephemeroptera} nymphs can be separated from all other Insect Orders by the presence of 6 legs, single claws on each leg, the presence of lateral gills on the abdomen, and the presence of two or three cerci {tails}).

      Discussion and Observations:   On submerged sandbars (photo), larvae can move backward, forward, and sideways by digging the long claws into the sand and moving crab-like over the substrate. It uses its palps to detect prey as it moves over the sandbars   (Lehmkuhl, personal observations of living specimens).ed      The original range in Saskatchewan was probably about 1300 km of river, but it has been entirely eliminated from much of its original habitat by dams.  It previously (based on my collections )  had high populations in small portions  of the North and South Saskatchewan Rivers.   Based on surveys by the author in the summer of 2000, the river populations appeared to be stable.  On June 29, 2000, it was abundant  (21 specimens in 30 meters of kick sample sweeping) at Queen Elizabeth Power Station, Saskatoon.  Two specimens were collected downstream at Clarksboro Ferry on 3 July 2000 from 300 meters of kick sampling  (i.e. about two specimens per 100 square meters), and a single specimen was collected at St. Louis on  8 July 2000 from 300 meters of kick sampling.  New-only three  immature (quarter to half mature size) specimens were collected at Queen Elizabeth Power Station on 4 July 2009.

        Life cycle- (from Lehmkuhl Unpublished) Nymphs ranging from 7-12 mm were collected on 29 June 1970. A l5 mm nymph was collected on l5 July l970.  Nymphs ranged from  8-18 mm on 13 July 1971, the largest having black wing pads.  Adults were collected on 15 July 1971.  Nymphs ranged in size from 12-17 mm (black wing pads) on 28 July 71. All of the above were from Saskatoon an  area with a temperature regime influenced by Gardiner Dam, which slightly lowers water temperature at this point (Lehmkuhl, 1972; see Figure 7).   A 5 mm nymph was collected at Lemsford Ferry on 2 June 71.  In summary, at Saskatoon, nymphs hatch in May, growth is rapid, and adults emerge in June and July.  New- the nymphs collected on July 4 2009 were small, about 1/3 mature size and smaller.  They seem small for this date compared to the records above.  Again, the collecting site is in the area cooled by Gardiner Dam.

        Classification and Relationships-

Class Insecta
Order Ephemeroptea (Mayflies)

Family Pseudironidae
      Pseudiron centralis McDunnough
                Pseudiron meridionalis Traver 1935, synonym

Taxonomy-
        Taxonomy is not a problem.  In the larval stage this is a morphologically and behaviorally unique mayfly which cannot be confused with any other.  A southeastern U. S. species has now been synonymized with the Saskatchewan species (http://entom.purdue.edu/entomology/research/mayfly/species.html, Mayfly Central, Purdue University).

Many more Technical details, for the record: under construction, editing in progress.

-
Adults- Wing veination typical for the Heptageniidae, i.e.-four intercalary veins; hind tarsus with four clearly differentiated segments, median caudal filament vestigal (i.e., two tails).

Nymphs- Easily recognized by comparing with Figure above, and by the somewhat flattened body, the tarsal claws which are as long as the tarsi, and the lateral gills which are elongate, slender, and with a small fibrillar tuft near the base on the ventral side; on the posterior margin near the center of the gill there is a flagellum-like appendage.

Detailed Description-Adults- (From Burks 1953), Genus level.
Pseudiron McDunnough (1931b:91). "The adult wing venation  is  typical  for  the Heptageniidae,  resembling  most  closely  that  of Rhithrogena,  but the hind tarsus has only  four clearly  differentiated  segments. The abdomen is quite long and slender, and the ninth sternite of the female has a median indentation on the posterior margin. The median caudal filament is vestigial in the adults of Pseudiron.

Species level (From Burks 1953)
Pseudiron centralis McDunnough  (1931b:91). MALE.-Length of body and of fore wing 12 mm. Head light yellow, with red-brown shading on face and on vertex between compound eyes; each antennal scape and pedicel red-tan, flagellum light yellow; compound eyes of living insect dark gray. Dorsum of thorax reddish brown, with narrow, yellow stripes on lateral sutures of mesonotum; pleura and sternum yellow. Legs markedly long and slender, yellow-brown, with a dark, red-brown crossband present at middle and at apex of each femur, each tibia and tarsal segment darkened at apex; wings hyaline, each brown stained in stigmatic area, veins and crossveins brown. Abdomen with broad dorsomedian, longitudinal,  brown  stripe, edges of this stripe extended to lateral margin at posterior margin of each tergite; abdominal sternum yellow, with ganglionic areas faintly brown-stained; genitalia, yelIow-brown; caudal filaments yellow, with basal two or three segments shaded with brown, articulations light brown, becoming colorless toward the apexes of the filaments. Females-Length of body 12-13 mm., of fore wing 13-14 mm.  Coloration almost identical with that of male except that dorsum of thorax is mostly yellow-brown; stigmatic area of fore wing not brown stained, veins and crossveins of hind wing almost or quite hyaline; ninth abdominal sternite incised on meson of posterior margin, fig. 307; caudal filaments white, basal articulations light brown.

Nymphs- From Burks 1953, Genus level

Pseudiron McDunnough (1931b:91).
Nymphs have a somewhat flattened, heptageniid-like head, with the eyes dorsal in position; in addition, the head is slightly elevated on the meson between the antennal bases, faintly suggesting the baetine head form. The mouth-parts evidently are fitted for predation (Spieth 1938a:3). The tarsal claws are longer than the tibiae.  The gills are elongate and slender, with a small fibrillar tuft near the base on the ventral side and a narrow, flagellum-like appendage near the center of the posterior margin, also on the ventral side of the gill.  This type of gill occurs in no other known member of the order Ephemeroptera.

From Burks, 1953, Pseudiron centralis, species level:

Nymph.-Length of body  12-13 mm. Head broad, flattened dorsally, but slightly elevated on median area between antennal bases--, Pronotum with lateral margins expanded laterally as thin, platelike projections--, Legs long, slender--, with each tarsal claw longer than respective tibia; wingpads showing venational pattern typical for this genus.  Abdomen long, slender, with lateral margins flaring; platelike, posterolateral angles acute on segments 8 and 9, rounded on more anterior segments, gills-- with a small fibrillar tuft near base and a flagellum-like projection near middle of posterior margin; apex of gill lanceolate; cerci each with a fringe of long setae on inner side only, median caudal filament bearing long setae on both sides.

 Distribution-Since the Saskatchewan species is now considered to be a synonym of the southeast U.S. species, the interpretation of the status of this species has changed  (Mayfly Central, see References).  Now, the species is known form northeast and northwest Canada, the northeast, northwest, southwest, and southeast United States, according to the distribution scheme used by Mayfly Central (Google this website or see references).

 In Saskatchewan, the original distribution was presumably most or all of the approximately 1300 km of the North, South, and Main Saskatchewan Rivers in Saskatchewan.

In Saskatchewan in the 1970’s, based on my samples, the species had been eliminated from about 90% of the South Saskatchewan River, and about 50 % of the main Saskatchewan River. It may have been present in most of the North Saskatchewan River.  My collections from the 1970’s are from Cecil Ferry, North Saskatchewan River, Clarksboro Ferry, South Saskatchewan River, Borden Bridge, North Saskatchewan River, Queen Elizibeth Power Station, Saskatoon, South Saskatachewan River (Lehmkuhl, unpublished).

 Other North American records include Wyoming, Manitoba, Utah, Illinois, Indiana, Iowa, Kansas, and Missouri (various sources, e.g. Burks 1953).  The current status is unknown in the U.S.

  In Saskatchewan, recent changes are that more habitat has been destroyed since 1986 by Codette Lake at Nipawin.    


    Population Numbers, Sizes, and Trends.     Populations in Saskatchewan are probably stable at this time, since there have been no major new developments on the river in the last decade.  The observed signs of organic water pollution at Lemsford Ferry, near the Albert border, may indicate future negative impacts.    My surveys in the summer of 2000 gave the following results:  June 29, 2000, abundant  (21 specimens in 30 meters of kick sample sweeping) at Queen Elizabeth Power Station, Saskatoon; uncommon (two specimens) from Clarksboro Ferry (downstream from Saskatoon) on 3 July 2000 from 300 meters of kick sampling  (i.e. about two specimens per 100 square meters); rare (single specimen) from St. Louis on 8 July 2000 from 300 meters of kick sampling (one specimen per 100 square meters); Saskatoon sewage is a cause that seems obvious for the low numbers downstream from Saskatoon {see Figures 16-23).  Thus, while locally abundant in the year 2000, the areas of high population were very small, and the species could be easily eliminated from the system by destruction of specialized habitat requirements, through dam construction or organic pollution.

 None were found in the North Saskatchewan River in the summer of 2000; the condition of the habitat in the North Saskatachewan appeared to be normal, so the species was probably present, even though not collected.