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Ephemeroptera: Ephemerellidae of Gunnison County, Colorado

Ephemerella dorothea infrequens
Pale Morning Dun, PMD

Needham, 1908

Updated 29 February 2024
TSN 698506

Good Links

On this website:
Introduction to Ephemerellidae
Ephemerella Introduction

Other Websites:
Book Pale Morning Dun, a book by Richard Dokey. The link is to a few paragraphs about the artifical fly imitation that his Grandfather used to tie by hand and his experience of the start of the PMD hatch every year.

Photo Adult male - go to the bottom of the page and among many great photos, there is a Pale Morning Dun or Ephemerella dorothea second from the right.


Alexander,LC; Delion,M; Hawthorne,DJ; Lamp,WO and Funk,DH 2009 Mitochondrial lineages and DNA barcoding of closely related species in the mayfly genus Ephemerella (Ephemeroptera: Ephemerellidae). Journal of the North American Benthological Society, 28(3) 584-595. PDF
     Abstract: "We compared genetic lineages in the mayfly genus Ephemerella (Ephemeroptera: Ephemerellidae) identified from mitochondrial DNA (mtDNA) to current taxonomy in 9 morphological taxa, including 2 geographically widespread species, Ephemerella invaria ( = E. inconstans, E. rotunda, E. floripara) and Ephemerella dorothea ( = E. infrequens). Maximum likelihood and parsimony analyses of the mtDNA sequences placed E. inconstans and E. invaria in a well-supported clade; however, mean Kimura 2-parameter genetic distance between the lineages was high (5.2%) relative to distance within lineages (1.3%). The phylogenetic relationships of synonyms E. rotunda and E. floripara were not resolved, but estimates of mean genetic distance to E. invaria were high for both (8.5% and 11.6%, respectively). Populations of E. dorothea were grouped in 2 well-supported clades (12.9% mean divergence) that did not include the synonym E. infrequens (20.9% mean divergence, based on a single sample). A large genetic distance (18.6%) also was found between eastern and western populations of Ephemerella excrucians. Western samples of Ephemerella aurivillii were so genetically distant from all other lineages (32.2%) that doubt about its congeneric status is raised. mtDNA data have been useful for identifying genetic lineages in Ephemerella, but our results do not support use of cytochrome oxidase I (COI) as a DNA barcode to identify species in this genus because we also found evidence of incomplete mtDNA lineage sorting in this gene. Use of the barcoding gene rediscovered some old taxonomic problems in Ephemerella, a result that emphasizes the importance of completing empirical systematic description of species before using single-character systems for identification."

Allan,JD 1987 Macroinvertebrate drift in a Rocky Mountain stream. Hydrobiologia 144, 261-268.

Buchwalter,DB; Cain,DJ; Clements,WH; Luoma,SN 2007 Using biodynamic models to reconcile differences between laboratory toxicity tests and field biomonitoring with aquatic insects. Environmental Science and Technology 41, 4821-4828.

Courtney,LA and Clements,WH 2000 Sensitivity to acidic pH in benthic invertebrate assemblages with different histories of exposure to metals. Journal of the North American Benthological Society 19 (1) 112-127.Abstract

Gilpin,BR and Brusven,MA 1970 Food habits and ecology of mayflies of the St. Maries River in Idaho. Melanderia 4:19-40. PDF

Jacobus,LM and McCafferty,WP 2003 Revisionary contributions to North American Ephemerella and Serratella (Ephemeroptera: Ephemerellidae). Journal of the New York Entomological Society 111:174-193. PDF
     Abstract: "The study of population variability and the reexamination of type material of certain Ephemerellidae species has revealed changes in status and new synonyms. Ephemerella dorothea Needham, 1908 [=E. infrequens McDunnough, 1924, new synonym, =E. mollitia Seemann, 1927, new synonym] is divided into two subspecies: E. d. dorothea, new status, and E. d. infrequens new status [=E. mollitia, new synonym]. New synonyms were discovered for the following: Ephemerella excrucians Walsh, 1862 [=E. inermis Eaton, 1884, new synonym, =E. argo Burks, 1947, new synonym, =E. crenula Allen and Edmunds, 1965, new synonym, =E. lacustris Allen and Edmunds, 1965, new synonym, =E. rossi Allen and Edmunds, 1965, new synonym, =E. rama Allen, 1968, new synonym], E. invaria Walker, 1853 [=E. rotunda Morgan, 1911, new synonym, =E. vernalis Banks, 1914, new synonym, =E. feminina Needham, 1924, new synonym, =E. fratercula McDunnough, 1925, new synonym, =E. inconstans Traver, 1932, new synonym, =E. choctawhatchee Berner, 1946, new synonym, =E. simila Allen and Edmunds, 1965, new synonym, =E. floripara McCafferty, 1985, new synonym], E. mucronata (Bengtsson), 1909 [=E. moffatae Allen, 1977, new synonym], Serratella micheneri (Traver), 1934 [=E. altana Allen, 1968, new synonym], S. serrata (Morgan), 1911 [=S. sordida (McDunnough), 1925, new synonym, =S. carolina (Berner and Allen), 1961, new synonym, =S. spiculosa (Berner and Allen), 1961, new synonym], and S. tibialis."

Johnson,SC 1978 Larvae of Ephemerella inermis and E. infrequens (Ephemeroptera: Ephemerellidae). Pan-Pacific Entomologist 54, 19-25.
     After the Ephemerella revision by Jacobus and McCafferty in 2003, this paper could be titled "Larvae of Ephemerella excrucians and E. dorothea infrequens."

Kiffney,PM; Clements,WH 1996 Size-dependent response of macroinvertebrates to metals in experimental streams. Environmental Toxicology and Chemistry 15(8)1352-1356.
     Abstract: "Our previous research has shown that the effects of metals on stream benthic invertebrate populations and communities can vary within and between locations. With this in mind, we examined whether invertebrate body size could explain some of the variation in metal sensitivity within a species. Benthic macroinvertebrates from a pristine Rocky Mountain foothills' stream were collected using artificial substrates and exposed to a mixture of Cd, Cu, and Zn in stream microcosms for 10 d at their respective Colorado chronic criterion levels (4.0, 5.0, and 50 mu g/L). The effects of metals on the ephemeropterans Baetis tricaudatus (Baetidae), Ephemerella infrequens (Ephemerellidae), and Rhithrogena hageni (Heptageniidae) and the plecopteran Pteronarcella badia (Pteronarcyidae) were size dependent, as there was an inverse relationship between body size and survivorship. These results may have important implications for setting water-quality criteria for metals and For using benthic invertebrates in biological assessments. "

McCafferty,WP and Provonsha, AV The Mayflies of North America Species List (Version 8Feb2011)
     Here is the geographic range and synonyms:
Ephemerella dorothea infrequens McDunnough, 1924 [CAN:NW;USA:FN,NW,SW]
    * Ephemerella infrequens McDunnough, 1924 (orig.)
    * Ephemerella mollitia Seemann, 1927 (syn.)

McCarty,JD; Cross,WF; Albertson,LK; Tumolo,BB and Sklar,LS 2022 Life histories and production of three Rocky Mountain aquatic insects along an elevation-driven temperature gradient. Hydrobiologia, 849(16), pp.3633-3652. PDF
     Abstract: "Although temperature is known to influence individual traits such as growth, body size, and fecundity, few studies have examined how these relationships influence population-level secondary production in natural settings. We quantified life history traits and production of three dominant aquatic insects (Ephemeroptera: Ephemerella infrequens; Drunella doddsii; Trichoptera: Hydropsyche cockerelli) along an elevation-driven thermal gradient in the northern Rockies. We predicted that production would be highest at sites where temperature regimes lead to the largest terminal body size, individual fecundity, and reproductive potential (i.e., eggs per female x abundance of mature nymphs or larvae). In general, we found that temperature had idiosyncratic effects on life history traits of the study taxa, with no consistent effect of temperature on production. Although growth rates were generally highest during the warm months, growth did not consistently covary with temperature among sites along the elevation gradient. Terminal body size also differed among sites and was inconsistently related to mean temperature and reproductive potential. One of three taxa, D. doddsii, showed patterns entirely consistent with predictions, including smallest body size, reproductive potential, and secondary production at the warmest, low-elevation sites. Our findings suggest that connections among temperature regime, life history characteristics, and secondary production may not be straightforward, and are likely influenced by characteristics unmeasured in our study, including factors that influence survivorship throughout the larval phase, as well as adult mating or oviposition success. Such additional information will enrich our understanding of thermal effects on aquatic insects, and may contribute to predicting how these taxa may respond to ongoing changes in climate."

McDunnough,J 1924. New North American Ephemeridae. Canadian Entomologist 56:221-226.
     Described as Ephemerella infrequens.

Mebane,CA; Schmidt,TS; Miller,JL and Balistrieri,LS 2020 Bioaccumulation and toxicity of cadmium, copper, nickel, and zinc and their mixtures to aquatic insect communities. Environmental toxicology and chemistry, 39(4) 812-833. PDF

Mihuc,TB and Minshall, GW 1995 Trophic generalists vs. trophic specialists: implications for food web dynamics in post-fire streams. Ecology, 76(8), pp.2361-2372.
     Abstract: "The trophic ecology of 11 benthic macroinvertebrate taxa found in Cache Creek, Yellowstone National Park (YNP) was studied to determine if burned organic matter is an important resource and how resource utilization patterns may be altered in post-fire streams. Laboratory food quality experiments were conducted to determine the growth response of each species when grown on several resource types: burned organic matter, periphyton, unburned coarse particulate material (CPM), and unburned fine particulate material (FPM). The central hypothesis of this research was that benthic macroinvertebrates cannot use burned organic matter as a resource. A secondary hypothesis was that some benthic macroinvertebrates are facultative in trophic function, with the ability to use both allochthonous and autochthonous resources for growth. Of the 11 taxa studied, only one (Paraleptophlebia heteronea) could grow on burned organic matter as a resource, indicating that post-fire food webs probably do not exhibit major shifts in resource utilization to burned material. Two species were generalist detrivores (P. heteronea, Ameletus cooki) able to use both natural FPM and CPM resources. Two species were specialist detritivores (Oligophlebodes sigma, Ephemerella infrequens) growing only on unburned CPM resources, and two (Cinygmula mimus, Epeorus albertae) were specialist herbivores utilizing only periphyton. Five species were generalist herbivore-detritivores (Baetis bicaudatus, Drunella doddsi, D. coloradensis, D. spinifera, Zapada columbiana), exhibiting growth on both detritus and periphyton resources. Based on the experimental results, trophic generalists are common food web components in Yellowstone streams. Two of the most abundant benthic macroinvertebrates during post-fire recovery, B. bicaudatus and Z. columbiana, were trophic generalists, indicating that some generalists may be disturbance adapted. In this study, published functional feeding group classification did not indicate obligate resource utilization (growth on only one resource type) for most taxa studied. Comparison of a food web for Cache Creek based on functional feeding group classification and one based on the results of this study indicates that the inclusion of generalists in the web results in a more realistic approximation of food web relationships such as the link-species scaling law. Our results suggest that future research should include spatial and temporal aspects of resource switching and generalist resource utilization by individual lotic primary consumers."

Needham JG. 1908 New data concerning May flies and dragon flies of New York. May flies (Ephemeridae). Bulletin of the New York State Museum 1907:188-194.

Nelson,SM and Roline,RA 1999 Relationships between metals and hyporheic invertebrate community structure in a river recovering from metals contamination. Hydrobiologia 397, 211-226. Abstract
     They studied the Arkansas River above (surface) and below the streambed rocks (hyporheic) before and after a water treatment plant was installed to clean up the Leadville Mine Drainage Tunnel effluent in 1992. At their clean reference site they found Ephemerella pr. infrequens in the surface samples with an average density of 1907 individuals per square meter. The hyporheic samples had a mean density of 881/m².

Newell,RL and Hossack,BR 2009 Large, wetland-associated mayflies (Ephemeroptera) of Glacier National Park, Montana. Western North American Naturalist, 69(3) 335-342. Abstract and PDF

Peckarsky,BL 1983: Biotic interactions or abiotic limitations? A model of lotic community structure. In: Dynamics of Lotic Ecosystems. Eds: Fontaine III,Thomas D; Bartell,Steven M Ann Arbor Science, Ann Arbor, Michigan, 303-323.

Peckarsky,BL 1985 Do predaceous stoneflies and siltation affect the structure of stream insect communities colonizing enclosures? Canadian Journal of Zoology 63, 1519-1530.

Peckarsky,BL 1987a Mayfly cerci as defense against stonefly predation: deflection and detection. Oikos 48(2) 161-170.PDF
     Abstract: "In situ behavioral experiments were conducted in flow-through observation boxes in a Colorado and a New York stream to compare and contrast the cercal responses of Ephemerellidae and Baetidae mayflies to predaceous stoneflies. Ephemerella infrequens (Colorado) exhibited primarily a "scorpion" posture when touched by stoneflies. This posture was stimulated by the touch of any body part of an intact stonefly (antenna, mouthpart, leg, cercus), with some variation in frequency depending on the stonefly, and occurred more often when a mayfly was touched dorsally than on anterior, posterior or lateral body aspects. Scorpion posturing sometimes occurred without physical contact between predators and prey, usually when predators approached Ephemerella from upstream. With increasing size, both E. infrequens (Colorado) and E. invaria (New York) increased the frequency of scorpion posture responses to stoneflies. Very few Ephemerella were consumed by stoneflies during the experiments. Alternatively, the baetid mayfly, Baetis bicaudatus (Colorado) exhibited a "tail curl" posture during which cerci and posterior abdominal segments were flexed laterally in the direction of actively foraging predators. This response always occurred before touch by the stoneflies and usually when predators passed beside the mayflies rather than approached directly from upstream or downstream. Tail curl responses were followed by active swimming, drifting, or crawling by Baetis - behavior that prevented touch encounters between predators or prey. Thus, no Baetis were consumed after a tail curl response. I speculate that while the use of cerci by Ephemerella deflects stoneflies, cerci are used by B. bicaudatus to detect water wave disturbances produced by foraging stoneflies, enabling the prey to avoid predator encounters and thereby reduce the risk of predation."

Peckarsky,BL 1990 Habitat selection by stream-dwelling predatory stoneflies. Canadian Journal of Fisheries and Aquatic Sciences 48, 1069-1076.

Peckarsky,BL 1991a A field test of resource depression by predatory stonefly larvae. Oikos 61(1) 3-10.

Peckarsky,BL 1991b Is there a coevolutionary arms race between predators and prey? A case study with stoneflies and mayflies. Advances in Ecology 1, 167-180.

Peckarsky,BL and Cowan,CA 1995 Microhabitat and activity periodicity of predatory stoneflies and their mayfly prey in a western Colorado stream. Oikos, 513-521. PDF
     Abstract: " Experiments were conducted to determine whether overlap between microhabitat preferences and activity periodicities of four mayfly species and their stonefly predators could explain species-specific differences in predator-prey encounter frequencies. Preferences for rock type (slate or granite), flow microhabitat (high or low), rock surface (top, bottom, upstream or downstream sides), and periodicity of drift and the use of rock tops were measured in a stream-side system of flow-through circular Plexiglas chambers receiving natural stream water and light levels. These parameters were compared among the predatory stoneflies, Megarcys signata or Kogotus modestus, and four species of mayflies that vary in their encounter rates with the stoneflies. Based on predator-prey encounter rates previously observed in similar chambers, we expected greater overlap between Megarcys and Ephemerella infrequens and the overwintering generation of the bivoltine mayfly, Baetis bicaudatus than with Cinygmula sp. Likewise, we expected Kogotus microhabitat use to overlap more strongly with that of summer generation Baetis than with later instars of Cinygmula and Epeorus deceptivus. Results ran counter to our predictions, indicating that microhabitats of the prey species with high predator encounter rates did not overlap more strongly with the stoneflies than did mayflies with low predator encounter rates. Most mayflies and stoneflies preferred the bottom surfaces of granite rocks, and showed few flow preferences. Most were nocturnal in their use of top rock surfaces, in drift and feeding activity periodicity. Therefore, nocturnal activity periodicities of both mayflies and stoneflies confirm that mayflies have not evolved feeding periodicity to avoid encounters with foraging stonefly predators. We conclude therefore, that neither temporal nor spatial microhabitat overlap is a reasonable explanation of differential encounter rates between predatory stoneflies and their mayfly prey. Alternative explanations for differential encounter rates are that more abundant or more mobile mayflies have higher encounter rates with predators, and effective pre-contact predator avoidance responses of other mayflies reduce their encounter rates with stoneflies."

Peckarsky,BL and Penton,MA 1988 Why do Ephemerella nymphs scorpion posture: a "ghost of predation past"?. Oikos, 185-193. PDF
     Abstract: "The behavior of intact Ephemerella infrequens (Ephemeroptera, Ephemerellidae) and Ephemerella with cerci amputated was observed in response to encounters with live predaceous stoneflies (Megarcys signata, Plecoptera: Perlodidae), tethered-live and tethered-model predators, freshly excised stonefly antennae, and thin wires. The incidences of defensive posturing (scorpion posture), movement (crawl, swim, drift) and freezing (no response, stop) behavior were video-taped in response to these predatory stimuli. Scorpion postures occurred with significantly higher frequency when Ephemerella was touched by live and model Megarcys than by Megarcys antennae and wires, with no differences between the two former or the two latter treatments. Frequency of posturing was not altered by prey orientation toward or away from predators or by direction of predator approach with respect to current (upstream, downstream, or beside prey). Thus, hydrodynamic cues associated with live and model Megarcys rather than simple tactile, chemical or visual cues are probably most important in stimulating Ephemerella to scorpion posture. Removal of Ephemerella cerci resulted in a decreased incidence of scorpion posturing, and modification of frequencies of movement and freezing behaviors with predator-prey orientation. These results suggest that cerciless mayflies may have impaired or altered sensory systems. However, cercal removal did not increase Ephemerella's risk of predation, since numbers of intact and cerciless prey consumed during predation trials did not differ. Gut content analysis of Megarcys showed that they were size selective on smaller Ephemerella, which are known to scorpion posture with significantly lower frequency than large Ephemerella. We speculate that the posture is an evolutionary relict, a "ghost of predation past," that is not as effective in smaller individuals, which are also softer-bodied and have smaller spines. Present-day preference for small Ephemerella or other mayfly species over large Ephemerella may be attributed to the historical effectiveness of the scorpion posture, long prey handling times, difficulty in prey capture, or absence of an appropriate behavioral attack stimulus. None of these factors was affected by removal of cerci."

Pennack,RW and Ward,JV 1986 Interstital faunal communities of the hyporheic and adjacent groundwater biotopes of a Colorado mountain stream. Archiv für Hydrobiologie Suppl. 74 3, 356-396.
     They found E. infrequens nymphs in the hyporheic zone of the South Platte river in the Front Range of Colorado at 1863 meters elevation.

Poff,NL and Ward,JV 1991 Drift responses of benthic invertebrates to experimental streamflow variation in a hydrologically stable stream. Canadian Journal of Fisheries and Aquatic Sciences, 48(10): 1926-1936.
     Abstract: Field experiments were conducted in the regulated upper Colorado River to assess drift responses of lotic macroinvertebrates to streamflow manipulations. In each of three seasons, drift was collected in one control and two experimental riffles. On the first day, no flow manipulations occurred. Six hours before sunset on the second day, streamflow was simultaneously reduced and elevated in two experimental riffles with instream diversion structures. Following flow elevation, both mean daily drift density and drift rate generally increased for 13 taxa across all seasons. Flow reductions generally induced elevated drift densities for most taxa, but drift rates declined for some taxa. Patterns of diel drift periodicity were less frequently modified by flow manipulations. Taxa with typical nocturnal peaks in drift activity (Baetis spp., Epeorus longimanus, Triznaka signata) generally maintained this pattern despite some increases in diurnal drift. For a few taxa, modification of diel drift patterns occurred, either as nocturnal decreases following reduced flow (Paraleptophlebia heteronea, Ephemerella infrequens) or as diurnal drift increases in response to either elevated flow (Lepidostoma ormeam, Chironomidae larvae) or reduced flow (Simuliidae). With some exceptions, observed drift responses could be used to suggest active versus passive processes of drift entry.

Rader,RB and Ward,JV 1987 Resource utilization, overlap and temporal dynamics in a guild of mountain stream insects. Freshwater Biology, 18(3), pp.521-528. PDF

Rader,RB and Ward,JV 1989 Influence of impoundments on mayfly diets, life histories, and production. Journal of the North American Benthological Society 8:64-73.

Short,RA; Canton,SP and Ward,JV 1980 Detrital processing and associated macroinvertebrates in a Colorado mountain stream. Ecology, 61(4), 727-732. PDF
     E. infrequens nymphs were found in all 4 of the plant species used to make leaf packs; alder, willow, aspen and pine.

Short,RA 1983 Food habits and dietary overlap among six stream collector species. Freshwater Invertebrate Biology 2:132-138. PDF
     Discussed as Ephemerella infrequens.

Ward,JV and Berner,L 1980 Abundance and altitudinal distribution of Ephemeroptera in a Rocky Mountain stream. In Advances in Ephemeroptera biology (pp. 169-177). Springer US. PDF

Webb,JM; Jacobus,LM; Funk,DH; Zhou,X; Kondratieff,BC; Geraci,CJ; DeWalt,RE Baird,DJ Richard,B Philips,I and Hebert,PDN 2012 A DNA barcode library for North American Ephemeroptera: Progress and prospects. PloS One 7(5): e38063 HTML
      Quote: " ...Ephemerella dorothea infrequens McDunnough, and Teloganopsis deficiens (Morgan) were all monophyletic with a maximum intraspecific divergence greater than the minimum interspecific divergence. "

Brown,WS 2004 Ephemeroptera of Gunnison County, Colorado, USA