Ephemeroptera: Heptageniidae of Gunnison County, ColoradoEcdyonurus (Nixe) criddlei
Criddle's Flat-headed Mayfly, Western Ginger Quills (McDunnough) 1927
Updated 28 September 2025
TSN 100693
Notes
In 2004, McCafferty changed this animal's name from Nixe criddlei to Ecdyonurus criddlei. There are many references to Nixe criddlei, and the older name Heptagenia criddlei, in species lists and the literature of the late 20th century.
Locations Collected
E. criddlei is found across Western Canada and the Western United States down to northern Mexico.
Good Links
On this website:
Nixe criddlei
Other Websites:
Photos, Map, Museum specimens, DNA - Barcodinglife.org
North American distribution map - flyfishingentomology.com
Photos and more from Troutnut
References
Argyle,DW and Edmunds,GF 1962 Mayflies (Ephemeroptera) of the Curecanti Reservoir Basins Gunnison River, Colorado. University of Utah Anthropological Papers 59 (8) 178-189.
Discussed as Heptagenia criddlei.
Bedarik,AF and Edmunds,GF 1980 Descriptions of larval Heptagenia from the Rocky Mountain region (Ephemeroptera: Heptageniidae). Pan-Pacific Entomologist (56) 51-62. PDF
Discussed as Heptagenia criddlei. The authors studied a specimen collected by "Higgins" who collected the larvae from the Gunnison River at Iola on 16 VIII 1949. This was before the Blue Mesa reservoir flooded the site.
Colletti,PJ; Blinn,DW; Pickart,A and Wagner,VT 1987 Influence of different densities of the mayfly grazer Heptagenia criddlei on lotic diatom communities. Journal of the North American Benthological Society 6(4):270-280. PDF
Abstract: "Localized high densities of the mayfly nymph Heptagenia criddlei McD. occur in Oak Creek, Arizona during the summer. We examined the effects of different grazer densities of H. criddlei on diatom cell density and community structure in a laboratory stream over selected time periods ranging from 1 d to 4 wk. Insect densities at 800-1000 nymphs/m2, 2800-4100 nymphs/m2, and 7100-7700 nymphs/m2 of periphyton cover were compared with ungrazed control channels. Our observations show that localized differential grazer densities are important in determining the abundance, composition, and physiognomy of lotic diatom communities. At grazer densities of 800 nymphs/m2 there were no notable differences in diatom abundance and diatom assemblages between grazed and ungrazed systems throughout a 4-wk period. However, major differences were noted after 10 d at 2800 nymphs/m2, 3 d at 4100 nymphs/m2 and within 24 hr at grazing densities ≥7100 nymphs/m2. At grazer densities ≥2800 nymphs/m2 the overall density of diatoms declined and the relative proportions of larger upright diatom species to smaller adnate diatom species decreased through time with increased grazing pressure. Adnately attached diatom taxa like Cocconeis placentula var. euglypta (Ehr.) Cl. and Epithemia adnata (Kütz.) Breb. showed greatest resistance to grazing, while diatoms with smaller cell dimensions like Achnanthes minutissima Kütz. were next most resistant to grazing by Heptagenia. "
Larson,EI; Poff,NL; Atkinson,CL and Flecker,AS 2018 Extreme flooding decreases stream consumer autochthony by increasing detrital resource availability. Freshwater Biology, 63(12), pp.1483-1497. PDF
Quote: "At Coal Creek, a low-elevation stream in the St. Vrain drainage, herbivores, which comprised 11% of the pre-flood community, were absent in our 2014 sampling. The ephemerellid mayfly Drunella grandis, the heptageniid mayfly Ecdyonurus criddlei, and the glossosomatid caddisfly Agapetus sp., all members of the herbivore functional feeding group, were found at the stream in 2011 sampling, but not 2014. Herbivores significantly declined compared to pre-flood abundances both in terms of raw and proportional abundance across the disturbance gradient (raw: b=-641.22, t(6)=-5.183, pt=0.004, F(1,5)=26.87, pF=0.004, R2=0.843; proportional: b=-0.114, t(6)=-2.400, pt=0.062, F(1,5)=5.758, pF=0.062 , R2=0.535; Figure 5)."
McCafferty,WP 2004 Contribution to the systematics of Leucrocuta, Nixe, and related genera (Ephemeroptera: Heptageniidae). Transactions of the American Entomological Society 130(1): 1-9.
The author moves Nixe criddlei into the genus Ecdyonurus because it has all the features of the Ecdyonurus simplicioides species group. Quote from page 3: "For the purposes of recognizing Ecdyonurus in North America, i.e., the simplicioides species group of Ecdyonurus, especially from the closely related genera Leucrocuta and Nixe, it may be diagnosed as having generally plesiotypic larvae with well-developed male eyes, an unmodified pronotum, a gill tuft with two or more filaments present at base of gill lamellae 6 (usually well-developed), and the three caudal filaments with well-developed interfacing setae; and in adults, as having proximate male eyes in addition to having penes (e.g., Fig 98 [Traver 1935], Fig. 4g [Demoulin 1964], Figs 103, 106 ;Jensen 1966]) with divergent lobes that have spines present ventrally, a medially extended lateral sclerite dorsally, narrowly attenuate titillators, and that lack developed dorsolateral spines." He notes that the genera Ecdyonurus, Leucrocuta and Nixe are very similar.
McCafferty,WP; Durfee,RS and Kondratieff,BC 1993 Colorado mayflies (Ephemeroptera): an annotated inventory. Southwestern Naturalist 38 3, 252-274. PDF
Discusses this species as Nixe criddlei. Quote from page 261: "It is likely that some of the Heptagenia spp. reported from the upper Gunnison River drainage system by Argyle and Edmunds (1962) are referable to this species."
McCafferty,WP and Provonsha,AV The Mayflies of North AmericaSpecies List (Version 8Feb2011)
Here is the geographic range and synonyms:
Ecdyonurus criddlei (McDunnough), 1927 [CAN:NW;MEX:SW;USA:NW,SW]
* Ecdyonurus otiosus (McDunnough), 1935 (syn.)
* Ecdyonurus rosea (Traver), 1935 (syn.)
* Ecdyonurus salvini (Kimmins), 1934 (syn.)
* Heptagenia criddlei McDunnough, 1927 (orig.)
* Heptagenia otiosa McDunnough, 1935 (syn.)
* Heptagenia rosea Traver, 1935 (syn.)
* Heptagenia rubroventris Traver, 1935 (syn.)
* Heptagenia salvini Kimmins, 1934 (syn.)
* Nixe criddlei (McDunnough), 1927 (comb.)
* Nixe otiosa (McDunnough), 1935 (syn.)
* Nixe rosea (Traver), 1935 (syn.)
* Nixe salvini (Kimmins), 1934 (syn.)
McDunnough,J 1927 A new Heptagenia from the Yellowstone Region (Ephemeroptera). Canadian Entomologist 59:261.
Described as Heptagenia criddlei
Moody,EK; Corman,JR and Bogan,MT 2016 Caught between a rock and a hard mineral encrustation: long-lived aquatic insects accumulate calcium carbonate deposits in a montane desert stream. Western North American Naturalist, 76(2), 172-179. PDF
Quote from page 177:"Long-lived species that go through many larval instars may be less likely to accumulate CaCO3 encrustation due to their higher molting frequency. Of the aquatic insects, mayflies tend to have particularly high numbers of larval instars (Fink 1980), but only one long-lived mayfly was represented in our stream: Ecdyonurus criddlei. Although the life history of E. criddlei has not been studied, congeneric species pass through at least 18 larval instars (Rawlinson 1939). This high molting frequency might explain why we never found Ecdyonurus with CaCO3 deposits. "
Webb,JM and McCafferty,WP 2008 Heptageniidae of the world. Part II. Key to the genera. Canadian Journal of Arthropod Identification, 7(10.37551). PDF
Quote from page 2:"Notes on the Keys
Most specimens of Heptageniinae and Rhithrogeninae should be readily identified using this key. Differentiation of some Ecdyonurinae genera, however, is more provisional, especially in the poorly known Oriental Region. For larvae of Ecdyonurinae, the relative development of the anterior margin of the head capsule is frequently useful, but may be difficult to interpret. The more primitive genera generally have the dorsal and ventral surfaces of the anterior margin distinctly differentiated (Fig. 34). Afronurus, Darthus, and Parafronurus differ in having a rounded anterior margin where the dorsal and ventral surfaces do not meet in a distinct edge (Fig. 30). Thalerosphyrus and Atopopus have the anterior margin distinctly thickened ventrally, and sometimes dorsally as well (Figs. 31, 36). Larvae of Nixe and the Ecdyonurus simplicioides group cannot reliably be distinguished except by examination of eggs from mature females. In North America, Ecdyonurus simplicioides (McDunnough, 1924a) is known to be sympatric with several Nixe spp. in central Canada, but can be distinguished by the colour pattern of the head capsule, as indicated in the key. Nixe kennedyi (McDunnough, 1924b) is sympatric with
Ecdyonurus in far western North America, but the larva is unknown and so diagnostic characters cannot be provided. In the eastern Palearctic, Nixe joernensis (Bengtsson, 1909) is sympatric with several species of the Ecdyonurus simplicioides group, but there is insufficient information to provide characters that will consistently differentiate Ecdyonurus and Nixe in this region.
The key should correctly identify males of most genera, but some difficulties within the Ecdyonurinae may be encountered due to our lack of knowledge, particularly in the highly diverse and poorly known Oriental realm. The terminology sed for the various spines, sclerites, and titillators of the penes are illustrated in Figure 163."
Fig 109 Ecdyonurus criddlei, Egg chorion,
male penes. Fig. 147 Ecdyonurus criddlei, dorsal,
Zuellig,RE; Heinold,BD; Kondratieff,BC and Ruiter,DE 2012 Diversity and Distribution of Mayflies (Ephemeroptera), Stoneflies (Plecoptera), and Caddisflies (Trichoptera) of the South Platte River Basin, Colorado, Nebraska, and Wyoming, 1873-2010. U.S. Geological Survey Data Series 606, 257 p. PDF - caution 46MB
Quote from page:30 "This species is common in small streams in the foothills of the SPRB. McCafferty (2004) transferred Nixe criddlei into the genus Ecdyonurus." Elevation collected 4,950-9.450 ft. Adults were found July-November.
Zuellig,RE; Kondratieff,BC and Rhodes,HA 2002 Benthos recovery after an episodic sediment release into a Colorado Rocky Mountain river. Western North American Naturalist 62 (1) 59-72.
Discusses this species as Nixe criddlei.
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