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Ephemeroptera: Siphlonuridae of Gunnison County, Colorado

Siphlonurus occidentalis
Dark Grey Drake, Gray drake, Light Grey Drake, Primative Minnow Mayflies

(Eaton) 1885

Updated 19 Nov 2020
TSN 100955

Locations Collected

Gunnison River, Soap Creek, West Elk Creek, Red Creek, Dry Gulch, Tomichi Creek (Argyle and Edmunds, 1962)

Good Links


Argyle,DW; Edmunds,GF 1962 Mayflies (Ephemeroptera) of the Curecanti Reservoir Basins Gunnison River, Colorado. University of Utah Anthropological Papers 59 8, 178-189.
     Quote from page 181: "Nymphs of this species occurred in ponds and pools originally part of the stream or in heavily vegetated parts of the stream. They are not ususally found where fish can prey on them. The species is not abundant because of the relative scarcity of suitable habitat in this area. The single imago collected was taken outside of the expedition headquarters building. "

Buchwalter,DB; Luoma,SN 2005 Differences in dissolved cadmium and zinc uptake among stream insects: mechanistic explanations. Environmental Science and Technology 39, 498-504.

Detmer,TM; McCutchan Jr,JH and Lewis Jr,WM 2017 Predator driven changes in prey size distribution stabilize secondary production in lacustrine food webs. Limnology and Oceanography, 62(2)592-605. PDF

Eaton AE. 1883-1888. A revisional monograph of recent Ephemeridae or mayflies. Transactions of the Linnean Society of London, Second Series, Zoology 3:1-352, 65 pl.
     Described as Siphlurus ocidentalis by the Reverend on pages 218 and 219. [Unfortunately this plate is very faint and I couldn't copy the illustration.]

Edmunds,GF 1962 The food habits of the nymphs of the mayfly Siphlonurus occidentalis. Proceedings of the Utah Academy of Science, Arts and Letters 37, 73-74.

Edmunds Jr,GF and McCafferty,WP 1988 The mayfly subimago. Annual review of entomology, 33(1)509-527. PDF
     Scanning electron microscope image in Figure 1 of ventral view of S. occidentalis subimago wing surface showing marginal cilia and surface falcate microtrichia.

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

Harper, P.P. and F. Harper. 1997 Mayflies (Ephemeroptera) of the Yukon. Pp. 152-167 In: H.V. Danks and J.A. Downes, eds. Insects of the Yukon. Biological Survey of Canada (Terrestrial Arthropods). Ottawa, Ontario, Canada. http://www.biology.ualberta.ca/bsc/pdf/harper.pdf

Jensen,SL 1966 The Mayflies of Idaho (Ephemeroptera). M.S. Thesis, University of Utah, Utah. 364 p.
     Quote from page 105: "Nymphs of this species occur in slow flowing rivers and streams or in cooler ponds and lakes. They are usually found on silted bottoms or smong submerged vegetation, especially in rivers where they occur along the edges. They have been collected at elevations of from 3000 to 9000 feet and in water with summer daytime temperaturesof from 45°to 64°F. Edmunds (1964b:74) conducted an interesting study on the food habits of the nymphs and made the following conclusion: "It appears that the nymphs of Siphlonurus occidentalis are omnivorous, feeding on plant and insect remains, and capturing slow moving soft-bodied bottom-feeding insects whenever they get the opportunity."
The adults usually swarm in mid-morning oe evening although they will swarm in midday when it is cloudy. At one locality, one-half mile north of Mackay, male imagos were collected swarming late in the evening about 20 to 30 feet above the highway. Early the next morning female imagos were collected as they were ovipositing up and down the Big Lost River. The female invariably oviposits in riffles in the stream and apparently the eggs hatch the following spring. Adults and nymphs have been collected from mid-May to mid-October."

Lugo-Ortiz,CR; McCafferty,WP 1995 Annotated inventory of the mayflies (Ephemeroptera) of Arizona. Entomological News 106 3, 131-140.

McCafferty,WP; Durfee,RS; Kondratieff,BC 1993 Colorado mayflies (Ephemeroptera): an annotated inventory. Southwestern Naturalist 38 3, 252-274. PDF
     Quote from page 253: "This is a wide-ranging western species (see Allen and Chao, 1981). It is perhaps the most common Siphlonurus in the West. Larvae of this species can often be collected in great numbers in overflow areas of streams throughout Colorado. This was one of the species that had been reported from the pre-impoundment study of the Gunnison River by Argyyle and Edmunds (1962). Although Ward and Stanford (1990) could not find this species in their post-impoundment study of that river, there are specimens housed at CSU and PERC that have been taken from the area since the impoundments were created. "

McCafferty,WP and Provonsha, AV The Mayflies of North AmericaSpecies List (Version 8Feb2011)
     Here is the geographic range and synonyms:
Siphlonurus occidentalis (Eaton), 1885 [CAN:FN,NW:MEX:FS,SW;USA:FN,NW,SW]
    * Siphlonurus inflatus McDunnough, 1931 (syn.)
    * Siphlurella occidentalis (Eaton), 1885 (comb.)
    * Siphlurus occidentalis Eaton, 1885 (orig.)

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; Encalada,AC and McIntosh,AR 2011 Why do vulnerable mayflies thrive in trout streams?. American Entomologist, 57(3), pp.152-164. PDF

Ward,JV; Stanford,JA 1990 Ephemeroptera of the Gunnison River, Colorado, USA. In: Mayflies and Stoneflies. Ed: Campbell,IC Kluwer Academic Publishers,215-220.

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 (No. 606). US Geological Survey. PDF - caution 46MB
      Elevation collected 4,950-10,950 ft. Adults were found April-August. Remarks from page 37: "Larvae of this widespread Western North American species often occur in slow streams and pools and can have a wide elevational distribution (Jensen, 1966; Allen and Chao, 1981; Harper and Harper, 1997)."

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