Ephemeroptera: Siphlonuridae of Gunnison County, ColoradoSiphlonurus occidentalis
Dark Grey Drake, Gray drake, Light Grey Drake, Primative Minnow Mayflies (Eaton, 1885)
Updated 26 Sept 2024
TSN 100955
Locations Collected
Gunnison River, Soap Creek, West Elk Creek, Red Creek, Dry Gulch, Tomichi Creek (Argyle and Edmunds, 1962)
Good Links
Photos, Map, Taxon Identifier Numbers - from the Global Biodiversity Information Facility Siphlonurus occidentalis at Gbif
Photos, Map, Museum specimens, DNA - Barcodinglife.org
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.
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 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. "
Brittain,JE and Saltveit,SJ 1989 A review of the effect of river regulation on mayflies (Ephemeroptera). Regulated Rivers: Research & Management, 3(1), pp.191-204. PDF
Abstract: "Impoundment and diversion of watercourses for power production and water supply can have profound effects on the mayfly fauna. To explain such effects a species-specific approach is adopted on account of differing habitat requirements and life histories in the order and even within genera. Environmental conditions such as discharge and flow patterns, temperature, food availability, and predation may be changed. This leads to changes in the density and species composition of the mayfly community, especially when there is a hypolimnion drain from reservoirs. Temperature changes below such reservoirs may remove obligatory life cycle thresholds. Prolonged periods of low discharge lead to the dominance of genera, such as Paraleptophlebia, Choroterpes, Siphlonurus, and Pseudocloen, typical of slow-flowing and lentic habitats.
The life cycle plasticity and opportunism shown by Baetis rhodani in Europe and B. tricaudatus in North America have undoubtedly contributed to their success in regulated rivers. The life history characteristics of Tricorythodes are also advantageous below dams. The increased growth of periphyton and mosses below many dams favour certain Ephemerellidae, but restrict or eliminate many Heptageniidae. In order to survive adverse conditions, flexible life cycles or a short period of rapid nymphal growth coupled with a long period of egg development, are advantageous."
Buchwalter,DB and 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
Quote from page 515: "It appears that structural expansion is variously apportioned to the subimaginal and adult molts in mayflies. Nixe criddlei tarsi are 1.83 times longer than those of the larva in the subimago and 2.61 times longer than those of the larva in the adult; Siphlonurus occidentalis tarsi are 2.0 and 2.9 times he larval length in the subimago and adult, respectively;"
Quote from page 522: "The speed with which subimagos were able to right themselves after being
placed on their side with wings contacting water varied immensely among subimagos of different genera observed (G. F. Edmunds,Jr. and T. J. Fink,
unpublished). The results could be based on differences in hydrofuge capacity, differences in behavioral response among mayflies, or both. Siphlonurids (Siphlonurus, Ameletus, Parameletus) were slow to respond, and most of the individuals, especially of Siphlonurus, were entrapped on the surface. Heptageniids (Stenacron, Nixe, Heptagenia) righted themselves faster than the siphlonurids and almost always escaped successfully. Leptophlebiids (Paraleptophlebia) and ephemerellids (Ephemerella, Drunella) responded rapidly and escaped so fast that sometimes it was impossible to see if they righted themselves before taking flight"
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,PP and Harper,F 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 and McCafferty,WP 1995 Annotated inventory of the mayflies (Ephemeroptera) of Arizona. Entomological News 106 3, 131-140.
McCafferty,WP; Durfee,RS and 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 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
Quote from page 171: "The nymphs of 29 species of Ephemeroptera from six families were collected during the study. A few additional species not found as immatures in riffles (e.g. Siphlonurus occidentalis Eaton) were collected in sweep nets."
Ward,JV and 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
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)." Elevation collected 4,950-10,950 ft. Adults were found April-August.
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