Ephemeroptera: Baetidae of Gunnison County, ColoradoAcentrella insignificans(McDunnough) 1926Updated 27 May 2025
TSN 568572 DescriptionLarvae are 2-tailed, the center filament is a stub of one or two segments. Legs have a dense row of long fine setae. Being two-tailed with hind wing pads, makes them similar to Baetis bicaudatus. Their labial palp lacks a thumb and they have long setae on their legs which separates Acentrella insignificans from B. bicaudatus. The hind wing pads separate them from A. turbida.Locations CollectedGunnison River and Taylor River above Taylor Reservoir.NotesPreviously referred to as Baetis insignificans. Common in western Colorado and across the western United States.Good LinksOn this website:Acentrella turbida Acentrella Introduction Other websites: Photos, Map, Museums, DNA - Barcode of Life Data System North American distribution map - flyfishingentomology.com ReferencesAllen,RK and Murvosh,CM 1987 New Baetidae from the southwestern United States and northern Mexico (Ephemeroptera: Insecta), with notes. Canadian Entomologist 119, 1095-1099.Discussed as Baetis insignificans. Quote from page 1095: "This species is widely distributed in western North America, and is known to occur from Alberta and British Columbia to Arizona, New Mexicao and northern Mexico" 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. Heinold,B 2010 The mayflies (Ephemeroptera), stoneflies (Plecoptera), and caddisflies (Trichoptera) of the South Platte River Basin of Colorado, Nebraska, and Wyoming. M.S. Thesis, Colorado State University, Fort Collins, CO 375 pages. 148 distribution maps. PDF Remarks about A. insignificans from page 30: "Most literature refers to this species as Baetis insignificans (McCafferty et al. 1993). This transcontinental species is common throughout the foothills and plains section of the SPRB and apparently can tolerate moderate siltation and lower flows. Larvae can be collected most of the year. Specimens were collected from 865 m to 2439 m in elevation. Adults were present from May through July. " McCafferty,WP; Durfee,RS; Kondratieff,BC 1993 Colorado mayflies (Ephemeroptera): an annotated inventory. Southwestern Naturalist 38 3, 252-274. PDF The Purdue University Entomological Collection (PERC) has specimens from the Gunnison River. Quote from page 254: "This species is known throughout the west. Although it is known from all physiographic regions of Colorado, it is a particularly common mayfly in far western Colorado streams and rivers. " McCafferty,WP and Provonsha, AV The Mayflies of North AmericaSpecies List (Version 8Feb2011) Here is the geographic range and synonyms: Acentrella insignificans (McDunnough), 1926 [CAN:FN,NW;MEX:SW;USA:FN,NE,NW,SW]
Baetis insignificans McDunnough, 1926 (orig.)
McDunnough,J 1926 New Canadian Ephemeridae with notes. IV. Canadian Entomologist 58:296-303. Described as Baetis insignificans. 
 Waltz RD and McCafferty,WP 1987 Systematics of Pseudocloeon, Acentrella, Baetiella, and Liebebiella, new genus (Ephemeroptera: Baetidae). Journal of the New York Entomological Society 95:553-568. 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. They found this species in the Gunnison River. The United States Geological Survey (USGS) National Water Quality Assessment Data Warehouse (NAWQA) shows this species is present in Gunnison County. Data as of 1Sep2005 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 18: "Remarks: This transcontinental species is common throughout the foothills and plains section of the SPRB and apparently can tolerate moderate siltation and lower flows. Larvae can be collected most of the year. Most previous literature refers to this species as Baetis insignificans (for example, McCafferty and others, 1993)." The elevation range is 2,850-8,000 ft and adults are found May-July. "Satisfaction of one's curiosity is one of the greatest sources of happiness in life."
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