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Ephemeroptera: Heptageniidae of Gunnison County, Colorado

Introduction to the mayfly genus Rhithrogena
Red Quills, Western March Browns

Eaton 1881
Updated 22 Jun 2021
TSN 100572
The recently emerged Rhithrogena female subimago or dun was photographed in the Cement Creek drainage on 21July2008. This animal will molt once more to become a sexually mature imago.

Species List


Allen,RK; Chao,ESM 1978 Mayflies of the Southwest: new species and records of Heptageniidae. Pan-Pacific Entomologist 54, 311-315. PDF

Blackadar,RJ; Baxter,CV; Davis,JM and Harris,HE 2020 Effects of river ice break-up on organic-matter dynamics and feeding ecology of aquatic insects. River Research and Applications, 36(3) 480-491. PDF
     Abstract: "Disturbance shapes the structure and function of aquatic communities and ecosystems, but the dynamics of ice are a less studied dimension of the disturbance-regime of rivers. We investigated effects of a river-ice regime on organic-matter dynamics and feeding ecology of aquatic insects. Samples of biofilm and aquatic insects for gut content analysis were collected monthly from Big Creek, a sixth - order tributary of the Middle Fork Salmon River in central Idaho, USA, during winter 2010-2011. Our results indicate that river ice affects both quantity and quality of organic matter available to, and used by, consumers. Specifically, scour from December and February ice break-up events reduced biofilm biomass by one-half and one-third, respectively, whereas quality (chlorophyll-a: ash-free dry mass) increased. Diets of scrapers, Rhithrogena (Heptageniidae) and Bibiocephala (Blephariceridae), collector-gatherers, Baetis (Baetidae), and collector-filterers, Simulium (Simulidae) appeared to follow patterns of organic matter. Following ice break-up events, diets of these taxa had increased proportions of diatom frustules, which are high-quality food resources due to their relatively high nutrient content. Other taxa, such as collector-gatherers, non-Tanypodinae (Chironomidae), and the collector-filterer, Arctopsyche grandis (Hydropsychidae), consistently consumed high proportions of diatom frustules and insect material, respectively, suggesting they were able to feed more selectively throughout winter. Our study indicates that ice regimes in temperate rivers can affect organic-matter dynamics and feeding ecology of aquatic insects, a possibility that deserves additional investigation, particularly in light of potential changes to the ice regimes of rivers with changing climate."

Brinkman,SF and Johnston,WD 2008 Acute toxicity of aqueous copper, cadmium, and zinc to the mayfly Rhithrogena hageni. Archives of Environmental Contamination and Toxicology 54:3, 466-472. Abstract

Buchwalter,DB; Cain,DJ; Martin,CA; Xie,L; Luoma,SN; Garland,JT 2008 Aquatic insect ecophysiological traits reveal phylogenetically based differences in dissolved cadmium susceptibility. Proceedings of the National Academy of Sciences 105 24, 8321-8326.

Codreanu,R 1927 Le cycle évolutif d'un Chironomide a larve ectoparasite d'une nymphe d´Ephémère. C. R. Société Biol., Paris, 96:1433-1435. PDF

Dodds,GS 1923 Mayflies from Colorado: descriptions of certain species and notes on others. Transactions of American Entomological Society 69, 93-116. PDF

Durfee,RS and Kondratieff,BC 1994 New additions to the inventory of Colorado mayflies (Ephemeroptera). Entomological News 105(4):222-227. PDF
     Quote from page 223: "The adults of R. pellicuda can easily be separated from the other four species of Rhithrogena in Colorado by their distinctive genitalia (Fig. 1) and small size. The larvae of R. pellicuda can be separated from the other species of Colorado Rhithrogena by the absence of a dorsal lobe on gills 2-6 (present on R. hageni Eaton, and R. undulata [Banks]), and the absence of a longitudinal ventral sclerotized setose line on gills 2-6 (present on Rhithrogena robusta Dodds) (Jensen 1966). In addition, the larvae of R. pellicuda have a characteristic V-shaped transparent marking on the ventral gill surface that points out perpendicular to the long axis of the body. Although the larvae of R. flavianula are unknown, the much larger size of the adults (body length 14mm) (McDunnough 1924), should make mature larvae of this species easily separable from the much smaller R. pellicuda (body length 6-7mm). "

Eaton AE 1881 An announcement of new genera of the Ephemeridae. Entomologist's Monthly Magazine 18:21-27.
     The genus Rhithrogena is described on pages 23 and 24.

Edmunds GF Jr. 1952b Studies on the Ephemeroptera. Part II. The taxonomy and biology of the mayflies of Utah Unpublished Ph.D. Thesis, University of Massachusetts 399 pages.

Gill,BA; Harrington,RA; Kondratieff,BC; Zamudio,KR; Poff,NL and Funk,WC 2014 Morphological taxonomy, DNA barcoding, and species diversity in southern Rocky Mountain headwater streams. Freshwater Science 33(1) 288-301.
     Working in wadeable streams on the Front Range of Colorado, they found a cryptic species of Rhithrogena as well as R. robusta.

Jensen,SL 1966 The Mayflies of Idaho (Ephemeroptera). M.S. Thesis, University of Utah, Utah. 364 p.
     Quote from page 188: "The following combinations of characters serve to distinguish this genus from all other genera of Heptageniidae occuring in Idaho: Adults. (1) Basal segment of the fore-tarsi of the male one fourth or less as long as the second segment; (2) stigmatic crossveins more or less anastomosed (Fig. 72), or if only slighty anastomosed, the femora have a dark streak of color present; and (3) subanal plate of the female broadly rounded, without a postero-median emargination. Mature nymphs. (1) Three well developed caudal filaments; and (2) gills on abdominal segments one and seven enlarged, meeting beneath the abdomen to form a ventral disc (Fig 83). "

Mebane,CA; Dillon,FS and Hennessy,DP 2012 Acute toxicity of cadmium, lead, zinc, and their mixtures to stream-resident fish and invertebrates. Environmental Toxicology and Chemistry, 31(6), 1334-1348. PDF

Rebora, M., Piersanti, S. and Gaino, E., 2009 The antennal sensilla of adult mayflies: Rhithrogena semicolorata as a case study. Micron, 40(5-6)571-576. PDF
     Abstract: " The present paper reports on an ultrastructural investigation of the sensilla on the antennal flagellum of the imago (SEM and TEM) and subimago (SEM) of the mayfly Rhithrogena semicolorata. Sensilla coeloconica of two different sizes, named big and small pegs, are distinguishable in both stages. The big pegs are lobe-shaped with a porous cuticle. The small pegs are more or less conical with a smooth cuticle. TEM seriate sections revealed that the big pegs are innervated by three neurons, which enter the peg. The dendrite sheath opens at the entrance to the peg and leaves the dendrites in contact with the outside through pores and pore tubules. This structure is in agreement with that reported for single-walled olfactory receptors. The small pegs may be innervated by two or four neurons. In both cases, two unbranched dendrites enter the peg and are in close association with the peg wall. These show features typical of hygroreceptors. In the small pegs innervated by four neurons, the other two neurons stop short of entering the peg, and one of them branches. This last could constitute the thermoreceptive unit. The function of the fourth neuron is unknown.The presence of olfactory sensilla in adult mayflies, such as Paleoptera, is relevant to the study of evolutionary trends in insect odour perception. Hygro-thermoreceptors are important in such fragile aquatic insects, which need a moist environment for moulting and reproduction."

Schmidt,TS; Clements,WH; Zuellig,RE; Mitchell,KA; Church,SE; Wanty,RB; San Juan,CA; Adams,M; Lamothe,PJ 2011 Critical tissue residue approach linking accumulated metals in aquatic insects to population and community-level effects. Environmental science and Technology, 45(16) 7004-7010. PDF
     Abstract: "Whole body Zn concentrations in individuals (n = 825) from three aquatic insect taxa (mayflies Rhithrogena spp. and Drunella spp. and the caddisfly Arctopsyche grandis) were used to predict effects on populations and communities (n = 149 samples). Both mayflies accumulated significantly more Zn than the caddisfly. The presence/absence of Drunella spp. most reliably distinguished sites with low and high Zn concentrations; however, population densities of mayflies were more sensitive to increases in accumulated Zn. Critical tissue residues (634 μg/g Zn for Drunella spp. and 267 μg/g Zn for Rhithrogena spp.) caused a 20% reduction in maximum (90th quantile) mayfly densities. These critical tissue residues were associated with exposure to 7.0 and 3.9 μg/L dissolved Zn for Drunella spp. and Rhithrogena spp., respectively. A threshold in a measure of taxonomic completeness (observed/expected) was observed at 5.4 μg/L dissolved Zn. Dissolved Zn concentrations associated with critical tissue residues in mayflies were also associated with adverse effects in the aquatic community as a whole. These effects on populations and communities occurred at Zn concentrations below the U.S. EPA hardness-adjusted continuous chronic criterion."

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

Stanford JA; Gaufin AR 1974 Hyporheic communities of two Montana rivers. Science 185:700-702. PDF
     The authors report Rhithrogena sp. nymphs from the hyporheic zone of the Flathead River in Montana, USA.

Brown,WS 2004 Mayflies (Ephemeroptera) of Gunnison County, Colorado, USA