Ephemeroptera: Baetidae of Gunnison County, Colorado
Introduction to the Mayfly genus AcentrellaBengtsson, 1912
Minature Blue Winged Olive, Small Minnow Mayflies, Minute Graywinged Brown
Updated 18 Nov 2018
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Photos from Troutnut
Regarding the nymphs, both species lack a "thumb" on their labial palp which separates them from Baetis. They both have long setae on the backs of their legs as you can see in the photo below. A. insignificans has hind wing pads while A. turbida does not.
Bengtsson,S 1912 Neue Ephemeriden aus Schweden. Entomologisk Tidskrift 33:107-117.
Burian,SK and Myers,LW 2011 A new species of Acentrella Bengtsson (Ephemeroptera: Baetidae) from New York and New England (USA), redescription of the nymph of A. parvula (McDunnough), and key to known adult males of Nearctic Acentrella. Aquatic insects, 33(4)305-334.
Abstract: " A new species Acentrella rallatoma (type locality: Connetquot River, Oakdale, NY, USA) is described from nymphs and reared adults. Additional specimens were studied from southeastern New York, southeastern New Hampshire, coastal Connecticut, and Martha's Vineyard, MA, USA. Nymphs can be separated from those of other Nearctic species by: scraper-like outer incisors of mandibles, cerci alternately banded from bases to tips, and row of robust bristle-like setae (with modified tips) on dorsal edge of femora. Male imagos can be separated from those that lack hind wings by: distinctive colour pattern of abdominal terga, and genitalia with pigmented sclerotised penes cover. Comparative analysis of A. rallatoma with other Nearctic species revealed a lack of comparative data on nymphs of its presumptive sister species A. parvula. To facilitate future studies of this group, the nymph of A. parvula is redescribed and regional differences are discussed. Abdominal colour patterns of A. parvula that vary over its range from Florida, USA to Labrador, Canada are illustrated. Problems concerning genus-level diagnostic characters for Acentrella nymphs and adults are discussed to facilitate placement of future taxa. To complement existing keys to Nearctic nymphs of Acentrella a provisional key to the known adult males is given."
Jacobus,LM and McCafferty,WP 2006 A new species of Acentrella Bengtsson (Ephemeroptera: Baetidae) from Great Smoky Mountains National Park, USA. Aquatic Insects 28:101-111. PDF
They describe a new species (Acentrella barbarae) and provide a key to the larvae of the seven North American Acentrella species.
Kluge,NJ; Novikova,EA 2011 Systematics of the mayfly taxon Acentrella (Ephemeroptera: Baetidae), with description of new Asian and African species. Russian Entomological Journal 20(1) 1-56.PDF
Lugo-Ortiz,CR and McCafferty,WP 1998 A new North American genus of Baetidae (Ephemeroptera) and key to Baetis complex genera. Entomological News 109 5, 345-353. PDF
McCafferty,WP and Waltz,RD 1990 Revisionary synopsis of the Baetidae (Ephemeroptera) of North and Central America. Transactions of American Entomological Society 116, 769-799. PDF
Waltz,RD 1994 Field recognition of adult Acentrella and Heterocloeon (Ephemeroptera: Baetidae). Great Lakes Entomologist 26(4):321-323.
The author shows that adult Acentrella and Heterocloeon have an anterior process on their mesothorax. This is distinctive for these two genera. Or in plain english, Acentrella adults have a bump on their back just in front of their wings, which is not present in any other local adult mayflies.
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.
Wang,TQ and McCafferty,wp 1996 New diagnostic characters for the mayfly family Baetidae (Ephemeroptera). Entomological News 107 2, 207-212. PDF
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