Aquatic Insects of Michigan

by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
University of Michigan

Stenochironomus (Chironominae, Chironomini) of Michigan - Identification

Key to Adults
(modified from Borkent 1984)

1a Wing with a distinct, transverse, medial band, always discrete from the more basal and more apical pale membrane; Femur and tibia of at least the fore and hind legs partially to completely pigmented 2
1b Wing without a discrete medial band; Legs without pigmentation except for all fifth tarsomeres, which are sometimes pale brown ; also: Wing without pigmentation; palpus pale; male antennae with all hairs pale; anal point of male with dorsal edge straight in lateral aspect, and with parallel-sided apex in dorsal aspect; female with spicules on ventrolateral lobe weakly developed and not on a pronounced swelling Stenochironomus macateei (Malloch)

2a(1a) Wing with apical band extending into cells R3 and CuA1; Appendage 2 of male with apical seta shorter and basally thicker than subapical seta; Apex of anal point either parallel-sided or bulbous from dorsal view; also: Pigmentation of legs light to dark brown; male with basal 0.12 to entire fore tibia pigmented, or female basal 0.18 to entire fore tibia; Gc/Gs of male 0.82-0.98; female with inner half of lateral apodeme of S IX not markedly swollen Stenochironomus hilaris (Walker)
2b Wing with apical band not extending into cells R3 or CuA1; Appendage 2 of male with apical seta either shorter and basally thicker, or nearly as long and basally as thick as subapical seta; Apex of anal point parallel-sided from dorsal view 3

3a(2b) Hind femur with pigmentation restricted to apical 0.13-0.73 of femur length; also: Wing of male with pigmentation anterior of arculus; female with area between C and M veins pigmented; male with apical 0.23-0.28, female with apical 0.19-0.69 of hind femur pigmented; male with length of Cu/M = 1.02-1.11 and Hd Ta1/Ti = 0.78-0.88; female with wing length/length of M = 2.34-2.51; M with 2-9 setae, Hi Ta1/Ti = 0.78-0.88 and palp segment 3/4 = 1.28=1.46 Stenochironomus pulchripennis (Coquillett)
3b Entire hind femur pigmented but some specimens with a subapical pale annulus; also: Male with entire fore femur pigmented and with extreme base and subapical annulus pale; Ant. 13/1-12 = 1.93-2.48; female with subapical annulus 0.05-0.14 of total fore femur length Stenochironomus poecilopterus (Mitchell)

Key to Pupae
(modified from Borkent 1984)

1a Respiratory organ with horn mostly fused with anterior trunk, with free portion small; with or without clear, anteriorly bilobed area on posterior margin of S II and S III; also: T II with posterior row of hooklets usually without a median gap Stenochironomus hilaris (Walker)
1b Horn of repiratory organ arising near base, elongate thin, extending beyond multiforked portion of anterior trunk; S II and S III uniformly yellowish brown 2

2a(1b) Spur on S VIII with 1-2 deltoid lateral teeth and 2-5 sharply pointed, smaller median teeth, each more than 1/4 length of the largest tooth; Terminal filaments of respiratory organ stout (> 4µ in diameter), forking near apices Stenochironomus macateei (Malloch)
2b Spur on S VIII with 2-6 deltoid to elongate lateral teeth of similar size of similar size or with most lateral teeth smaller than those in midregion of spur, and with 1-3 elongate, smaller, medial teeth; Terminal filaments of respiratory organ thinner than above (<4µ in diameter), forking subapically Stenochironomus pulchripennis (Coquillett), Stenochironomus poecilopterus (Mitchell)

Key to 4th Instar Larvae
(modified from Borkent 1984)

1a Mandibular adductor apodeme with posterior dark pigmentation; Ligula with very fine shagreen, extending posteriorly to, or nearly to, the lateral edge of base of lobe, defined posteriorly in most specimens by a discrete border; Paralabial plate wider than portion of maxilla to which it is fused; also: Anal papillae without constriction 2
1b Mandibular adductor apodeme with no posterior dark pigmentation; Ligula with very fine to scale-like shagreen, not extending posteriorly to the lateral edge of base of lobe, or rarely, extending to the lateral edge, not defined or defined posteriorly by a discrete border; Paralabial plate and a portion of maxilla with which it is fused, of approximately equal width 3

2a(1a) Head capsule length 534-698 µ; Distance of antennal seta from base/length of antennal segment 1 = 0.63-0.72 Stenochironomus poecilopterus (Mitchell)
2b Head capsule length 592-776 µ; Distance of antennal seta from base/length of antennal segment 1 = 0.68-0.82 Stenochironomus pulchripennis (Coquillett)

3a(1b) Spicules of pecten epipharyngis in a short, medially-placed row but grouped medially; head capsule length 407-640 µ; Ligular lobes joined or not joined by coloration; Distance of antennal seta from base/length of antennal segment 1 = 0.48-0.71 Stenochironomus macateei (Malloch)
3b Spicules of pecten epipharyngis in a longer row, extending laterally to bases of chaetulae laterales; head capsule length 533-756 µ; Ligular lobes joined by coloration; Distance of antennal seta from base/length of antennal segment 1 = 0.69-0.83 Stenochironomus hilaris (Walker)

References

Borkent A. 1984. The systematics and phylogeny of the Stenochironomus complex (Xestochironomus, Harrisius, and Stenochironomus)(Diptera: Chironomidae). Memoirs of the Entomological Society of Canada 128:1-269.

Page created: November 11, 2005 - Last updated: November 9, 2013 (EB)