Aquatic Insects of Michigan
by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
University of Michigan
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- Keys/Identification
- Aquatic Insects of Michigan
Chironomidae - Subfamilies
Key to Adults
(Adapted from Coffman
and Ferrington 1996, Cranston 1995, Oliver and Dillon 1989, and Saether 1977)
| 1a | a. Antennae often plummose, with a narrow scape, globular pedicle, and a number (usually 11-14) of cylindrical flagellomeres | Males, 2 |
| b. Ab9 tergite often with a posteromedian extension forming a distinctive anal point | ||
| c. Genitalia located at posterior end of abdomen, with paired claspers, comprising a basal gonocoxite and an apical or subapical gonostylus, and with medial volsellae (mesal appendages) | ||
| 1b | a. Antennae without plummosity, with a smaller pedicle, often with fewer, more flask-shaped flagellomeres than above | Females, 10 |
| b. Variously modified lobes on abdominal gonocoxites VIII and IX, some of which are reduced to sclerotized apodemes | ||
| males | ||
| 2a(1a) | Macropterous, veins and crossveins distinct | 3 |
| 2b | Brachypterous or apterous, veins and crossveins indistinct | 8 |
| 3a(2a) | Wing with crossvein MCu present | 4 |
| 3b | Wing with crossvein MCu absent | 7 |
| 4a(3a) | R2+3 absent, with R1 and R4+5
widely separated |
Podonominae |
| 4b | R2+3 present, or R1 and R4+5 narrowly separated, by no more than width of a vein | 5 |
| 5a(4b) | a. R2+3 forked into R2 and R3 |
Tanypodinae |
| b. If R+3 absent, then wing with many macrotrichiae | ||
| 5b | a. R2+3 simple, unforked | 6 |
| b. Wing with few macrotrichiae, if any | ||
| 6a(4b) | a.
Wing with FCu usually proximal to crossvein MCu |
Diamesinae |
| b. If FCu opposite or slightly distal to crossvein MCu, then wing short | ||
| c. Tarsomere 4 usually cordiform | ||
| 6b | a. Wing with FCu opposite or distal to crossvein MCu | Prodiamesinae |
| b. Wing never shortened | ||
| c. Tarsomere 4 never cordiform | ||
| 7a(3b) | a. Foreleg with fore tarsomere
longer than, or subequal to, tibia |
Chironominae |
| b. Gonostylus less flexibly attached, or rigidly fused, to the gonocoxite, directed backwards | ||
| c. If gonostylus movable and/or fore tarsomere 1 subequal or slightly shorter than fore tibiae, then spurs of mid and hind tibiae often comb-like, consisting of free spiniform setae (spines) | ||
| 7b | a. Fore tarsomere 1 always shorter than fore tibiae | Orthocladiinae |
| b. Gonostylus movable and usually folded inward | ||
| c. Hind tibial comb, when present, consisting of free spiniform setae | ||
| 8a(2b) | a. Gonostylus rigidly fused
to gonocoxite |
Chironominae |
| b. Fore tarsomere 1 longer than fore tibiae | ||
| 8b | a. Gonostylus movable and usually folded inward | 9 |
| b. Fore tarsomere 1 shorter than fore tibia | ||
| 9a(8b) | a. Eye densely hairy |
Diamesinae |
| b. Tarsomere 4 cordiform and shorter than tarsomere 5 | ||
| 9b | a. Eye usually bare or pubescent, sometimes hairy | Orthocladiinae |
| b. If hairy, then tarsomere 4 simple, longer than tarsomere 5 | ||
| females | ||
| 10a(1b) | R2+3 absent, R1 and R4+5 widely
separated |
Podonominae |
| 10b | R2+3 present, or R1 and R4+5 narrowly separated, by no more than width of a vein | 11 |
| 11a(10b) | Gonocoxite IX fused with tergite
IX to form an annular gonotergite |
Tanypodinae |
| also: Gonotergite IX weak, narrow and strap-like, with few or no setae | ||
| 11b | Gonocoxite separated from tergite IX | 12 |
| 12a(11b) | Wing with crossvein MCu present |
13 |
| 12b | Wing without crossvein MCu | 14 |
| 13a(12a) | a. Wing with FCu usually proximal
to crossvein MCu, except on shortened wing, where it may be opposite
or distal to MCu |
Diamesinae |
| b. Tarsomere 4 usually cordiform | ||
| 13b | a. Wing with FCu opposite or distal to crossvein MCu, wing never shortened | Prodiamesinae |
| b. Tarsomere 4 never cordiform | ||
| 14a(12b) | a. Foreleg with basitarsus
longer than or subequal to tibia |
Chironominae |
| b. Spurs of mid and hind tibiae often comb-like, comprising fused spines | ||
| 14b | a. Foreleg with basitarsus shorter than tibia | Orthocladiinae |
| b. Tibial spurs, if comb-like, composed of free spines | ||
| also: midleg shorter than hindleg; usually with 2 spermathecae (sometimes 3 in some genera) | ||
Pupae
(adapted from Cranston 1995, Ferrington and Coffman 1996)
| 1a | a. Anal lobe fringed with setae, but lacking more distinctive macrosetae | Chironominae |
| b. Postero-lateral corner of Ab8 usually with a spur or comb | ||
| c. Thoracic horn often complex, bi- to multibranched, often plumose, but simple only in Tanytarsini and some Pseudochironomini | ||
| 1b | a. Anal lobes with or without setae fringe, if fringed, then nearly always 3 distinctive macrosetae apical/subapical among the fringe | 2 |
| b. Postero-lateral corner of Ab8 never with a comb or spur | ||
| c. Thoracic horn simple or absent, never two-branched from base to plumose | ||
| 2a(1b) | Thoracic horn present (except when damaged, but remnant stem is often visible), with horn sac and a conspicuous plastron plate | 3 |
| 2b | Thoracic horn may be absent, but when present, without a horn sac of plastron | 4 |
| 3a(2a) | a. Two pairs of frontal setae | Podonominae |
| b. Some lateral and anal lobe setae may be 'wavy' | ||
| c. Anal lobe macrosetae often distally located, smaller or spinelike and frequently more than two, but never with a fringe of setae | ||
| d. Sheaths of fore- and midlegs straight, terminating beside recurved hindleg sheath at apex of wing sheath | ||
| 3b | a. One pair of frontal setae on the cephalothorax | Tanypodinae |
| b. Lateral and anal lobe setae not 'wavy' | ||
| c. Anal lobe with 2 macrosetae inserted approximately in the middle third of the lobe margin, or the anal lobe with a fringe of setae or spines along the margin | ||
| d. Aall leg sheaths recurved beneath wing sheath | ||
| 4a(3a) | a. Dorsomedian area of thorax with 3 setae, dc3 typically in supra-alar position, dc4 absent, or all dorsocentral setae absent | Diamesinae |
| b. Fore- and midleg sheaths extend directly backward, hindleg sheath recurved beneath wing sheath | ||
| 4b | a. Dorsomedian area of thorax with 4 setae, with neither dc3 nor dc4 in supra-alar position | 5 |
| b. Typically all leg sheath recurved beneath wing sheath | ||
| 5a(4b) | a. Usually large species, often > 8 mm in length | Prodiamesinae |
| b. Thoracic horn prominent, with indirect connection to adult spiracle | ||
| c. Anal lobe with either (i) full fringe of long setae and usually 4-5 marginal macrosetae, (ii) 3 marginal macrosetae, or (iii) short fringe and 2 small median setae | ||
| d. Ab2 tergite without hookrow, and no abdominal tergites with transverse bands of stronger spines | ||
| 5b | a. Usually smaller species, often < 5 mm in length | Orthocladiinae |
| b. Thoracic horn smaller, without connection to adult spiracle | ||
| c. Anal lobe quite variable, with or without fringe, usually with 0-3 macrosetae | ||
| d. If with more macrosetae than in c, then Ab2 tergite with a hookrow and/or abdominal tergites spinose | ||
Larvae
(adapted from Cranston 1995 and Ferrington
and Coffman 1996)
| 1a | a. Antenna retractile into head | Tanypodinae |
| b. Prementohypopharngeal complex with a distinctive 4-8 toothed ligula | ||
| c. Mentum usually weakly sclerotized, or with dorsomental teeth arranged in conspicuous plates or longitudinal rows | ||
| 1b | a. Antenna non-retractile | 2 |
| b. Ligula never developed as above, without a toothed ligula | ||
| c. Mentum usually entirely toothed and darkly sclerotized | ||
| 2a(1b) | a. Procerci long, at least 5x long as wid | Podonominae |
| b. Premandibles absent | ||
| c. Antennal segment 2 and/or 3 often annulate (seen under high magnification) | ||
| d. Mandible usually with 6 inner teeth next to enlarged apical tooth | ||
| 2b | a. Procerci variable, usually < 3x long as wide, but rarely > 4x long as wide | 3 |
| b. Premandibles almost always present, usually well-developed and conspicuous | ||
| c. Antennal segments not annulate (except Diamesinae, below) | ||
| d. Mandible usually with < 6 inner teeth | ||
| 3a(2b) | a. Mentum associated with distinct, broad ventromental plates (except Stenochironomus with some hooks) that have striations throughout for more than one-half their width | Chironominae |
| b. Eyespots usually separate and in vertical plane, but sometimes dorsal eyespot situated anterior to ventral eyespot | ||
| a.Ventromental plates vestigial to developed, when well developed never with striations (occasionally setae lie underneath) | 4 | |
| b. Eyespots most often single | ||
| 4a(3b) | a. Third antennal segment often annulate (seen under high magnification) due to reduced sclerotization | Diamesinae |
| b.Central ligula and lateral paraligulae of prementum resembling three brushes | ||
| c. If antennae not annulate, then mentum and anterior labral region with large scales similar to figure | ||
| 4b | a. Antennal segments not annulate | 5 |
| b. Prementum never developed as three brushes | ||
| c. Mentum and anterior labral region not as above | ||
| 5a(4b) | a. Ventromental plates elongate, with beard beneath | Prodiamesinae |
| b. Mentum as in figures below | ||
| 5b | a. Ventromental plates variable, if large then never with beard beneath as above | Orthocladiinae |
| b. Mentum not as above | ||
References
Cranston 1995
Ferrington and Coffman 1996
Saether 1975
Page created: March 05, 2004 - Last updated: April 11, 2006 (EB)