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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Stratiomyidae - Marsh Flies

[under construction]

Key to adults
(adapted from James 1981)

1a a. Crossvein m-cu absent 2
b. Cell dm present also: Antennal flagellum composed of six flagellomeres; branches of M often weakened; body variegated in background
1b a. Crossvein m-cu present 5
b. Cell d present
2a(1a) a. Antenna short, with the last two flagellomeres forming a distinctly preapical arista Oxycera Meigen
2b a. Antenna of ordinary length, much shorter than the three basal flagellomeres combined 3
3a(2b) a. R4 fused with R3 Euparyphus (Aochletus) Osten Sacken
b. Cell r3 fairly short and broad, with the membrane no more than 4-5x as long as its maximal width
c. Aedeagus bifid
also: Veins outlining cell dm apical to CuA2 and crossvein r-m feeble, concolorous with membrane
3b a. R4 separate from, or fused with, R5 4
b. If R4 fused with R5, then the membrane of cell r3 at least 6x, but usually 8-10x, as long as its maximal width
c. Aedeagus bifid or trifid
4a(3b) a. Spines of scutellum usually separated at its base by a distance at least as great as the length of the spines Caloparyphus James
b. If length of separation smaller, then the apical 1/4th of wing with only scattered microtrichia, and with extensive bare areas along the veins
c. Aedeagus trifid
d. Robust, with abdomen usually black, and either with median spots, or with transverse, usually interrupted, bands
4b a. Spines of scutellum always closer together at its base than the length of the spines Euparyphus (Euparyphus) Gerstäcker
b. Apical 1/4th of wing thickly and uniformly covered with microtrichia
c. Aedeagus bifid
d. Slenderer than above, and abdomen not mark as above
also: Penultimate flagellomere of antenna subequal to the preceding one; facial pattern without a black or brown median area or vitta and yellow lateral margin
5a(1b) a. A1 slightly though distinctly sinuous Myxosargus Brauer
b. Face produced angularly downward at the lower margin
c. Abdomen relatively slender, no more than 2/3 wide as long, and not patterned
5b a. A1 not sinuous 6
b. Face sometimes tuberculate or somewhat produced forward, but never downward
c. Abdomen at least 3/4x wide as long, usually patterned

6a(5b) a. Scutellum without spines Anoplodonta James (may not be valid record - check)
b. Venation strong
c. M1, M3, and crossvein r-m all present and distinct
6b a. Scutellum with spines, in Labostigmina sometimes minute 7
b. Venation variable
7a(6b) a. Antenna with 5 flagellomeres, without a stylus Stratiomyini, 8
b. Ratio of scape to pedicel > 2:1
c. Venation variable
7b a. Antenna with 6 flagellomeres, the last two flagellomeres forming a short but distinct stylus Odontomyiini, 9
b. Ratio of scape to pedicel not more than 1.5:1
c. Venation somewhat reduced, either crossvein r-m absent, or at least M3 reduced to a stump or weak fold, sometimes virtually absent
8a(7a) a. Face receding Stratiomys Geoffroy
b. Scetullar spines strong, located on the outer corners and outside the median third


a. Face produced or tuberculate, if tuberculate then the tubercle involves the area of antennal insertion Labostigmina Enderlein
b. Scutellar spines weak or evanescent
also: Flagellum cylindrical or almost so, scape 1.25-2.5x as long as pedicel; head not wider than thorax
9a(7b) a. Wing with crossvein r-m absent, M1 and M3 strong and distinct nearly to wing margin Hedriodiscus Enderlein
9b a. Wing with crossvein r-m present, M3 and sometimes M1 weak, reduced to a stump or fold, or virtually absent Odontomyia Meigen, 10
10a(9b) a. Pleural, postpronotal, and supra-alar regions in female, and usually in male, marked with distinct yellow areas Odontomyia (Odontomyia) Meigen
10b a. Pleural, postpronotal, and supra-alar regions wholly black or without distinct yellow areas in both sexes 11
11a(10b) a. Abdomen black in background, with transverse paired yellow or green linear or triangular markings at the tergal apices Odontomyia (Catatasina) Enderlein
11b a. Abdomen yellow or green in background, usually with a median longitudinal black stripe dorsally, the stripe sometimes occupying most of the dorsum but leaving broad lateral margins pale Odontomyia (Odontomyiina) Enderlein

Key to larvae
(adapted from Courtney et al. 1995) [Anoplodonta and Labostigmina not keyed]

1a a. Spirical cleft situated dorsally near apex of the last abdominal segment and, if with bordering hydrofuge setae, very short and inconspicuous Nemotelus Geoffroy
1b a. Spirical cleft at apex of the last abdominal segment with long marginal hydrofuge (water repelling) setae 2
2a(1b) a. Antennae situated dorsolaterally on the head capsule, and directed dorsally 3
2b a. Antennae situated anteriolaterally on the head capsule, and directed anteriorly or somewhat ventrally 6
3a(2a) a. Hydrofuge setae arising from 2 lobate structure on the lower lip of the spiracular cleft Myxosargus Brauer
b. Anterior spiracles located at the anterior corner of the prothorax
3b a. Hydrofuge setae arising from straight edge of the lower lip, with the spiracular cleft lacking strong lobate structures 4
b. Anterior spiracles located laterally near the middle of the prothorax
4a(3b) a. Terminal abdominal segment almost rectangular in outline, with its posterior margin more or less indented or sublaterally notched Oxycera Meigen
4b a. Terminal abdominal segment subconical in outline, with rounded lateral and posterior margins 5
5a(4b) a. Anterior spiracle on a short stalk, or nearly sessile Caloparyphus James
5b a. Anterior spiracle on a long stalk Euparyphus Gerstacker
6a(2b) a. Terminal abdominal segment long and slender, it apical portion with its lateral margins nearly parallel Stratiomys Geoffroy
b. Terminal abdominal segment with anus located anteriorly and swollen
6b a. Terminal abdominal segment rarely over twice as long as wide, uniformly posteriorly tapered 7
b. Terminal abdominal segment with anus not conspicuosly swollen
7a(6b) a. Ab7 lacking sclerotized hooklike spines on the posterior margin Odontomyia (Catatasina Enderlein)
b. Integument covered with minute peltate scale-like pubescence
7b a. Ab7 with sclerotized hooklike spines on the posterior margin 8
b. Integument pubescence variable
8a(7b) a. Only Ab7 with hooked spines Odontomyia (Odontomyiina Enderlein)
8b a. Ab6-7 with hooked spines Odontomyia (Odontomyia Meigen), Hedriodiscus Enderlein


Courtney GW, Teskey HJ, Merritt RW, Foote BA. 1995. Aquatic Diptera. Part One. Larvae of Aquatic Diptera, pp. 484-548 in Merritt RW, Cummins KW. An Introduction to the Aquatic Insects of North America, 3rd Edition. Kendall/Hunt Publishing, Dubuque, Iowa, USA.
James MT. 1981. Stratiomyidae, pp. 497-511 in McAlpine JF, Peterson BV, Shewell GE, Teskey HJ, Vockeroth JR, Wood DM. Manual of Nearctic Diptera. Volume 1. Research Branch Agriculture Canada. Monograph No. 27.