anteriorly (fig. 14:44a), with the posterior veins weak, 

 the discal cell of characteristic shape, and the anten- 

 nae (fig. 14:440", e,y) of exceedingly variable form. 

 The eggs of some aquatic species are deposited on 

 plants over the water. The larvae (fig. 14:45a-e) are 

 elongate, more or less flattened dorsoventrally, with 

 the head elongate and tapering, much narrower than 

 the body and capable of being retracted halfway with- 

 in the thorax. The body surface is characteristically 

 shagreened, the thickening consisting of a heavy 

 deposit of calcium carbonate secreted by the integu- 

 ment. Respiration is accomplished by a pair of ante- 

 rior spiracles situated on tubercles on the prothorax 

 and by a posterior pair hidden in a transverse, slitlike 

 chamber which opens on the dorsum or the apex of 

 the last segment. In the aquatic species this slit is 

 fringed with long, plumose hairs which serve as a 

 float when the tip of the abdomen is at the water 

 surface, or which support an air bubble when the 

 larva submerges. The aquatic larvae are predom- 

 inantly vegetarians and feed on algae, decaying 

 vegetable matter, and some small microorganisms. 

 Pupation takes place within the last larval skin, form- 

 ing a puparium, with essentially the same characters 

 as the mature larva. Descriptions and figures of 

 aquatic stratiomyid larvae may be found in the papers 

 by Malloch (1917) and Johannsen (1922, 1935). 



Nearly all the known aquatic stratiomyids belong 

 in the subfamilies Stratiomyinae and Adoxomyiinae, 

 which so far as known are entirely aquatic. For this 

 reason, keys to all the North American genera of 

 these two subfamilies are included. 



Keys to the North American Genera of 



Aquatic Stratiomy idae 



Adults 



1. Abdomen with 7 visible segments (BERIDINAE), or 

 antenna terminating in a hairlike arista (GEOSAR- 

 GINAE, PACHYGASTRINAE), or with elbowed distal 

 segment longer than proximal flagellar segments com- 

 bined (HERMETIINAE) Nonaquatic 



— Abdomen with not more than 5 clearly defined seg- 

 ments (fig. 14:446); antenna never terminating in a 

 hairlike arista or with elbowed distal segment longer 

 than proximal flagellar segments combined 2 



2. All posterior veins arising from the discal cell (fig. 

 14:44/) (ADOXOMYIINAE) 3 



— The fourth posterior vein arises from the 2nd basal 

 cell (fig. 14:44a) (STRATIOMYINAE) (key adapted from 

 James, 1936) 9 



3. Scutellum without spines 4 



— Scutellum with spines 5 



4. Face conically produced (fig. 14:44c) 



Nemotelus Geoffroy 



— Face receding below; Florida .. Euryneurasoma Johnson 



5. Antenna short, with a subterminal arista; eastern 

 United States H ermione Meigen (= Oxycera Meigen) 



— Antenna more or less elongate 6 



6. Antennal style not differentiated 7 



— Antennal style distinctly differentiated 8 



7. Antenna with 8 distinct segments, the 2nd not longer 

 than the 1st (fig. 14:44/) Huparyphus Gerstaecker 



— Antenna with 3 segments, the 3rd annulate (not Cali- 

 fornia) Scoliopelta Williston 



8. Eyes hairy; 3rd vein branched .... Adoxomyia Kertesz 



439 

 Wirth and Stone: Diptera 



— Eyes bare; 3rd vein simple; Arizona and New Mexico 



Aochletus Osten Sack«-n 



9. Antenna 10-segmented, those beyond the 2nd more or 

 less fused into a flagellum 10 



— Antenna 7- or 8-segmented, those beyond the 2nd more 

 or less fused into a flagellum (fit;. 14:44c/,*') 11 



10. Tenth antennal segment forming a style; scutellar 

 spines small, preapical, their tips barely reaching the 



apex of the scutellum; Texas to Panama 



Dicyphoma James 



— Tenth antennal segment not stylelike; scutellar spines 

 strong, approximate, equal; Neotropical, one species to 

 Florida Cyphomyia Wiedemann 



11. Face produced conically downward; abdomen slender; 

 usually unicolorous Wyxosargus Brauer 



— Face sometimes protuberant, but not conically pro- 

 duced below the oral margin; abdomen usually with 

 pale tegumentary markings (fig. 14:446) 12 



12. Flagellum of antenna 5-segmented, the apical segments 

 never forming a style; ratio of 1st to 2nd segment 

 usually 2:1 or greater (fig. 14:440") 13 



— Flagellum 6-segmented, the 5th segment short and 

 ringlike, the 6th set at an angle to the rest of the 

 flagellum, segments 5 and 6 forming a definite style; 

 ratio of 1st to 2nd segment less than 2:1 (fig. 14:44e) 



15 



13. Face produced; proboscis elongate; scutellum semi- 

 elliptical, the spines located at the apex on the median 

 3rd 14 



— Face receding; proboscis short; scutellum trapezoidal, 

 the spines located on the outer corners (fig. 14:446) 



Stratiomys Geoffroy 



14. Flagellum flattened; head wider than thorax; eyes 

 angular in profile; spines of scutellum strong; wings 

 infumated in the region of the strong veins; not Cali- 

 fornia H oplitimyia James 



— Flagellum terete; head no wider than the thorax; eyes 

 rounded in profile; spines of scutellum weak or evan- 

 escent; wings hyaline or uniformly infuscated 



Labostigmina Enderlein 



15. Spines of scutellum present, strong and situated within 

 the median 3rd, close together; vein r-m missing or if 

 present, at least 1 of the branches of the media is 

 strongly abbreviated or absent 16 



— Spines of scutellum absent; branches of media well 

 developed; vein r-m present; not California 



Anoplodonta James 



16. Cross vein r-m absent; media with 3 branches, all 

 extending almost to posterior wing margin 



Hedriodiscus Enderlein 



— Cross vein r-m present; at least the 3rd branch of the 

 media much abbreviated Eulalia Meigen 



Larvae and Puparia 



1. Posterior spiracular chamber not margined with long, 

 soft, plumose or pubescent hairs (BERIDINAE, GEO- 

 SARGINAE, PACHYGASTRINAE, and HERMETIINAE) 



Not aquatic 



— Posterior spiracular chamber margined with long, soft, 

 plumose or pubescent hairs 2 



2. Antennae placed dorsally on head remote from margin; 

 last abdominal segment not over twice as long as its 

 basal width (fig. 14:45a-c) (ADOXOMYIINAE) 3 



— Antennae placed at lateroanterior angles of head; 

 last abdominal segment very much longer than broad 

 and tapering (fig. 14:45a>) (STRATIOMYINAE) 5 



3. Posterior margin of ventral side of next to last segment 

 with a pair of stout, curved spines 



Euparyphus Gerstaecker 



— Posterior margin of ventral side of next to last segment 

 without curved, hooklike spines 4 



4. Posterior spiracular chamber located on dorsal side of 

 last segment, the fringe of hairs rather short; last 

 segment emarginate and armed with 4 or 6 long, mar- 

 ginal hairs (fig. 14:456) Nemotelus Geoffroy 



