34 MISC. PUBLICATION 631, U. S. DEPT. OF AGRICULTURE 



17. Small, dirty white, slightly flattened larvae, measuring up to 4 mm., with 



short processes on the dorsal and lateral surfaces ; posterior spiracles 

 on brown, sclerotized tubercles, each with a narrow opening 



(fig. 98) PHORIDAB 



Larger, more nearly cylindrical larvae, with longer, pointed fleshy pro- 

 cesses laterally and dorsally ; posterior spiracles in a cleft on the pos- 

 terior face of the anal segment and consisting of flattened plates per- 

 forated by 3 slits (Chrysomya, in part, fig. 32) __ calliphoridae (in part) 



18. Posterior spiracles at the end of a long, retractile respiratory tube which, 



when extended, is longer than the length of the body proper ; rat- 

 tailed maggots (fig. 90) syrphidae (in part) 



Posterior spiracles on short tubercles or a short respiratory process 

 which is much shorter than the body length 19 



19. Robust larvae, with the body transversely wrinkled, broad behind and 



tapering anteriorly ; posterior spiracles small and situated 

 close together at the apex of a short respiratory tube (Syrphus) 



syrphidae (in part) 



Body form not as above, not strongly wrinkled transversely ; posterior 

 spiracles on separate tubercles or on a forked respiratory process 20 



20. Posterior spiracles at the end of the branches of a forked respiratory 



process; moderately stout larvae (figs. 92 and 93) 21 



Posterior spiracles situated at the apices of short cones ; very slender 

 larvae (fig. 95) 22 



21. Last 2 thoracic segments and first 6 abdominal segments each with a 



spinose ambulatory protuberance, or proleg, on each side 



(fig. 92) ephydridae 



Thoracic and abdominal segments without prolegs drosophilidae 



22. Anal segment with a pair of fingerlike ventrolateral processes ; mature 



larvae do not skip sepsidae 



Anal segment with a pair of ventrolateral processes which are tapered 

 and point slightly upward ; mature larvae move in a skipping 

 fashion piophilidae 



The Family SARCOPHAGIDAE 



The family Sarcophagidae includes a wide variety of biotic types ; 

 among these are the familiar medium-sized grayish flies, with tessel- 

 lated abdomens, that are frequently found around carcasses of dead 

 animals. Many species, however, do not breed in carrion; some are 

 excrement breeders, some parasitize insects, snails, and other inverte- 

 brates, and some breed in decaying vegetable matter. The family con- 

 tains about a thousand described species and without doubt many 

 more that are yet to be described. It occurs throughout the world, 

 except in the polar regions; its members are most abundant in the 

 Holarctic Region but are also well represented in the tropics. 



The family has been treated under different names by certain 

 authors, although the usage employed here is the usual one. Curran 

 (29) unites this family with the Calliphoridae under the name Meto- 

 piidae, while Townsend (153, pt. VI, p. 64) uses the name Stephano- 

 stomatidae. Some species were formerly considered as belonging to the 

 Larvaevoridae (Tachinidae). 



In general the family contains flies of medium size, usually gray 

 with the abdomen frequently marked with checkerboard patterns 

 which change with the light incidence. The eyes are broadly separated 

 in both sexes, although usually the front is somewhat narrower in the 

 male. The mouth parts are well developed. Hypopleural and ptero- 

 pleural bristles are present. The postscutellum is never developed ; its 

 absence will readily distinguish doubtful cases from the Larvaevori- 

 dae. The wing has vein rn x bent strongly forward and ending before 

 the apex of the wing, although the apical cell is in most cases open. 



