MUSOIDEA. 97 



Muscidea. — Proboscis functional or rndimentary, in the for- 

 mer case usually short and with pseudotraclieate labella, but 

 sometimes elongate and adapted for piercing ; palpi sometimes 

 rudimentary, never jointed. Antennae always three-jointed, 

 the third joint simple, round, oval or elongate, compressed, 

 and always (except Cryptocliwtum, where it is entirely absent) 

 with a bare, pubescent or plumose, dorsal or subapical arista. 

 Auxiliary vein sometimes rudimentary, often more or less 

 coalescent with the first longitudinal vein, distinct in its entire 

 course ; never more than one submarginal and three posterior 

 cells present, the marginal and submarginal cells aways open ; 

 Basal cells never large, the second basal cell sometimes co- 

 alescent with the discal cell, the anal cell present or absent ; 

 posterior cross-vein rarely absent. Pulvilli always present; 

 empodia wanting; claws of the male often larger than those 

 of the female. 



The largest flies are found among the Calyptratse, especially 

 the •Tachinidge and Sarcophagida^, but the largest do not equal 

 the largest of the OrthorrhaJ)lia. Commonly the flies belong- 

 ing to the Acalyptratse are of moderate size or small, often 

 indeed minute. The habits are of course very diverse, but by 

 far the largest number live among rank vegetation, and are 

 generally caught in sweepings. 



The larvae in a few forms are hatched from the eggs in the 



body of the parent fly ; the pupae are always inclosed in the 



contracted, hardened, larval skin, known as the puparium, the 



top of which is sprung off like a lid by the aid of the ptUinum, 



an inflatable organ })ushed out through the frontal suture, 



which is characteristic of the group. In their habits, the 



larger part of those of the Calyptratae are parasitic upon 



other insects, the (Estridae upon warm-blooded animals. 



Many of the larvae of the Sarcopliagidie, Muscidae and An- 



thomyidae live in decomposing animal matter or in living 



or decomposing vegetable matter as do also nearly all of the 



Acalypti'atjc. 



12 



