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

 The Genus MUSCINA Robineau-Desvoidy 



The genus Myxoma may be distinguished from other common Mus- 

 cidae by the following combination of characters : The body is robust, 

 brownish or black in ground color, with rather dense grayish pollen, 

 which, on the abdomen, is changeable with the light incidence; the 

 apex of the scutellum is more or less extensively reddish or yellow ; 

 the arista is long plumose ; the proboscis is short and the labella fleshy ; 

 the eyes are bare; the wings are uniformly hyaline, without noticeable 

 yellowing at the base; vein m 1+2 is distinctly bowed forward, but the 

 bow is broad and not sharply bent ; anterior acrosticals are present in 

 two rows; and the pteropleura are bare. The adults bear some super- 

 ficial resemblance to certain Sarcophagidae, but the lack of hypopleural 

 bristles will at once distinguish them. 



Life Histories. — The adults feed on various substances, but chiefly 

 juices from meats, fruits, and vegetables which are spoiling or fer- 

 menting. The larvae breed in various types of media, including 

 fungi, decaying or diseased vegetable matter, bodies of dead insects, 

 snails, and vertebrates, and, as parasites, on living insects and verte- 



Figure 76. — Muscina stabu- 

 lii us, first-stage larva. After 

 Seguy (134, P- 312).) 



Figure 77. — Muscina stabulans, pos- 

 terior spiracles of pupariuin. 



brates. Several species attack nestling birds. In their food habits 

 they are characterized in Keilin (66, p. 437) as omnivorous and are 

 considered by him as transitional between the saprophagous and the 

 truly parasitic muscids, such as Passeromyia. 



Eggs are deposited upon the breeding medium. There are three 

 larval stages; in the last stage, the larvae become highly voracious and 

 carnivorous, and destroy other dipterous larvae with which they come 

 in contact. Pupation occurs within a cocoon formed from debris sur- 

 rounding the transforming larva. 



Larva. — The larva is of the usual muscoid type, slender and pointed 

 anteriorly, and gradually broadening posteriorly. The first-stage 

 larva (fig. 76) is translucent, its internal organs being clearly visible 

 through the integument ; it is smooth and glabrous, without complete 

 rows of spinules, but with small ventral spinulose areas anteriorly on 

 at least most of the abdominal segments. The mouth is surrounded 



