I ) 1 1'T E K A M U SC 1 D.E. 551 



Family MUSCID^e Leach. 

 MUSCA Linne. 



Under this head I have temporarily placed five species of dipterous 

 larva- which appear to belong to this family. 



Nearly all of them, however, and especially Musca ascarides, so closely 

 resemble the larvae of bot-flies that I could scarcely persuade myself that 

 they did not. belong to the (Kstmho. The appendages of the skin, how- 

 ever, are much more delicate than is usual in (Estridae, and are uniformly 

 distributed over the surface or are altogether absent. The empty skins, 

 too, have every appearance of belonging to the same insects as the com- 

 plete hodies, and, although these are not cast skins (in which case they 

 would be proved natural inhabitants of the water), for they still contain 

 the harder parts of the internal organs in many cases, but rather remains 

 of partial! v decomposed larvae, it would seem improbable that so large a 

 number of cestrid larvae could be found, when the only way in which they 

 could have reached their present condition would be through the dropping- of 

 animals affected by the bots , standing in the water. Of course the refer- 

 ence I have given them is only provisional. 



MUSCA ASCARIDES. 



I'l. 5, Figs. 74, 75, 79, 82-87, 98, 101. 

 Musca cucarides ScuiW., Bull. II. S. Geol. Geo<;r. Surv. Terr., Ill, 7'>G-7f>7 (1677). 



First there is a species to which a considerable number of specimens 

 belong, which may take the name here given. Some of the specimens are 

 complete: others consist of emptied skins only. When contracted the 

 bodv is thick, especially on the anterior half, and about twice as long as 

 broad, closelv resembling the larva of a bot-fly. Both extremities are 

 rounded, the anterior verv broadlv, while the posterior half tapers very reg- 

 ularly. In one specimen, which is not so much shrunken, the body is 

 fusiform, and about three and a half times longer than broad, the head 

 and hinder extremity tapering in a nearly equal degree. In the emptied 

 skins, as in the others, it mav be seen that the normal form is a blunt, 

 squarely rounded head, behind which the body is nearly equal, and then 

 tapers toward the tail. At the anterior extremity may be nearly al\\.i\- 

 seen a portion of the mandibles, consisting of a pair of very slender rods or 



