S02 



DIPTERA 



CHAP. 



separated from the anterior part of the upper surface, while the 

 lower face remains intact. The account of the pupation given 

 1 IV Elditt ^ is not complete : the two horns that project are, it 

 would appear, not portions of the larval skin, but belong to 

 the head of the pupa, and according to Elditt are used to effect 

 the dehiscence of the case for the escape of the fly ; there does 

 not appear to be anj^ head-vesicle. Nothing is known as to 

 the details of the life of these anomalous larvae. i\I. Poujade 

 has described two species foiind in France in the nests of the 

 ant Zasins niger.^ The larva we figure was found by Colonel 

 Yerbiiry in nests of an Atta in Portugal, and an almost identical 



. X 4 ; 1, 

 portion of 



Fig. 2.39. — Larva of Microdon sp. Portugal. A, Dorsal view of the larva, 

 the stigraatic .structure ; B, posterior view of .rtigmatic structure ; C, a 

 the marginal fringe of the body. 



larva was recently found by Mr. Budgett in Paraguay. The 

 flies themselves are scarce, Microdon mutabilis (formerly called 

 M. cqnformis) being one of the rarest of British flies. They have 

 the antennae longer than is usual in Syrphidae, and the cross- 

 veins at the outside of the wing are irregularly placed, so that 

 the contour is very irregular : the resemblance to bees is very 

 marked, and in some of the South American forms the hind leo-s 

 are flattened and hairy like those of bees. The oviposition of 

 Mvrodon has been observed by Yerhoeff ;^ he noticed that the fly 

 was frequently driven away by the ants — in this case, Formica 

 sanguined — \mt returned undiscouraged to its task. 



A brief resume of the diverse modes of life of Syrphid larvae 

 has been given by Perris,* and he also gives some information as 

 to the curious horns of the pupae, but this latter point much 



^ Ent. Zeit. Stettin, vi. 1845, p. 384, pi. i. 



" Ann. Soc. ent. France (6) iii. 1883, p. 23, pi. i. 



■' Ent. Xadir. xviii. 1892, p. 13. •* Ann. Soc. ent. France (4) x. 1870, p. 330. 



