502 



DIPTERA 



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

 lower face remains intact. The account of the pupation given 

 by 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 any head-vesicle. Nothing is known as to 

 the details of the life of these anomalous larvae. M. Poujade 

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

 ant Lasius niger? The larva we figure was found by Colonel 

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



FIG. 239. Larva of Microdon sp. Portugal. A, Dorsal view of the larva, x 4 ; 1, 

 the stigrnatic structure ; B, posterior view of stigmatic structure ; C, a portion of 

 the marginal friiige of the body. 



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

 flies themselves are scarce, Microdon mutabilis (formerly called 

 M. apiformis) 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 legs 

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

 Microdon has been observed by Verhoeff ; 3 he noticed that the fly 

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

 sanguinea but returned undiscouraged to its task. 



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

 nas been given by Perils, 4 and he also gives some information as 

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



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



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



3 Ent. Nadir, xviii. 1892, p. 13. 4 Ann. Soc. ent. France (4) x. 1870, p. 330. 



