VII SYRPHIDAE HOVER-FLIES 50I 



of the comb of wasps containing pupae, and again found that the 

 flies did not attack the Hymenoptera ; but on breaking a pupa 

 of the Wasp in two, the fly-larvae attacked it immediately and 

 eagerly ; so that the evidence goes to show that the VoIwcUa- 

 larvae act as scavengers in the nests of the Hymenoptera. 

 Kiinckel d'Herculais has pu1:)lished an elaborate work on the 

 European VoluccUa ; it is remarkable for the beauty of the 

 plates illustrating the structure, anatomy and development, but 

 throws little direct light on the natural history of the Insects. 

 V. homhylans, one of the most abundant of our British species, 

 appears in two forms, each of which has a considerable resem- 

 blance to a Bomhus, and it has been supposed that each of the 

 two forms is specially connected with the Bee it resembles, but 

 there is no evidence to support this idea ; indeed, there is some 

 little evidence to the contrary. The genus Merodon has larvae 

 somewhat similar to those of Volucdla, but they live in l)ull)S 

 of Narcissus; M. equestris has been the cause of much loss to the 

 growers of Dutch bulbs ; this Fly is interesting on account of its^ 

 great variation in colour ; it has been described as a whole series 

 of distinct species. 



The most remarkable of the numerous forms of Syrphid larvae 

 are those, of the genus Microdon (Fig. 239), which live in ants' 

 nests. They have no resemblance to Insect -larvae, and when 

 first discovered were not only supposed to be little Molluscs, but 

 were actually described as such under the generic names of 

 Parmida and Scutclligcra. There is no appearance of segmenta-- 

 tion of the body ; the upper surface is covered by a sort of 

 network formed by curved setae, which help to retain a coating 

 of dirt ; there is no trace externally of any head, but on the 

 under surface there is a minute fold in which such mouth-organs 

 as may be present are probal)ly concealed ; the sides of the l)ody 

 project so as to form a complex fringing arrangement ; the ter- 

 minal stigmata are very distinct, the lateral processes connected 

 with them (the " Knospen " of Dr. Meijere), are, however, very 

 irregular and placed at some distance from the stigmatic scar. 

 Pupation occurs by the induration of the external covering and 

 the growth from it, or rather through it, of two short horns in 

 front. Inside this skin there is formed a soft pupa, of the kind 

 usual in Cyclorrhaphous flies ; the dehiscence of the external 

 covering is, however, of unusual nature, three little pieces being 



