174 AJV A ceo UNT OF BRITISH FLIES. 



clinging feet. There are also a pair of pediform' appendages figured 

 on the last segment, analogous to those in fig. 37 of CJiironomus 

 plumosiis^ and also four branchial appendages on the same segment, 

 with two tufts of hairs in addition. These larvffi grow rapidly, so that 

 within six or seven days they are four to five times their original length. 

 After the third moult the larva is one third of an inch long, its head 

 becomes smaller, and its feet elongated ; the skin acquires a very 

 delicate rose colour, caused by the development of the pupal skin 

 beneath. The movements of the larva gradually lessen and eventu- 

 ally cease ; it then casts its skin, and the pupal stage is reached. 

 The pupa is three m. long, with long head, described by Grumm 

 as not unlike that of a cat, with 9-jointed abdomen, and the six legs 

 on the thorax, and bent around the wing cases. The abdomen is 

 covered by many small paired hairs and longer single setae. The 

 sides of the abdomen exhibit long dark brown bands, which terminate 

 in the penultimate segment in a small bunch of claw-like processes. 

 On the last but one segment are two apertures, and between and 

 below them a third, the anal orifice. There are also two groups of 

 delicate hairs on the last segment. The thorax is dilated dorsally 

 into a shield covering the head above ; at the sides of the thorax the 

 wing-cases are visible. Prominent pyriform eyes are also seen, 

 between which lie the antennae. Above the head are two thick fila- 

 ments ; these are no doubt branchiae (resembling those seen in the 

 pupa of Corethra plumicornis). No stigmata are of course seen in 

 these aquatic forms. Such is briefly the structure of the Chironoinus 

 larva and pupa observed by Grumm, in which asexual reproduction 

 was observed to take place. We remember in the case of the 

 Cecidomyidcv, the asexual generations were produced by the Cecid 

 larvre (p. 42), and that the larvae producing the asexual generations 

 eventually themselves turned to perfect insects. But in the case of 

 the Chirono7nidce we find things very different ; it is not the larva 



Fig. 38. — Eggs of Chiroiiomu%. 



that has the asexual reproduction, but the pupa ; neither are living 

 young (maggots or pupa;) produced but ova, whereas in Cccidomyia 

 living larvEC were produced. The two holes above the anus 

 described in the pupa are the orifices through which the eggs are 



