The Life Historji of Brilus fiavescens. 49 



Larva (b) hatched on July 22nd, and on July 25th 

 entered the first shell, in which it became entangled, and 

 died without moulting. 



Larva (c) hatched on July 25th, entered the first shell 

 on July 26th, and, after partly devouring the occupant, 

 left it and attacked a second on July 28th ; was ejected 

 some hours afterwards by the latter, and left entangled ; 

 I released it and put it back on the first shell, which it 

 at once re-entered, but it afterwards died without having 

 moulted. 



I have nevertheless found the exuviiE of the young 

 larva at about 3 ram. in very small snail-shells (3-4 mm. 

 in diameter), and it seems more probable that the economy 

 of the larva in its infancy is the same as in its later growth, 

 and that under ordinary circumstances the first shell is 

 not left till after moulting, in the usual manner. It would 

 thus be able to attain a length of about 4 mm. at the 

 time of entering the second shell, at which point it is to 

 be found feeding, about the middle of September, prior 

 to hibernation. After this, the growth of the larva is 

 regulated by the size of the snails it happens to meet 

 with, its length being increased, as I have found in most 

 cases observed, roughly by about half the greatest diameter 

 of the snail attacked. The female imago may thus be 

 no more than 8 mm. in length, or, on the other hand, 

 probably not far short of 30 mm. On the Downs, larger 

 snails such as H. cantiana are seldom met with by the 

 larva, and the average length of nine naturally-reared 

 females which emerged this year was 10'7 mm. only. 



In regard to the life history of the male, Mulsant 

 mentions the fact that out of one hundred and fifty shells 

 containing larvae, Desmarest obtained only two males, 

 while M. Rouget obtained only one male among about 

 two hundred females. Appended are a few details bearing 

 on this point. 



As already mentioned, all of five larvae which I reared 

 in 1900 were females. 



The shells collected in the autumn of 1901 and early 

 in 1902 varied from 4 to 12 mm. in their greatest 

 diameter {i.e. the measurement across the shell to the 

 outermost point of the orifice). Of those larvse that were 

 full-fed, nine were females and five were males. All of 

 the females emerged, but four of the males died as pupse 

 (the fifth was taken in February ; the others in September). 



TRANS. ENT. SOC. LOND. 1903. — PAllT I. (APRIL) 4 



