10 JAMES BURTON ON A SPECIES OF ALEURODES. 



always four wings, in both male and female. But the chief diSer- 

 ence is in the metamorphosis which the insect passes through. As is 

 well known, much the greater number of Aphides are produced 

 viviparously from unfertilised females, and no true metamor- 

 phosis occurs, though there is some change as the insect develops. 



Dr. Sharp in the Cambridge Natural History, vol. vi., says : 



" These minute insects are at present a source of considerable 

 perplexity owing to the curious nature of their metamorphosis, 

 and the contradictory accounts given of them. In the earlier 

 stages they are scale-like and quiescent, being fixed to the under- 

 side of the leaf. The French authors Signoret and Girard state 

 that the young are hatched having visible appendages and seg- 

 mentation, but that after they are attached to the leaf the organs 

 gradually atrophy. Maskell states the opposite, saying that the 

 organs in the earliest stages are not usually recognisable, but 

 become visible after the growth of the insect. 



" Heeger states that the larva undergoes three ecdyses, and he 

 gives the figures reproduced in the Cambridge Natural History. 

 If he is correct it would appear that the nymph undergoes a great 

 development. Reaumur, on account apparently of their great 

 metamorphosis, treated the species known to him as lepidop- 

 terous, though he correctly pointed out their distinctions. At 

 present we can only conclude that the Aleurodidae undergo a 

 metamorphosis of a kind peculiar to themselves, and requiring 

 renewed investigation 



" Maskell has increased the number of species to about sixty. 

 We have three or four in Britain, one of which, A. brassicae, is ex- 

 tremely abundant on various kinds of cabbage in certain years." 



I have quoted this account because, so far as the species which 

 I have had under observation are concerned, I am able to 

 supply some definite information on doubtful points. 



A writer in The Journal of Micrology says : 



" Another lodger is a very pretty moth-like fly. Its wings are 

 pure white except for a dusky marking on each ; they are covered 



