HOP-FLY. 71 



and fly about and enjoy themselves, and, what seems 

 scarcely credible, the winged females lay eggs, and whilst 

 this operation is going on, a solitary, winged blight may 

 be observed on the under-side of the leaves, or on the 

 young shoots, particularly on the hop, and differing from 

 all its own progeny, in being winged and nearly black, 

 whereas its progeny are green and without wings.* 

 These are mysteries which I leave you entomologists 



turned about on the leaf and moved very slowly, while the female plunged her 

 proboscis into the plant to take food after her exertion. 



" These brief observations confirm the statements of former naturalists, 

 that the Aphides deposit at one period true ova, and at others produce living 

 young ; and they lead us hereafter to inquire more particularly respecting the 

 circumstances which accelerate the one, or retard the other form of develop- 

 ment." George Newport, F.R.S., in ' Transactions of the Linnean Society.' 



* Mr. Walker has obligingly furnished the following detailed descriptions. 



The hop-fly, Aphis Humuli, Schrank, Fauna Boica, ii. 110, 1199. Kal- 

 tenbach, Mon. Pflan. i. 36, 24. A. Pruni Mahaleb, Fonscolombe, Ann. Soc. 

 Ent. Tr. x. 



The migration of some species of Aphides from the plants whereon they 

 pass the winter in the egg state, to different kinds of plants which afford them 

 summer pasture, is one of the most interesting facts in their history. The food 

 of Aphis Humuli is divided between the sloe and the hop, and when the latter 

 is wanting the insect probably lives only on the sloe, or perhaps sometimes on the 

 plum, and is limited to the districts where these trees grow, but their general 

 distribution gives the fly ready access to the hop. 



The Viviparous Wingless Female of the first Generation. This is hatched 

 from the egg in the spring, and swarms throughout May on the sloe, which is 

 also the food of three other species, and there are at least two more kinds that 

 live on the plum. It is grass-green, oval, and very plump, and the whole 

 body is crowded with young ones : the front of the head is slightly convex, but 

 not notched : there is a tubercle like a little horn or joint on the inner base of 

 each antenna ; this process is possessed by many other species, but in a less 

 developed form : the antennae are setaceous, and about half the length of the 

 body ; there is a slight projection on the tip of the first joint ; the fourth joint 

 is much shorter than the third, but more than half its length ; the fifth is a little 

 longer (whereas in most species it is shorter) than the fourth ; the sixth is less 

 than half the length of the fifth ; the seventh is much more slender than the 



