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, 
wdiereas 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. PJlan. 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 Generatioii. — 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 
