48 
HOP. 
Hop Aphis side by side up to this point, we find them starting at the 
same time in spring respectively on their several plants, continuing 
similarly to increase ; and similarly about the end of May to gain the 
winged state ; and up to this date, by constant microscopic examina¬ 
tion, I did not find any difference in the frontal development of the 
young lice of the kinds under consideration when first produced, nor 
in that of the winged females. 
The accompanying figures, drawn from life, show the similarity. 
1, 2, Hop Aphis; 3, 4, Damson-Hop Aphis. 
During June, that is, when Fly is considered (both by many Hop- 
growers and also entomologists who have studied the point) to be 
leaving the Damsons, and is certainly appearing on the Hops, speci¬ 
mens were still sent me; and on the 26th of June, when a corre¬ 
spondent especially attending to this subject reported that he could 
find none left on Damson and few on Sloe, I considered his observa¬ 
tions confirmed, and likewise the theory of migration, by the fact that 
all the specimens he sent me were winged pupae—that is, had embryo 
wings—which showed they would soon turn to the winged state, i. e., 
to Fly. 
I think this is very important, for the fact of all that remained on 
the sprays sent me being winged or forming wings, joined to previous 
departures, points to the absentees having flown somewhere. They had 
not died, or they would have been found on the bushes; they have 
not, as far as I am aware, ever been found infesting any other food- 
plants than Hop and Plum of various kinds ; and with regard to these 
food-plants, we find the Aphides, as just mentioned, forming wings, 
and leaving the one set of plants just when attack is appearing on the 
other. Regarding migration, see ‘Brit. Aphides,’ vol. i., p. 74. 
That such migration does take place in Aphis life we have direct 
testimony. M. Jules Lichtenstein indeed states that “in the greatest 
part of plant lice the second form is winged, and flies away from the 
