HOP APHIS. 
83 
leceived specimens of this caterpillar from Kilmacurragh, Rathdrum, 
Ireland, which were forwarded on twigs of this tree, with a note that 
it was the first time the sender had seen this kind on Evergreen Oak. 
The caterpillars were remarkably fine specimens, and were feeding 
voraciously on the Evergreen Oak sent with them. 
HOP. 
Hop Aphis. Phorodon humuli, Schrank; Aphis humuli, Schrank. 
During the past year the subject of the migration of Hop Aphis 
from Plum to Hop in the early part of the year, and from Hop to Plum 
in the late part of the season, has been so thoroughly investigated as 
to make it appear fully proved that this regular migration to and fro 
does take place. It has long been considered by many Hop growers 
that migration occurs, and it has also been definitely stated to be the 
case by observers competent to distinguish the precise kind. 
So long ago as 1854, Prof. C. L. Koch recorded that he found Hop 
Aphis on Plum and Sloe ; and it is worth notice that he mentions the 
great numbers in which it was found on these trees or bushes in the 
latter part of May, and that he gives the description of this Hop Aphis 
in its various stages (that is female, young, &c.) from what he saw on 
the Plum and Sloe; and after details of these, then he adds . . . “ In 
the month of June this kind of Aphis quits the leaves of the Sloe ” (or 
wild Plum) “ and then betakes itself to the wild and cultivated Hop, 
where it settles on the under side of the leaves, sometimes in 
immense numbers.”* This and other observations, unnecessary to 
repeat here, show spring migration on the continent of Europe. 
In this country, after long examination of the Aphis in the 
conditions commonly called Ely and Louse (that is winged and 
wingless), and including young, more advanced young, and females, I 
could not find that any difference in form of the characteristic points 
of structure (by which the Hop Aphis is known) were to be noticed 
between the kind technically known as the Phorodon , which was found 
on Hop, and that found on various kinds of Plum.f 
The figures show the almost exact similarity of shape in the 
frontal tubercles, and of the swollen or toothed lowest joints of the 
horns of the Hop and the Damson Hop Aphis, that is Phorodon , found 
* ‘ Die Pfianzen Lause (Aphiden),’ von L. C. Koch, pp. 114—116. 
f See Eighth Eeport on ‘Injurious Insects’ (Hop Aphis), pp. 43—56, with 
figures to show similarity of form in forehead and base of antennae between the 
specimens taken respectively from Hop and Plum. 
G 2 
