1918-19.] Life-History and Bionomics of Myzus ribis , Linn. 95 
With regard to the winged females, circumstances prevented me from 
taking the average dimensions of a number when living ; and as abdominal 
measurements of spirit specimens are unreliable, the lengths of the antenna, 
forewing, and cornicle alone are given in Table H, as these structures do 
not shrink in alcohol. However, I include the dimensions of a single 
female of this generation, mounted alive in balsam (Table G). The 
decrease in size of the later generation in Table H is perhaps due to 
malnutrition, for during drought in August it was sometimes difficult to 
procure sufficient fresh food. 
It seems, then, that the summer host-plants of M. ribis are certain of the 
Labiatse and other weeds, and that this aphis has been described previously 
during its second cycle as a different species, P. galeopsidis, Kaltenbach. 
The synonymy of this species is rather involved. Davis (6) records P. 
galeopsidis from Polygonum in America. His description closely resembles 
that of the form I have identified as P. galeopsidis, except that he says the 
pupa has a dorsal longitudinal red line, which is even more marked in the 
immature male. But Gillette (13) points out that Davis was actually 
describing Rhopalosiphum hippophces, Koch, and he gives P. galeopsidis 
as a synonym of that species. In America Hippophce is the winter host of 
two allied species — P. hippophces, with clavate cornicles, migrating to 
Polygonum, and M. braggii, Gillette, with cylindrical cornicles, migrating 
to Composite. It is just possible that the latter may be identical with 
M. carthusianus, of which I described an apterous female taken from the 
thistle (15). Gillette believes that Buckton confused these two species 
under the name galeopsidis, figuring the apterous form of braggii and the 
alate form of hippophces. Mordwilko (20) discusses the life-history of 
R. hippophces, and says that Ferrari took the summer migrants from Inula 
graveola. Altogether the synonymy of this group is by no means clear ; but 
it cannot be settled without further knowledge of the bionomics and of the 
sexual forms of these species, both in Europe and America. Until then, 
the best course seems to be to identify the summer migrants of M. ribis 
with the P. galeopsidis of Kaltenbach. 
The following is a list of plants from which the latter species has been 
described by other writers : — 
Galeopsis tetrahit . . . Kaltenbach. 
„ bifida .... 
„ versicolor ... „ 
Lamium album .... „ and Buckton. 
„ purpureum „ „ 
„ amplexicaule . . „ 
