94 
Proceedings of the Royal Society of Edinburgh. [Sess. 
or four smaller spots at the sides ; and galeopsidis with a threefold spot 
in front of the cornicles, and two separate bands anterior to it. An 
examination of the twelve examples of each form measured in Table C 
shows that lateral spots may occur in galeopsidis , and bands on the anterior 
segments of the abdomen of ribis. The latter vary much, and in the red 
blister form often appear only as a narrow streak behind the metathorax, 
but in some specimens from green leaves they are nearly as pronounced 
c d 
Fig. 7. — Diagrams of the abdominal pattern of 
(a) Myzus ribis, winged 9 from red blister. 
(b) ,, ,, ,, ,, green leaf. 
(c) ,, ,, ,, of the first generation after transference to Galeopsis 
tetrahit. 
( d ) Phorodon galeopsidis, Kalt., from Galeopsis tetrahit. 
as in galeopsidis. In fact, when females from red-blistered currants and 
Galeopsis are compared, it would be a pardonable mistake to refer them to 
different species. It is only when a series is examined that the differences 
are found to be linked together completely by a chain of intermediate 
forms (fig. 7). 
The first females of M. ribis transferred to Galeopsis did not show any 
appreciable effects of the change, but their progeny (A. I, 8 from the funda- 
trix on currant) were remarkable for an increase of size in both winged 
and wingless forms. The latter, breeding females and nymphs, were 
indistinguishable from similar examples of P. galeopsidis. 
