84 
Proceedings of the Royal Society of Edinburgh. [Sess. 
Table C. 
Dimensions of winged females of Myzus ribis from red blister and green leaf, of Ribes 
rubrum from Galeopsis tetrahit , and of Aphis galeopsidis of Kaltenbach. 
Average of twelve individuals in eacb case. 
Red Blister 
Form. 
I 
Green Leaf 
Form. 
Fourth Genera- 
tion after 
Transference to 
Galeopsis tetrahit. 
Aphis galeopsidis 
Kalt. 
Average 
Absolute 
Dimen- 
sions. 
Dimen- 
sions ex- 
pressed 
as per 
cent, of 
Length 
of Fore- 
wing. 
Average 
Absolute 
Dimen- 
sions. 
Dimen- 
sions ex- 
pressed 
as per 
cent, of 
Length 
of Fore- 
wing. 
Average 
Absolute 
Dimen- 
sions. 
Dimen- 
sions ex- 
pressed 
as per 
cent, of 
Length 
of Fore- 
wing. 
Average 
Absolute 
Dimen- 
sions. 
Dimen- 
sions ex- 
pressed 
as per 
cent, of 
Length 
of Fore- 
wing. 
Length of forewing 
mm. 
2-31 
100 
mm. 
2-61 
100 
mm. 
3-06 
100 
mm. 
327 
100 
Length of body 
1-59 
68 
1-84 
70 
2-10 
68 
2*35 
71 
Greatest breadth of 
•52 
22 
•59 
22 
•68 
22 
•71 
21 
abdomen. 
Breadth between 
•32 
14 
•30 
11 
•36 
11 
•37 
11 
cornicles. 
Total length of 
1-99 
86 
1*87 
71 
2-87 
93 
3-03 
92 
antenna. 
Length of cornicles 
•23 
10 
T9 
7 
•20 
6 
•22 
6 
but these are always small and never tuberculate, as in the red blister 
forms. Fig. 2 shows the range of variation in this feature in seventeen 
sister females — granddaughters of a female with the typical form of 
open-leaf joint. Five of these had no sensoria on Joint Y of either 
antenna. Of the remainder — 
4 had 4 sensoria 
4 „ 3 
3 „ 2 „ 
1 „ 1 sensor ium. 
But of these twelve females, only three had additional sensoria on each 
antenna. In the rest, the other antenna was of the typical green 
leaf type. 
Besides the absence of sensoria on Joint Y, the green-leaf form differs 
from that from the red blister in the smaller size of the sensoria on Joint 
III and Joint IY. This variation in the antenna is not alluded to by 
the older writers on Myzus ribis . Buckton does not mention it, and 
