1918-19.] Life-History and Bionomics of Myzus ribis , Linn. 91 
markings ‘'extend across the abdomen in transverse bands instead of a 
solid patch.” 
M. dispar was first described by Miss Patch (23) from specimens 
taken together with M. ribis on gooseberry and currant in America. 
Dobrovliansky (9) also records it from black currant in Russia. The 
apterous form is green, and the alate form is very pale green, with three 
vivid longitudinal lines and a few blackish transverse markings on the 
caudal half of the abdomen. The pupa is pale green, and when nearly 
ready for the final moult, it has the thoracic lobes pellucid brown like 
the thorax of the winged female. I have already remarked that the 
colour of M. ribis varies with the character of the food, and therefore 
specific distinctions cannot be based on the colour of the wingless female ; 
but the abdominal markings of the winged form do not correspond with 
those of M. ribis , nor does the dark thorax of the nymph. But for these 
differences, I should have been inclined to think that M. dispar was 
nothing but the green leaf form of M. ribis, for the author goes on to 
make a distinction between the antennal joints of the two species, which 
is precisely the difference which I have shown to exist between the two 
forms of M. ribis. She says : “ In ribis, the terminal sensorium in Joint 
V and the sensorium at the base of the spur in Joint VI approximate the 
articulation between V and VI much more closely than is the case with 
dispar. Joint III is more slender in ribis, and the sensoria are proportion- 
ately larger. . . . The cornicles of dispar are relatively shorter and less 
slender than those of ribis.” 
It was this observation of Patch which led me to take the measure- 
ments between the permanent sensoria (fig. 3). Before, I had based the 
distinction between the green leaf and red blister forms only on the 
presence or absence of supplementary sensoria on Joint V. Patch does 
not mention the latter feature in the text, but she gives two excellent 
figures, in which M. ribis is shown with supplementary sensoria on this 
joint, and M. dispar with none at all. With regard to the cornicles — 
the cornicles of the green leaf form of ribis are proportionately shorter 
than those from the red blister. 
In spite of the difference in colouring, which possibly may be accounted 
for by another climate, I incline to the view that M. dispar may prove 
to be identical with the green leaf form of M. ribis. 
The Life-Cycle. 
The life-cycle of M. ribis has been treated by several writers, notably 
by Kaltenbach, Koch, and Flogel in Germany, by Buckton and Theobald 
