1918-19.] Life-History and Bionomics of Myzus ribis, Linn. 81 
Table A. 
The dimensions of two fundatrices from red blister and green leaf respectively. 
Red Blister Form. 
Green Leaf Form. 
Absolute 
Dimensions. 
Dimensions 
expressed as 
per cent, of 
Breadth of 
Head between 
Eyes. 
Absolute 
Dimensions. 
Dimensions 
expressed as 
per cent, of 
Breadth of 
Head between 
Eyes. 
mm. 
mm. 
Breadth of head between eyes . 
•29 
100 
•28 
100 
Length of body 
2*30 
790 
2-77 
989 
Greatest breadth of abdomen 
T38 
475 
•98 
350 
Breadth between cornicles 
•70 
241 
•57 
203 
Length of cornicles . 
•40 
130 
•33 
117 
Total length of antenna 
1-85 
637 
1-40 
500 
Femur (metathoracic leg) . 
*65 
224 
•50 
178 
Tibia (metathoracic leg) . 
•90 
310 
•90 
32 L 
the form from the green leaf is actually, as well as proportionately, longer 
and narrower than that from the blistered leaves — a difference appreciable 
even to the naked eye. 
Table B. 
The average dimensions of twelve apterous females from red blister compared with 
those of twelve similar forms from green leaf. 
Red Blister Form. 
Green Leaf Form. 
Average 
Absolute 
Dimensions. 
Dimensions 
expressed as 
per cent, of 
Width of Head 
between Eyes. 
Average 
Absolute 
Dimensions. 
Dimensions 
expressed, as 
per cent, of 
Width of Head 
between Eyes. 
Width of head between eyes 
mm. 
•31 
100 
mm. 
•31 
100 
Length of body 
2-01 
648 
2T8 
700 
Greatest breadth of abdomen 
•95 
300 
•83 
267 
Breadth between cornicles 
•67 
200 
•50 
161 
Total length of antenna 
2-36 
671 
237 
764 
Length of cornicles . 
•30 
96 
•31 
100 
Length of femur 
•56 
180 
•57 
183 
Length of tibia 
1*31 
422 
1-41 
454 
This disparity is maintained in the succeeding apterous generations 
(Table B). Henceforth, for the sake of brevity, the two forms will be 
distinguished as “ red blister ” and “ green leaf ” respectively. It will 
be seen that the most striking difference again occurs in the length and 
breadth of the abdomen. The dimensions of this part in insects are 
VOL. xxxix. 6 
