Oct. IS, 1917 
Life History of Macrosiphum Illinoisensis 
87 
practically like those of winged form, having a row of sensoria on segment III. Meas¬ 
urements of antennal segments average about as follows: Segment III, 0.432 mm. 
with about 9 sensoria; IV,0.352 mm.; V, 0.256 mm.; VI, 0.096 plus 0.432 mm. Comi* 
cles 0.495 mm M length from vertex to tip of cauda, 1.92 mm. 
SUMMER WINGED VIVIPAROUS FEMALE 
Winged forms (PL 9, A, D) are produced in every generation from the 
second onward, but fewer winged line generations occur than wingless 
line generations. The winged forms show the same variations as the 
wingless ones, some specimens being large and light brown, while others 
are very small and black. The small dark forms occur during the hottest 
months of summer, while the large paler forms are usually met earlier 
in the spring. The winged forms produce an average of six young a day. 
Fifth instar (adult) (PI. 9, A).—General color dark brown. The color, however, 
varies greatly, some specimens being a deep black and others being almost of a yellow¬ 
ish color. Thorax black; eyes, hind legs, and cornicles black, middle and fore legs 
with yellowish bands around the segments and with the areas about the joints black. 
Wings hyalin, the veins and stigma dusky. Antennae distinctly imbricated and with 
from 7 to 13 sensoria on segment III. Cornicles tapering, strongly imbricated, slightly 
curved and held outward from the body. Length of forewing, 2.72 mm.; length from 
vertex to tip of cauda, 1.44 mm. Relative lengths of antennal segments and cornicles 
given in Table III. 
TablB III.— Lengths {in millimeters) of antennal segments and cornicles of summer 
winged vivipara of Macrosiphum illinoisensis , with the number of sensoria on antennal 
segment III 
Generation. 
Segment 
III. 
Number 
of sensoria 
on segment 
III. 
Segment 
IV. 
Segment 
V. 
Segment VI. 
Cornicles. 
Third . 
0. 416 
II 
0.32 
O. 304 
O. 144 + 0 - 384 
0.4 
Sixth. 
•4 
8 
• 336 
. 272 
. 096+ . 32 
-4 
Eighth. 
•352 
13 
■ 336 
. 24 
• 096+ . 336 
• 384 
Do. 
. 272 
7 
.24 
. 208 
. 08 + . 352 
•32 
FALL MIGRANT 
The fall migrants are produced upon the grapes during the early part 
of October and are found upon the viburnum depositing young oviparous 
females during the second week in that month. They are somewhat 
different in general appearance from the summer forms, being lighter and 
smaller. 
Fifth Instar (adult). —General color reddish brown, rather pale as compared 
with the summer winged form. Thorax and sternal plate black; antennae dusky; 
cornicles and hind legs black; anterior and middle legs yellowish brown, dusky at the 
joints; wings hyalin with dusky veins and stigma. Antennae (PL 8, B) strongly 
imbricated, segments III, IV, and V with sensoria as indicated in Table III. Cornicles 
tapering, distinctly imbricated, and not enlarged on the distal tip. Cauda and anal 
plate black. Length of forewing, 2.7 mm.; length from vertex to tip of cauda, 1.44 
mm.; measurements of antennal segments and cornicles given in Table IV. 
