Oct. IS, 1917 
Life History of Macrosiphum IUinoisensis 
85 
SPRING MIGRANT 
The spring migrants begin to appear in the second generation, although 
their number is not abundant until the third generation, and their pro¬ 
duction then gradually decreases for several generations. It is thus evi¬ 
dent that the spring migration extends over a considerable period. It is 
at its height during the first week in May. 
The spring migrants fly to wild grapes and to the grapes in vineyards. 
In Virginia, where the writer conducted his experiments, wild grapes 
often grew very close to the viburnums, and in some cases they even 
climbed over the viburnum bushes. In such cases migrants took grapes 
close at hand, although the vines in the viburnum bushes were not 
thickly infested. The migrants, however, are capable of rather extended 
flight, having been noted on grapes about a mile distant from the nearest 
viburnum bushes. It would appear that the first migrants developed 
take to the wild grapes in the vicinity of the viburnums, for the first 
migrant discovered upon the cultivated grapes was taken on April 28. 
This is considerably later than their first appearance. By May 1 this 
specimen had produced many young upon the grape, whereas the bulk 
of the migrants had not yet made their appearance. 
Fourth instar (pupa).— General color reddish brown, the wing pads, legs, and 
cornicles dark; eyes black. Antennae yellowish brown with the distal segments dusky. 
Antennae of six segments; segment III, 0.304 mm.; IV, 0.24 mm.; V, 0.208 mm.; VI, 
0.096 plus 0.32 mm.; cornicles tapering, distinctly imbricated, and 0.336 mm. long. 
Length from vertex to tip of cauda, 1.36 mm. 
Fifth instar (adult).— Color a deep reddish brown, appendages and cornicles 
darker, the tibiae with a lighter median area; eyes black; wings with dusky veins and 
stigma. The antennae are distinctly imbricated on all segments excepting I and II. 
Segment III armed with from 6 to 14 sensoria arranged in an uneven row on the basal 
three-fourths of the segment. In some cases the sensoria cover the entire segment. 
They are uneven in size, some being fairly large while others are quite small. The 
cornicles are somewhat tapering, very distinctly imbricated, and with distal extremity 
not distinctly flanged. Cauda about half the length of the cornicles. Length of 
fore wing, 2.4 mm.; length from vertex to tip of cauda, 1.328 mm. The relative 
lengths of the antennal segments and cornicles are given in Table I. 
Table) I. —Lengths (in millimeters ) of antennal segments and cornicles of spring 
migrant of Macrosiphum illinoisensis , with host , and number of sensoria on antennal 
segment III 
Date. 
Host. 
Segment 
III. 
Number 
of sen¬ 
soria on 
segment 
III. 
Segment 
IV. 
Segment 
V. 
Segment VI. 
Cor¬ 
nicles. 
Apr. 28 
Viburnum. 
O. 432 
13 
O- 336 
0. 272 
0. 096+0. 32 
O. 368 
Do 
... do. 
. 416 
7 
. 352 
• 304 
. II2*+ . 32 
• 4 
Do 
...do. 
. 368 
# 
7 
. 32 
. 256 
. 112 + . 304 
• 35 2 
Do 
..,do. 
• O 
.288 
7 
• 3 2 
. 272 
. 112 + . 336 
• 35 2 
May 1 
Grape. 
■ 35 2 
t 
8 
.304 
. 272 
. 096+ . 352 
•336 
May 4 
■ 336 
10 
.288 
.24 
. 096+ . 336 
. 416 
May s 
• 3 8 4 
11 
• 33<5 
. 272 
. 112+ . 288 
. 368 
