69 
Buekton (British Aphides, vol. 1, p. 70) has the following to say with 
regard to the effect of weather on this and other species of Aphides : 
Violent changes of*temperature seem much to check the multiplication of the 
Aphides. <A cold rain, or the outburst of a thunder storm, will often cause the almost 
entire extermination of swarms, and wash them, never to return, from their native 
plants. Nevertheless, the close and hot atmosphere before a thunder storm seems to 
to be peculiarly suited to their propagation. At such times the winged forms occur 
in great numbers and take flight on the gentle winds, which transport them many 
miles to other feeding grounds, to become the foundresses of other colonies. 
The effect of the parasites on the Grain Louse was simply astonishing, 
while their numbers were myriads. Going to the fields of recently har- 
vested grain, if one stood in a position to bring the newly made shocks 
between himself and the setting sun, he could clearly observe the 
swarms of minute Hymenopters arising therefrom and flying away. Be- 
sides, the stubble-fields were overrun with lady beetles and their 
larvee. 
Nevertheless, there are good grounds for the belief that the heavy 
showers during the latter part of June and early July, in the central 
and northern portions of Indiana, washed many young from the heads 
of the grain and destroyed them. Besides, either the severe thunder 
and lightning which accompanied these storms or the rapidly matur- 
ing grain, or both, perhaps, caused the winged adults to betake them- 
selves to the oat-fields, where they would probably have caused further 
damage had not their relentless foes, the Hymenopters, pursued them 
and continued their work of destruction. 
It was a common sight early in July, in northern Indiana, to see 
adults of the grain-lice attached singly to heads of oats, sometimes with 
a few young clustered about them, assuming the form and color so in- 
dicative of parasitism. In southern Indiana, late in June, the same 
thing was observed on oats, and parasitized adults were also abundant 
on the heads of blue-grass, even long distances from grain fields. 
In summing up the matter, it may be safely said that wet weather 
will not, of itself, prevent an outbreak of the grain Aphis, or dispel it 
after under full headway. It must be borne in mind, however, that cool 
wet weather, during May and June, will enable grain plants to sustain 
greater drafts on their vitality than will very dry and hot weather. It 
is also probably true that a cool temperature during spring and early 
summer is either directly or indirectly favorable to the development of 
the grain Aphis. 
Regarding the life history of the species under consideration we have 
never found them in the fields at an earlier date than April 27. From 
this time we have an unbroken record of their occurrence up to July 9, 
when there is a break in their continuity of appearance until Septem- 
ber 1, when full grown apterous females were found on leaves of early 
sown wheat. From this latter date we again have an unbroken record 
up to December 30. We have also observed the sexes pairing on No- 
vember 11 and December 5. 
