VIVIPAROUS DEVELOPMENT IN NORTH. 49 
frequency. They also account for our inability to locate it in such 
territory during the summer months. 
A careful search was made at different times for grasses that 
were actually serving as summer food plants. The only hope of 
finding such was in well shaded spots along streams, where, from all 
indications, Toxoptera would be sufficiently protected to live and 
reproduce throughout the summer. 
At Piano, Tex., Toxoptera was rapidly disappearing from the 
fields in early June. By June 14 there was only a limited number 
of plants which still supported the remaining few of these aphidids 
and the latter were soon carried away by ants. When confined on 
green food plants and protected from their enemies by a large frame 
covered with thin cheesecloth Toxoptera lived until July 3. After 
this date it was apparently too hot for their existence. Out in the 
open, where young wheat and oats plants were sustained by frequent 
watering, they lived until July 15. After this date they apparently 
could not endure the summer temperature and no more were found. 
Since no reinfestation appeared up to November 30, it was quite 
evident that the aphidids had all perished. 
On June 28 viviparous forms of this species were found rather 
abundantly in a small field of oats at McAlester, Okla. This field 
of a few acres in size was on the east slope of a rocky hill. A natural 
growth of timber surrounded the field and a few trees grew in its 
midst where rocks make cultivation impossible. Green vegetation 
was abundant in shaded places and along the creek one-half mile to 
the east. Conditions of this sort are certainly favorable for Toxoptera 
to live and reproduce throughout the summer as long as they find the 
food plants present. While these spots, favorable to Toxoptera, are 
characteristic of eastern Oklahoma, where, as has been stated, an 
incipient outbreak of the pest actually occurred in 1911, they are 
also found along streams in the central part of that State and in 
northern Texas. As there appears to be no resting or egg stage in 
the South, whenever there is a warm open winter these'' aphidids 
become very abundant and threaten the grain crops of this region. 
IN THE NORTH. 
Farther north, in the vicinity of Lafayette, Ind., viviparous repro- 
duction is confined to the months of April, May, June, July, August, 
September, October, and November. During mild winters, how- 
ever, the species may breed viviparously throughout the year, as the 
senior author found it breeding in the open throughout January, Feb- 
ruary, and March, 1890, notwithstanding the fact that on January 24 
the temperature fell as low as + 3° F.; on February 9, to + 6° F., 
and on March 6 to + 4° F. It appears that a temperature of about 
26675°— Bull. 110—12 4 
