520 
Journal of Agricultural Research voi. xxvn. no. r 
in either case; but not all became winged. A few remained on the 
snowball and produced a third and a fourth generation, the majority 
of which were winged. The last individual died May 26 on the snowball. 
It is of interest to note that the young of the third generation have a 
rosy tinge, and are unable for the most part to thrive on the snowball. 
Eriosoma lanigera Hausman.—On February 5, a seedling infested with 
the apple woolly aphis was brought into the laboratory and placed in 
water. Winged forms were observed on April 2, and upon dissection 
yielded the true beakless sexes. The short days of the winter and spring 
months no doubt stimulated the production of the sexuparae. The 
winged forms were present on the bark, so that it appears that the stimu¬ 
lating factor is present in the sap. 
Normally the fall migrants appear very sparingly during September 
and October, but in the laboratory they appeared in immense numbers. 
THE PRODUCTION OF EGGS IN THE SUMMER 
Although the great majority of the aphids lay their eggs in the fall, 
several species are now known to produce the sexes and eggs in summer, 
Gillette (9) finds that with Aphis saliceti the males and females make 
their appearance in June; while Doctor Patch, in a letter to the writer, 
states that in Maine mature oviparous females of Macrosiphum pur pur- 
ascens were collected in June and July. In Tennessee there is an aphid 
on Heuchera americana that produces its sexes in May; and what is 
probably the Georgia ulmi of Wilson has recently been taken which 
deposits its sexes in May and June on a species Ulmus that is either alata 
pr racemosa. As far as can be determined, the sexes of the latter two* 
species are the third generation, the sequence of which appears to be 
predetermined, because of the small number of generations, and is not 
affected by the length of day. 
That the length of day is not the only factor influencing the production 
of eggs is indicated by the fact that a few tropical aphids are known to 
produce eggs. Baker, in a letter to Doctor Patch, states that “ in tropical 
countries where there is a distinct rainy and dry season and where the 
trees leaf twice a year, the insects seem to accommodate themselves to 
this condition. ,> Das (4), working at Lahore, India, found that the aphids 
there have a definite migration and produce sexual eggs, which are 
normally deposited during January and February; while a few species,, 
such as Brachyunguis harmalae , deposit eggs also in May that hatch in 
September in order to tide the insects over the dry season. Sexual 
forms have not been observed by Mason (14) in Florida, which is in 
about the same latitude as India. Similarly in Java, Van der Goot (10) 
states that the sexual eggs have never been found. 
CONCLUSION 
Sex production and migration in the Aphididae can be controlled 
experimentally by subjecting the hosts to definite amounts of daily light 
exposure and they do not appear to depend on temperature, at least in 
the Temperate Zones. The question naturally presents itself, whether 
there is a direct action of light on the insect which stimulates egg pro¬ 
duction, or whether the chemical change in the plant subjected to a short 
day, is the stimulating factor. Observations made in the laboratory and 
the fact that root-feeding aphids away from direct action of the light 
