Feb. 16,1924 Effect of Light Exposure on Migration in Aphids 517 
upon hatching, the young were placed on a small apple seedling in the 
dark chamber. The second generation appeared on April 13, entirely 
wingless, contrary to the habits of this species in the North. The first 
winged forms were observed on April 24. In spite of the fact that this 
species was kept on a short day until June 1, the sexes had not made 
their appearance. Several times they had increased to such an extent 
as to kill the plants. This necessitated the saving of a few stragglers 
that managed to live and the placing of them on a new plant which 
had not been exposed to a short day. The process of changing plants 
continued three times, which may account for the nonappearance of 
the sexes. The same was true with Aphis spiroecola. 
Chaitopborus negundinis Thom.—The boxelder aphis is rather peculiar 
in that it has a resting stage, or dimorph, during the summer months. 
Winged forms are produced that fly to other boxelder ( Acer negundo) 
trees, but as the summer approaches the dimorphs appear as the normal 
individuals disappear. With the approach of autumn the dimorphs 
become active and give birth to those forms which produce the sexes. 
Experiments were undertaken to determine whether the dimorph is 
also a product of long days. Plants $rere kept under a long day of 15 
hours, starting March 30, 1923. The eggs hatched out of doors on March 
1. The first dimorphs were found out of doors on May 3, about the same 
time that they appeared in the long-day experiment. In a few weeks' 
time the aphids killed the plant kept in the dark chamber, so that the 
experiment had to be discontinued. 
On May 20, 1923, a plant bearing dimorphs was placed in a dark room, 
and within a day the dimorphs started to move around, indicating their 
sensitiveness to light. Their reactions to a long and a short day, however, 
remain to be proved. 
Aphid on Heuchera americana .—G. G. Ainslie, of the Bureau of 
Entomology, United States Department of Agriculture, called the 
writer's attention to a Macrosiphumlike aphid on Heuchera americana 
that produced the sex forms in April and deposited eggs in May, a pro¬ 
cedure quite out of the ordinary. Here was a case so different that it 
was thought worth while to note the effect of light exposure on this 
species. Accordingly plants were placed in a dark chamber, as well 
as under an artificial long day, on March 27, when the stem-mothers 
were found producing young. Males and females made their appear¬ 
ance in, both cases the first week in May, indicating that the sequence 
of generations has been determined from the egg stage onward. 
INFLUENCE OF THE LONG DAY ON THE INHIBITION OF THE SEX 
FORMS. 
From the experiments with Aphis forbesi , it is apparent that the pro¬ 
duction of the true sexes appears to be governed by the short days, such 
as are present during the fall of the year. If such is the case, it should 
be possible to keep the sexes from making their appearance by exposing 
the plants to a long day. Beginning with September 4, strawberry 
plants bearing Aphis forbesi were given 15 hours of daily light exposure 
by means of a 60-watt Edison Mazda light that hung about 2 feet from 
the plants. The plants were kept lighted out of doors, so as to keep 
the temperature factor constant. The use of the light did not alter the 
temperature near the strawberry plants. At the same time a control 
plant was placed inside of the laboratory window. 
