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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
about 15 young and in 1917 we found stem-mothers on April 14 with 
colonies of young. 
The third generation probably makes its appearance a little after 
the middle of April or possibly even sooner. 
In 1915 we observed the mature winged individuals of this genera¬ 
tion on May 5. In 1916 we observed a colony on May 12 in which 
25-50 per cent of the individuals were winged. In 1917 we found 
the first winged individuals as early as April 27. Under optimum 
conditions winged individuals from elm might be found from this 
time on until nearly the last of July. We have found them as late as 
July 21. Parasites usually cut this generation short so that under 
normal conditions it is difficult to find the species on elm after the 
first week of June. 
We have not worked out the number of generations of aerial apterous 
viviparise occurring on Crataegus and apple. Fall migrants make 
their first appearance with us by the middle of September and in 
favorable seasons may be found as late as the middle of November. 
There would thus be a period of five months between the appearance 
of the first spring migrants and the first fall migrants and a period of 
four months between the last spring migrants and the first fall mi¬ 
grants. If the aerial viviparise mature in the same time that the root 
forms matjire (15-25 days), there would certainly be time for the 
development of more than two generations as recorded for Maine by 
Miss Patch 1 and for Vienna, Va., by A. C. Baker. 2 
On the roots of apple the apterous viviparise become active by the 
first of March and continue active until along in November. From 
the data which we have, this would make it possible for six to twelve 
generations to develop during the course of a year. 
Experiments with Spring Migrants 
With a view of determining whether the young of individual 
migrants would establish on either elm, Cratsegus or apple, a series 
of experiments was begun in which some of the young of each migrant 
tested was placed on each of the hosts. A safer and more satisfactory 
method of distributing the young consisted in transferring the migrant 
from host to host and permitting her to deposit young on each. We 
found that once a migrant begins to deposit young she usually con¬ 
tinues to deposit them in rapid succession until exhausted. 
In no case did the offspring of the migrants find elm congenial. 
In view of the fact that many elms are immune to the insect and that 
1 Maine Agricultural Experiment Station Buis. 220 (1913) and 256 (1916). 
2 Report No. 101, U. S. Department of Agriculture, Office of the Secretary, 1915. 
