‘+ 
SUMMER NUMBER 2 
_ adults reared a family the majority of which were winged. From 
. 
each of these families some winged and apterous individuals were 
selected and the work continued for three generations. These 
results show that there is a distinct alternation of winged and ap- 
terous forms of Lachnus pini. In the case of four lines run for 
three generations there was in every case a majority of apterous 
young from winged parents and of winged young from apterous 
parents, and in some cases it was 100 per cent. This work was 
- then continued by rearing the aphids on cut stems in the labora- 
tory in both water and salt solution with checks on a growing 
tree. Here with one exception the same phenomenon was ob- 
served. In all, twelve winged adults from whom families were 
reared and counts of the offspring made produced an average of 
72.1% apterous young; and in the case of six apterous females 
there was an average of 93.1% winged young. In several other 
cases of each form a majority was observed to exhibit this alter- 
nation of generations but no counts were made. As the results 
show, the cut stems had no influence in changing this proportion. 
So we conclude that even if the aphids are reared on unhealthy 
or dying stems the effect will not counteract the alternation of 
winged and apterous forms. 
In practically all cases the first few young from a winged 
parent were apterous and vice versa. This may account for the 
_ fact that the percentage is perfect in some cases where the adult 
1 
lived only long enough to raise a few young. The percentage of 
winged young from apterous parents is higher than that of 
apterous young from winged parents. The alternation of winged 
and apterous forms accounts for the fact that winged forms were 
observed in the field only at certain intervals. A winged adult 
might fly to a new tree and start a colony which would be all 
apterous. These would then produce families which would be 
largely winged. However, nearly a month would be consumed 
before the winged ones would become adult, during which time 
no winged forms would be seen, and then within a few days many 
winged ones would appear. This was observed on several dif- 
ferent occasions. 
SUMMARY 
We can draw the general conclusion from all of these experi- 
ments that external conditions and environmental changes do not 
effect the production of winged forms of aphids, at least not in the 
first generation. This was proven by confining aphids on injured 
and dying pine trees; by raising aphids on cabbage plants show- 
