28 THE FLORIDA ENTOMOLOGIST 
grow. A week later another small colony, (N), taken from the 
same place as the others, was placed on another limb. Colony M 
had a start on colony N and should be more numerous and show 
any effects of crowding sooner than N. The results show no 
difference. In fact colony M produced winged forms before N 
was even started and while there were only a few aphids there, 
and continued to produce them as long as the colony lived there. 
Therefore crowding as a probable cause of wing production was 
given up. 
Effect on Myzus persicae of Injuring Cabbage Plants. This 
experiment was tried in the greenhouse insectary and its object 
was to see if unfavorable conditions of growth for a cabbage 
plant will cause aphids of the species Myzus persicae growing 
on it to produce wings and seek a new plant. Twelve potted cab- 
bage plants were placed on the bench and covered with lantern 
globes, and divided into three groups. The first four had a cord 
tied lightly around the stem which would shut off the flow of sap 
to some extent. The next four were given no water and allowed 
to dry up. The third four were kept in a normal condition and 
used as checks. Each of the plants had a number of aphids placed 
on it and left for two weeks, the results being recorded each day 
or two. As the table shows, winged forms were produced on all 
of the plants without discrimination. In fact the total number 
on the four plants of each group is about the same. The results, 
therefore, do not argue in favor of the unhealthy condition of 
plants causing wings. 
Mature Aphids. Eight adult apterous Lachnus pini, which 
had already produced some young, were placed on a cut stem 
which had already become partially dried out. All died in less 
than a week and produced no wings. It is hardly reasonable to 
believe that an adult could develop wings. 
EFFECT ON APHIDS OF ADDING CHEMICAL SOLUTIONS TO THE 
Foop OF THE HOST 
Some experiments were next run to determine if changing 
the sap of the host plant by adding chemical solutions to its food 
would cause aphids on it to produce wings in order to seek a 
new host. Some of these chemicals would undoubtedly be taken 
up by the plant and consequently added to the dietary of the 
aphids. First, some cabbage plants which were infested with 
Myzus persicae were watered with solutions of magnesium sul- 
phate of varying strengths. Small pots were filled with clean 
