Feb. 21, 1916 
Green Apple Aphis 
981 
It will be noticed that a comparison of the figures for the entire season 
gives the winged form a larger average reproduction per insect than the 
wingless. This is because no winged individuals occurred during the 
third period when the number of young produced was very low. Elimi¬ 
nating this factor we find that for the first two periods the average for 
wingless insects was 43 + young, while for the winged aphides it was 
only 37.7. Unweighted averages have been used here, since it is desired 
to compare merely the production by the two forms under similar con¬ 
ditions, and the fact that wingless insects were so abundant during the 
second, or poorer, period would make the use of weighted averages unfair. 
PRODUCTION OP SEXES 
Both wingless and winged viviparous females may, in addition to pro¬ 
ducing viviparous females, produce the sexes. However, the wingless 
individuals are much more commonly sexuparous than the winged in¬ 
sects, since sexes were reared from only three individuals of the latter 
form. 
DIMORPHIC REPRODUCTION 
No exact data are available on which to base statements as to the prev¬ 
alence of dimorphic reproduction—the production of two different forms 
by one mother. Nevertheless, enough data are at hand to show that it 
is of very frequent occurrence during the summer and may even be the 
rule. In several cases wingless, winged, and intermediate mothers pro¬ 
duced both wingless and winged offspring. In many cases the first 
young produced were all wingless, while later progeny were winged; but 
this was not always true, since the very last young were sometimes 
wingless. 
In a very few cases wingless mothers produced both viviparous and 
oviparous females, and in one or two instances both males and ovipa¬ 
rous females. Again, in a few cases it was possible to determine that one 
mother produced both oviparous females and males, while in one instance 
a single viviparous insect produced viviparous females, oviparous females, 
an.d males. The production of oviparous females and males by the 
same mother is probably of quite common occurrence, but the dimorphic 
reproduction, including both agamic and sexual forms, appears to be 
rare. In the vast majority of cases one mother will produce only vivip¬ 
arous females or the sexes. It is of interest to note that in most of 
the cases recorded the agamic young were produced first and the sexes 
were the last forms produced by the mother. 
OVERLAPPING GENERATIONS 
Since the writers did not select the first and last young from each 
mother, they did not obtain exact data on the duration of each generation. 
However, using the average length of life of the various generations in 
