121 
This plant-louse (Fig. 14) varies in color from pale yellowish 
to blackish green. Its life history and insect enemies are very 
similar to those of many other plant-lice, such as the one which has 
already been discussed as a cabbage insect (page iii). Briefly, the 
melon aphis appears on cucumber and melon plants early in the 
Fig. 14. Melon Aphis, Aphis gossypii: a, winged female; aa. 
enlarged antenna of same ; ab, dark female, side view ; b, 
young nymph or larva ; c, last stage of nymph ; 
d, wingless female, — all greatly enlarged. 
season, and increases rapidly in numbers during the summer unless 
checked by its insect enemies or by unfavorable weather. It is 
still doubtful whether it ever produces eggs to carry the species over 
winter, but it is known that viviparous females — the form found 
thruout the summer — may hibernate in some parts of Illinois. 
Remedial I\Ieasitres. — The measures recommended for the con- 
trol of the cabbage-louse (pages 112-113) may be used against the 
melon aphis, and of these, fumigation with carbon bisulfid is 
doubtless the most efticient. 
Owing to the large number of its food plants, clean culture is 
especially important in dealing with the melon aphis, particularly 
the cutting and burning of weeds and old vines; and fall plowing 
is also advisable. 
In greenhouses, fumigation with hydrocyanic acid gas is doubt- 
less the best treatment for this insect. The procedure is described 
on pages 156-158. 
The Greenhouse White-fly 
Aleyrodes vaporarioriun Westwood 
One of the most troublesome and "destructive insects with which 
the greenhouse vegetable-gardener must deal is the white-fly. This 
little pest attacks cucumbers, tomatoes, peppers, and lettuce under 
glass, and a considerable variety of flowering and ornamental 
plants. 
The winged adult (Fig. 16) is about .06 (one seventeenth) of 
an inch in length, and looks as if dusted with flour. The minute 
