Fm. fo 7. A dead potato aphis that has contained a parasite, which when adult escaped through the door cut in the back of the aphis
home. The guest that so ravishes its protector is the grub of a small wasp- like insect (Fig. mS) with a long, sharp ovipositor by means of which it thrusts an egg into the body of a living aphid
Fro. mS. .4phMius, a coin- mon small wasplike parasite of aphids
on almost any plant, you will most likely note here and there a much swollen aphid of a brown- ish color. Closer examination reveals that such individuals are dead, and man)' of them have a large round hole in the back, perhaps with a lid standing up from one edge like a trap door (Fig. ?o7). These aphids have not died natural deaths; each has been made the involuntary host of another insect that con- verted its body into a temporary
Fro. ??9. A female .4phidius inserting an egg into the body of a living aphis, where the egg hatches; the larva grows to ma- turity by feeding in the tissues of the aphis. (From Webster) IFig. 1o9). Here the egg hatches and the young grub feeds on the juices of the aphid until it is itself full-grown, by which rime the aphid is exhat?sted and dead. Then the grub slits open the lower wall of the hol]ow corpse and spins a web between the lips of the opening and against the surface of the leaf below, which attaches the aphid shell to the support. Thus se- cured, the grub proceeds to give [178]
PLANT
