The Goldenrod Gall Fly Lays Its Eggs on the Terminal

The goldenrod gall fly lays its eggs on the terminal buds of goldenrod plants. Larvae chew through the buds and into the stems, where their saliva induces the plant to generate a gall, or outgrowth of tissue that then provides food and shelter for the developing larva. The larvae are prey to both parasitoid wasps and to birds; wasps selectively prey on larvae inside the smallest galls while birds selectively prey on larvae inside the largest galls. Goldenrod gall flies are therefore subject to _____ selection.

A) balancing
B) stabilizing
C) directional
D) disruptional
E) heterozygote