A researcher discovered a species of moth, Nemoria arizonaria, that lays its eggs on oak trees. Eggs are laid at two distinct times of the year: early in spring when the oak trees are flowering and in midsummer when flowering is past.
Caterpillars from eggs that hatch in spring feed on oak flowers and look like oak flowers. But caterpillars that hatch in summer feed on oak leaves and look like oak twigs.
How does the same population of moths produce such different-looking caterpillars on the same trees? To answer this question, the biologist caught many female moths from the same population and collected their eggs. She put at least one egg from each female into eight identical cups. The eggs hatched, and at least two larvae from each female were maintained in one of the four temperature and light conditions listed below.
When this experiment is performed, caterpillars from Groups 1, 3, 5, and 7 end up looking like Oak Flowers and caterpillars from Groups 2, 4, 6, and 8 end up looking like Oak Leaves. Based on these results, which of the variables was/were most significant in determining the morphology (look) of the caterpillars?