Whiteflies are common pest insects found on cotton, tomato, poinsettia, and many other plants. Nymphs are translucent and mostly sessile, feeding on their host plant's phloem (sap) from the undersides of leaves. They undergo incomplete metamorphosis into winged adults. Because whitefly nymphs cannot escape predation by moving, you hypothesise that their translucent bodies make them hard to spot by predators. How could you directly test this hypothesis?
A) Compare rates of predation on whitefly nymphs on plant leaves of different colours (for example, red versus green poinsettia leaves).
B) Compare rates of predation on whitefly nymphs coated with a nontoxic dye versus undyed whitefly nymphs.
C) Compare rates of predation on whitefly nymphs versus whitefly adults.
D) Compare rates of predation on whitefly nymphs by predators that are translucent versus predators that are not translucent.

Question

Quizplus · Accepted Answer

To directly test if the translucent bodies of whitefly nymphs make them hard to spot by predators, one could compare rates of predation on whitefly nymphs coated with a nontoxic dye (which would no longer be translucent) versus undyed whitefly nymphs. This would isolate the effect of translucency and determine if it affects predation rates. The other choices do not directly test this hypothesis. Choice A would test if leaf colour affects predation rates, but not translucency. Choice C would test if predation rates differ between nymphs and adults, but not if translucency makes nymphs harder to spot. Choice D is not a valid option since predators themselves do not vary in translucency, and it is not clear how this would address the hypothesis.

Whiteflies Are Common Pest Insects Found on Cotton, Tomato, Poinsettia