Prey handling of toxic and non-toxic Lepidopteran prey by Chinese mantid, Tenodera sinensis

Monarch caterpillars, Danaus plexippus, sequester toxic cardenolides from milkweed plants. This defense is effective against most predators, but the Chinese mantid, Tenodera sinensis, is able to consume them without any apparent ill effects. It has been shown that mantids consume monarch caterpillars by gutting them, allowing the gut material to fall from the prey without further consumption. They do not engage in this behavior when consuming non-toxic European corn borers, Ostrinia nubilalis, or wax worms, Galleria mellonella, suggesting avoidance of prey toxicity. We tested the prey toxicity hypothesis and the alternative hypothesis that the gutting behavior reflects a more generalized avoidance of lower-quality (i.e., less-nutritive) plant material. We reared monarch caterpillars and cabbage loopers, Trichoplusia ni, on toxic and non-toxic plants, and conducted behavioral trials observing mantid predator-prey encounters with these prey. We also conducted experiments in which we offered mantids starved and un-starved monarch caterpillars, reared on toxic and non-toxic plants, as well as corn borers.

Mantids gutted both toxic and non-toxic monarch caterpillars and cabbage loopers, but not starved monarchs (gut clear of plant material). This data rejects ‘the prey toxicity’ hypothesis but supports the ‘plant quality’ hypothesis. Intriguingly, mantids did not gut corn borers that recently fed on highly nutritive plant material (i.e., corn kernels). This suggests that mantids respond differently to caterpillars that ingest plant material of different nutrient content (seeds vs. leaves). Our data demonstrates that mantids are capable of fine-grained decision making regarding what prey organs are consumed versus discarded.