The Contented Naturalist

The idea of poison is really interesting among insects. Many plants have evolved toxins within their tissues, presumably because it reduces the amount of animals that eat them. But then several kinds of insects evolved not just tolerances, but preferences for these toxic plants. Insects like caterpillars (larval moths or butterflies) can build up those toxins in their flesh so that they too are distasteful to their predators. Probably the best known is the monarch butterfly, whose caterpillar eats milkweeds. Although predators don’t instinctively know that certain organisms are toxic, they learn quickly after trying to eat their first example. Think about what it felt like to eat the sourest, most bitter, foul-tasting thing you ever tried- that’s probably what it feels like to be a young bird that unknowingly tried to eat a plump monarch caterpillar! One young blue jay was observed trying to eat a monarch– it gagged immediately and repeatedly. What a horrible surprise that must have been for the bird!

To my knowledge, there’s no predator that evolved enough tolerance of toxic caterpillars enough to use the same toxins as their own protection (like the monarchs do with the milkweed they eat). In order to do that, the species would have to eat pretty much exclusively the toxin-carrying insect. Some predators do tolerate the chemical defenses, however, such as the Chinese mantis eating monarch caterpillars. A 2017 study by Jamie L. Rafter, Liahna Gonda-King, Daniel Niesen, Navindra P. Seeram, Chad M. Rigsby, and Evan L. Preisser (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5371951/) found the mantids did not suffer reduced body size nor produce fewer eggs when fed a diet including monarch caterpillars. I don’t know if that applies to our native mantids, though.

I wondered how insects can even taste poisons– they don’t have saliva and tastebuds like we mammals (or is it just humans?) do. It turns out that they do have tastebud-like sensors, just not mouth-based. Instead, they have tastebuds on their feet or antennae or even ovipositor. Wow! Guess the ovipositor makes sense, when you’re a ichneumon wasp that lays eggs on/in wood-boring beetle larvae. You need to tell if you’ve found a suitable food for your babies, while probing deep in the wood where you can’t see. Anyway, back to poison…

Some insects use poisons more offensively too– like wheelbugs who inject their prey with a nasty toxin that basically dissolves the victim’s insides, so the wheelbug can slurp up the resulting insect smoothie. That might be more like venom than poison, though, now that I think about it. Still, though, it seems like poisons are pretty useful to develop , considering how many plants and insects evolved them independently. I wonder if I can take poisons I’ve metaphorically consumed and turn them into something useful? Sure would be nice if I could turn toxic relationship messages into, say, a brilliantly colored elytra! (Who couldn’t use a nice jewel-toned protective shell now and then?) But since I can’t, I’ll at least try to avoid consuming known toxins,