That Tastes Yucky!

Lip-smacking good – crickets, earthworms, caterpillars, even some bees and wasps – yummy if you’re an insectivore that is! That’s what they call a creature which eats bugs.

I spend a lot of time looking at stuff. Sometimes I understand what it’s doing and sometimes I don’t. Recently, I have been plagued by Japanese Beetles who feast on every plant I love (and for some reason they avoid those plants I dislike) WHY? I was thinking with, the world-wide decline in insects why does it seem hardly anything eats these beetles? Could it be they taste bad? Or is there something else at play with Japanese Beetles?

We have all heard, some insects are brightly coloured to warn predators they taste bad – the Monarch Butterfly does this. But is this the case with these beetles? The Japanese Beetle first appeared in North America in the early 1900s and has devastated crops and gardens ever since! If you recall an article I wrote a while back for the Standard (Japanese Beetles – The Standard (thestandardnewspaper.ca), you might remember the immature (larval) stage is very different than the adult stage. In fact, the larva look very much like White Grubs and act much the same; spending most of their time in the soil. They are juicy and nutritious so lots of things eat them, e.g. moles, raccoons and skunks as they occur in abundance in our lawns. So it seems, at least the larval stage is palatable.

The adults are much different, a hard carapace (outer ‘shell’ or exoskeleton) makes them crunchy and perhaps hard to break open, to get at the juicy innards. But it seems, many predators can and do eat them. So why are they still doing so well? The answer lies in several factors. They are prolific breeders and exude a pheromone to make sure they can find each other when populations are spread out. They breed quickly and have lots of young which live in the soil, going deeper as the season progresses, so predators have trouble finding them. The adults feed on many species of our native plants, so finding dinner is never a problem.

Finally, there are few naturalized predators here, so even if an individual bird or mammal finds them edible, other predators may not have figured that out yet. I watched an Eastern Phoebe recently. Right beside it on a Trumpet Vine there were about 30 Japanese Beetles literally buzzing around in a sexual and feeding frenzy (yes I watched the whole thing LOL). The Phoebe totally ignored them and flew to the ground repeatedly catching other small insects. Were they softer and easier to catch and digest? Perhaps yes. So it seems the beetles don’t really taste bad; they are just in a new environment where the natural controls are not yet established. So they might taste good, but I’m still not tasting one!

It takes time, but predators do adapt and over time can have a controlling influence. Diseases may morph and also eventually impact these beetles. One hopeful sign is the presence of tachinid flies, which parasitize many caterpillars, sawfly larvae, beetle larvae, earwigs, grasshoppers and many more insects – and best of all they parasitize Japanese Beetle adults! Tachinid flies have several intriguing egg laying strategies. In some species, eggs are laid on foliage near a host insect; the eggs hatch and the maggots are consumed by the host insect when it feeds on the foliage; then the maggots feed on and develop in the host insect killing it. In other species, tachinid females have long ovipositors which they use to pierce the skin of the host insect and insert their eggs. In yet other species (the Winsome Fly), the adult tachinid glues her eggs somewhere on the outside body of the host, the eggs hatch, and the maggots penetrate into the host’s body. This is the most common strategy we see for tachinids which attack Japanese Beetle adults – so there is still hope!

Geoff Carpentier is a published author, expedition guide and environmental consultant. Visit Geoff on-line on LinkedIn, Facebook and Instagram.

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