11 September 2018

What the caterpillers taught me this summer

It’s been an unusually interesting summer: first I began learning the names of our grasses and weeds, then I began finding fascinating fungi (because we’ve had so much rain) and then – then things got buggy.

Here are some of the highlights from the insect world:

I found a creature crawling up a tree on the traffic circle just north of the Green: a caterpillar-like being toting a sac that looked like a deliberate attempt at camouflage:


After some research I learned that it was a bagworm. They climb into a tree and hang there. The males hatch into moths and fly off to mate with the females (right through the sacs!), who then die without ever leaving their sacs, but leave fertile eggs behind: lots of eggs! In the spring the eggs hatch and eat – oh, no! Spruce trees! There was a spruce tree right where I’d seen this thing, so I checked it and removed four sacs:

Nearby I found something I knew very well. Do you?

That brown thing on the side of the trunk is a cicada casting. The cicadas live underground, sometimes for years, before climbing up onto something and breaking out of their old skins to fly off as handsome red-eyed insects that make a loud sawing noise at the end of summer. You don’t usually get to see the adults, but you can hear them!

And then – there were the caterpillars. You probably know that our monarch butterflies are in trouble. They lay their eggs on milkweed and a lot of milkweed has been destroyed by environmentally unfriendly agricultural practices. There’s plenty of milkweed on the Green, but I had never seen a monarch caterpillar on them. I thought we had the wrong kind of milkweed. But no! I found:

How exciting is that? This is what monarch butterflies look like:


But there’s more! Now, here’s a story: I was walking down a block where there were houses with little gardens out front and I saw what I thought was dill in one of them. And in the cracks in the sidewalk – little seedlings coming up! I carefully pulled out some of the seedlings to see if I could get them to grow on the Green, but as soon as I touched them I realized they weren’t dill: they smelled like licorice, so they must be fennel! Okay, I’d still like to grow them. So I took them home and put them in a mug of water. But they didn’t do well: the leaves kept disappearing. Disappearing? And then I saw that I’d brought home something besides seedlings: there were little caterpillars eating the leaves! And I recognized those caterpillars because I’d found some on my parsley at the Green! They were black swallowtails!

I knew those caterpillars ate parsley – because parsley is in the carrot family. But what were these doing on fennel? Well, it turns out that fennel is in the carrot family too – and when I later found yet more of those caterpillars feasting on our bishop’s weed I learned that bishop’s weed is also a carrot relative! Who knew? The caterpillars did! And now – so do we.