moths – Page 19

Homes for the winter

Here’s some of those photos I’ve had sitting around for a while, waiting for an opportunity to post about them. This first one I’ve had since January! I came across this interesting structure while out with Blackburnian during the Colour-coding Chickadees walk. I had no idea what it was at the time. It was already open when I came across it, and there was nothing in it. It resembled a cocoon, but I didn’t really know. Lots else to post about, so I never got around to looking it up.

Then in mid-February, Jennifer over at A Passion for Nature posted a cocoon she’d been seeing on some of her walks, and a couple days later she posted a follow-up about the cocoon’s occupant. Turns out, it’s the cocoon of a Cecropia Moth, one of the North American silk moths, a group of beautiful, giant moths whose caterpillars spin “silk” which they use to create their cocoons. Jennifer directs her readers to a rather amazing site that documents the life cycle of the moth from egg to adult (and now I’ll direct you there, too!). The site indicates that the moths overwinter as pupae, so the fact that this cocoon is split open likely suggests that it’s either last year’s case, or somebody/thing got to it before I did this winter.

This second one is also a moth, and I’ve also had it on hand since January. I knew right away what this one was when I saw it, from having browsed through the Moth Photographers Group website while identifying a few moths last fall. Of course, I couldn’t remember exactly which it was, just that I’d seen it on the pages, so I had to go back and scan through their many (very useful) pages all over again.

The case, which superficially reminds me of those made by caddisfly larvae, is made by a moth belonging to the group of “bagworm moths”. This one’s probably Psyche casta; the different species have different case styles, but I would assume some of them to be subtle. Like the caddisfly, the moth larvae tote this bundle of sticks around with them until it’s time to pupate, at which time they affix it to a solid surface for the winter. I found three of these all sitting in the window frames of my parents’ house. Two were between the panes of glass, but this third one was on the interior frame, which made it easier to photograph, but also meant it was exposed to spiderwebs, dust, pet hair, etc.

Wikipedia indicates that many bagworm moth females have vestigial wings, and sometimes never leave their cases, mating with males even while still inside. They die after mating, either having laid the eggs inside the case, or without having laid the eggs (so the larvae mature and emerge from the female’s body). The eggs are very hardy, and a bird that finds the case and eats it will pass the eggs through its digestive system intact, aiding in the spread of “new blood” from one area to another.

And this final case isn’t a moth or butterfly cocoon, but instead was created by a Praying Mantis. They started appearing late last fall, and I think I found five in total, four of them laid on the research station’s exterior walls. I didn’t know what this was at first, either, but I think one of the volunteers at the station pointed it out and identified it for me. They were still there, all of them, when I was back for the start of the spring season. When they were first laid they were a little gooey to touch; now they’re all quite hard.

I read somewhere that they’re always laid on the south side of the object they’re affixed to, which is actually true of the four on the station building. The one pictured here, however, found at the base of a metal signpost, was on the north side. I guess that one didn’t get the memo. Mantids are fairly common at the spit, which is pretty neat, since I never saw many growing up. Despite their slightly startling, ferocious appearance, they’re pretty tame to pick up and handle, not inclined to bite, which makes them great for showing to kids. Just like hatching a cocoon, you can bring these cases inside and set them up in a terrarium to hatch – or, if you don’t want to risk damaging the wild ones, you could order your own Praying Mantis Encounter from Discovery Channel’s store, and treat the kids (or yourself) to a neat experience watching them grow. Only available to the US, unfortunately, or I’d order one! :)

Cotton candy for blackbirds

Edit: This post was recently included in the 182nd edition of the Friday Ark, a blog carnival focusing on animals of all sorts.

I’m sure we’ve all seen these in our local wetlands, cattail heads that have become all poofed out as winter progresses, like so much cotton-candy on sticks. I’d never given it much thought before, and if I had I suppose I’ve just assumed that the fluff has something to do with the cattail releasing its seeds to the wind, much like milkweed does.

A few weeks ago, my mom bought the book Insects: Their Natural History and Diversity (with a photographic guide to insects of eastern North America) by Stephen A. Marshall. Steve Marshall is a prof at the University of Guelph, where I did my undergrad, and was one of the instructors leading the Ecuador field course that I took. I didn’t spend much time with him (I knew the other prof better), but he was a really nice guy. So I thought it was cool that Mom had got this book, and I sat down to leaf through it. I was primarily interested in the 40-someodd pages of moth plates, and while flipping through those I spotted an image of fluffy cattail heads. Intrigued, I read the plate caption associated with the figure.

Turns out, those fluffy cattail heads you see in the middle of winter aren’t just the cattail doing its thing. Sure, it will naturally begin to loosen the fluff and lose some to the wind. But the cotton-candy formations? They’re the work of a tiny, drab little moth called the Shy Cosmet (Limnaecia phragmitella). Its caterpillars are appropriately known as Cattail Caterpillars. They feed on the seeds of the cattail in the fall and spring, overwintering inside the head as a larva. In late spring they pupate and emerge as an adult moth in early summer.

In order to ensure that they have a secure home for the entire duration of their stay, they spin tiny silken threads that act as a web holding all the fluff inside. The cattail will still loosen its seeds from the stalk to try to spread them on the wind, but the caterpillar’s netting holds them in place. The result is a rather lumpy cotton-candy appearance.

I thought this was all pretty cool, so I did a bit of searching on the web and discovered a post about the Shy Cosmet, made recently, by Gerry Wykes at Naturespeak (he calls Detroit home, so is within my rather broad neck of the woods). In it he brought in a cattail head and gently dissected it to expose the caterpillars hiding within. Now, I suppose I could have just taken him at his word, but I really wanted to go out and have a look for myself. Insatiable curiosity. In the name of science, of course. I brought in two heads for good measure, and opened them up in a tub to contain any wandering worms.

Gerry indicated that it would take a moment or two for the caterpillars to poke their heads out of the fluff, that they wouldn’t be immediately visible. So I sat there and patiently waited. And waited. Nothing happened. No heads, no tails even, not a hint of movement. I’ll admit that they should all be dormant at this time of year, but since he’d had such luck with his coming out as soon as they were warm, I was beginning to wonder if I’d picked a dud cattail head, one that really was simply just loosening up its fluff.

So I started gently teasing apart the clumps. I found lots of what looked to be frass in with all the seed heads. The seeds are tiny, flat and boxy at the end, and brownish in colour. The frass, on the other hand, was gray and round, spherical. There was lots of it, but no caterpillars associated with any of it.

Finally, after standing with my head bent over this dish for many minutes, I discovered one. Only one, just a single, lone, under-developed caterpillar. Perhaps the cattail head had already been picked over by foraging birds and this was the only guy to have survived. Perhaps there never were many to begin with, maybe I missed one or two. But I went through the entire two cattail heads and only found one. By the time I was done, they looked like this:

Here’s the caterpillar. I found him tucked in a clump of relatively undisturbed fluff, nearly comatose. He wiggled a bit when I first picked him out, but didn’t go anywhere. Gerry was describing his caterpillars crawling all over the place, making getting a good photo difficult. Mine was very photogenic.

This is the caterpillar posed with my mom’s finger for scale. He was tiny. Tiny tiny. This is why I wouldn’t be surprised if I missed a couple others, although I was paying close attention. Below is the caterpillar beside a measuring tape. You’re looking at the inches side of the tape. Each one of those black dashes is 1/16″. See? Tiny tiny, it’s not that my mom has big fingers…

I actually found the dried husk of an older caterpillar in the fluff as I was starting to clean up. This gives you an idea of what it should grow to before pupating. He’s got a ways to go.

These little caterpillars form one of the primary food sources for Red-winged Blackbirds upon their arrival here in the spring. It seems like they’d need to eat a lot of them to get much nutrition, but evidently it works for them. A couple springs ago I got a photo of a female Red-wing poking at cattail heads. I thought at the time she was looking for nesting material, but having learned this, it seems apparent that she was actually searching for caterpillars. Who knew? Cotton candy indeed.

As for the book, I highly recommend it. It’s got great photos for an identification reference, and excellent information to complement them. The notable entomologist E.O. Wilson is quoted on the cover: “I wish I’d had Stephen Marshall’s book when I started out in entomology. Its countless photographs and notes bring alive the vast diversity of the insect world.” That’s like Roger Tory Peterson endorsing a bird reference book. There’s so much cool stuff in the book, lots to look at. The only downside: it weighs a tonne. Probably almost literally. At 730 pages and nearly two inches thick, a field guide it’s not. Still, it has the best collection of printed moth photos I’ve seen, plus so much other stuff, I ended up getting a copy myself (should be in the mail). It retails in store for $95, though generally cheaper online, but I found a copy on eBay for $33 plus shipping, so if you look around you should be able to get a good deal on it. Amazon has it on sale for $60. It’s also got a couple images of inside the book so you can take a peek before you buy.

Cattail thwacks revisited

Edit: This post was recently included in the 180th edition of Friday Ark, a weekly blog carnival focusing on animals of all sorts. You can check out the full edition at The Modulator.

One of the downsides to learning things yourself using the internet or reference books as your guide is that it’s pretty easy to mis-identify something based on poor photographs, incomplete descriptions or information, or just vague or ambiguous wording, particularly if you have a notion about what you’re expecting. In one of the posts I did mid-January, about fungus in the woods in winter, I mentioned a large, creamy, fuzzy mass I observed on the trunk of a tree that I identified as a slime mold. Well, Jennifer over at A Passion for Nature corrected me on this by (correctly) suggesting that it looked like a gypsy moth egg mass.

I went back yesterday to the same area and had another look at it. The particular one I photographed still looked and felt (to my frozen-numb hands) like a cattail thwack with no particular distinguishing characteristics (I didn’t want to try taking it apart because I don’t like to disturb). However, upon closer investigation, I started noticing more of these fuzzy blobs on nearby tree trunks, pretty much all within a few feet of the ground. Some of them had much more obvious visual characteristics that may have led me to the eggs conclusion if I’d seen them first. In the above and the first photo you can actually see the individual eggs wrapped up in all the little hairs that create the fuzzy mass (I think the first photo may actually be hatched eggs from last year? It’s hard to tell, but the dark spots are very pronounced). The hairs are made by the female moth as she’s laying her eggs, and are hypothesized to protect the eggs from potential rodent and avian predators by discouraging them from getting the hairs in their face and nostrils and irritating the skin.

Gypsy Moths aren’t native to North America (like a lot of common wildlife). Rather, they were brought over to Medford, Massachusetts in 1869 by French astronomer Leopold Trouvelot, who also had an interest in insects and was hoping to breed a sturdier, more productive silkworm. Well, like often happens, the moths escaped and it didn’t take them long to settle into the new landscape. They’re now found into eastern Canada as far north as Maine and the Maritimes, as far south as northern North Carolina, and currently west into mid-Wisconsin. When you consider the size of the insect in question, it’s a pretty good area to cover over that period.

The moth’s dispersal is also made more interesting by the fact that the female moth, the recognizable white Gypsy Moth, can’t fly. When she emerges from her pupa she’s full of eggs and way too heavy to get airborne. Male moths (which are brown) can fly, and will travel long distances to reach a female, which they detect using the broad, fluffy antennae that only males possess. These antennae are specially designed to pick up the pheromone molecules released by the female when she emerges. Near a couple of the egg masses I found pupa cases left from the female when she emerged. The cases also have hair tufts that presumably protect them the same way the hairs in the egg mass do.

Still, if the females aren’t moving, then the eggs are going to be laid near where the female emerges, which also doesn’t help much with dispersal. Instead, dispersal is carried out by the caterpillars (weird, eh? The only ones without wings). Caterpillars, during the course of their feeding, climb to the top of the tree and then spin a line of silk which they use to “balloon” on the wind over to the next tree. I can’t imagine this taking them very far, so it would be a very slow dispersal.

This photo (used with permission) is of a female caught in the act of laying an egg mass in late summer. She was found inside a porta-potty, so I can’t imagine the caterpillars would have much to eat when they hatch, but I gather Gypsy Moth females aren’t too particular about where they lay their eggs. The larvae will feed on up to 500 different species of trees, but particularly favour oak. Most of the egg masses I came across were on rough-barked tree species, primarily Black Cherry. Caterpillars hatch from their eggs in early spring, late April into early May. They feed on tree leaves and can be a severe pest in some areas where they completely denude trees of their foliage, particularly since a single egg mass can contain up to 500-1000 eggs. In late June to early July they begin to pupate, and emerge as adult moths after a couple of weeks. Females lay egg masses shortly after emerging, and adults will never eat. Adults die shortly after mating, and the species overwinters in the form of these egg masses.

It’s funny how once you know to look for something, it suddenly seems to jump out at you everywhere. Now that I’m aware of these and what they are, I’ll be keeping my eyes open for them on future walks.