Bruce Spanworm

Bruce Spanworm, Operophtera bruceata

It’s getting to be very late in the year for moths. Winter approaches, and our warm days now are lucky to make double-digits Celsius (>50°F). Hardly anything comes to the porch lights in the evening now, as by nightfall the temperature has dropped too much for anything to be flying. However, there are still some cold-hardy species out and about.

I discovered this one resting on a leaf in the forest when I was out with Raven a few days ago. If it had been on the trunk of a tree, or a fallen log, or even on a dead leaf on the ground, I likely would have walked right by, but it stood out on the green leaf. It’s a Bruce Spanworm (Operophtera bruceata), one of the latest moths to be on the wing. The first ones appear here in late October, and they fly on warm days (and on warmer evenings) through November. They can handle the cooler daytime temperatures because they’ve got a very high surface:volume ratio – that is, they’re very narrow, with lots of surface area, so they absorb the sun’s rays and ambient temperature more quickly than a thick-bodied moth would. (There are thick-bodied moths on the wing now, too; they’re invariably fuzzy, which helps to insulate them.)

They’re very similar to the Autumnal Moth (Epirrita autumnata), which is also a fall flier (as the name suggests) but not quite as late. They first appear in late September, and their flight window barely overlaps with Bruce Spanworm. However, you can easily tell the two apart by the dots along the outer edge of the hindwing – in the Autumnal they’re paired at the end of each vein, while in the Bruce there’s just a single dot. The Bruce is also slightly smaller. The Autumnal below is one I photographed last year.

The day after I saw and photographed this Bruce, which was the first one I’d seen this season, I spotted another fluttering low to the ground in our front yard. By the time I had retrieved my camera, it was gone. It might well be the last moth I see this year, if the long-term forecast is to be believed.

Autumnal Moth

Tussock moth cocoon

Cocoon of White-marked Tussock Moth, Orgyia leucostigma

Periodically I pause to check the three great, old maples in our front yard for interesting goings-on. I’m not looking for anything particular. An interesting bug, perhaps. Some fungus maybe. Whatever’s happening on the trunks at the time. Sometimes there’s nothing at all that catches my eye. But about a month ago I spotted these. There were three of them, two on the biggest maple, and one on the third. I’ve continued to check on them, from time to time, as I do my maple trunk surveys; they’re still there, and I expect will be for the winter.

It was pretty obvious to me from the outset what they were: those hairy, oval masses couldn’t be anything but moth cocoons. But what was the hard foamy mass on the outside? I had a suspicion, but I took some photos and came inside to confirm.

Cocoon of White-marked Tussock Moth, Orgyia leucostigma

Sure enough, the answer was on page 71 of the fabulous Tracks & Sign of Insects. The cocoon belonged to a tussock moth. This group of species lays their eggs on the outsides of their cocoons – because the females are flightless, and so don’t travel far.

That answered what. But what about who?

Cocoon of White-marked Tussock Moth, Orgyia leucostigma

I noticed as I was examining them that inside the hairy cocoons were the hard shells of pupal cases. I couldn’t really tell if there was still a moth in the case or not, so I reluctantly peeled one off the tree to see (I don’t like to disturb things usually, if I can help it). As I flipped it over, I noticed two things. The first was that the case was empty. I hadn’t yet gone in to look up the book at the point that I was examining the cocoon, but if, as I suspected, the white mass was eggs, then it wasn’t a great surprise that the case was empty.

But the other thing that was obvious was the three white spots on the back of the case, remnants of the outfit the individual wore as a caterpillar. This quickly answered the who: this was the cocoon, and egg mass, of a White-marked Tussock Moth (Orgyia leucostigma). Caterpillars of this species are striped lengthwise with yellow and black, bearing three long, dark tufts at the front and rear, and four short, thick white tufts along the back. Very distinctive!

The species overwinters at the egg stage (which makes sense if they were laying them in the fall). Caterpillars are about as generalist as they get. Caterpillars of Eastern North America lists as possible host plants “apple, birch, black locust, cherry, elm, hackberry, hickory, oak, rose, willow…fir, hemlock, larch, spruce and other conifers.” They’re fairly common, so you might well find a cocoon or two if you try checking out some old, ridgy trees.

Here’re a few photos of the species, including one of a female in the act of laying eggs (how cool!).

White-marked Tussock Moth Caterpillar
White-marked Tussock Moth Caterpillar by cotinis on Flickr (CC licenced)
White-marked Tussock Moth, view from behind - Moth is looking "furry"!
White-marked Tussock Moth, view from behind by Vicki's Nature on Flickr (CC licensed)
8316 - Orgyia leucostigma - White-marked Tussock Moth
Adult male White-marked Tussock Moth

 

Extending the feeding season

Poplar leaves with green spots from Ectoedemia larvae

One of my primary reasons for starting up this blog, nearly three years ago, was that it would encourage me to learn new things about the world around me. And so it has. Most of the time it’s through my discovery of something interesting or unusual that I come across while out hiking (or sometimes it comes to me), and which I then look up more info on once I get home.

Recently, I was approached about whether I might be interested in slightly revising my book review of Tracks & Sign of Insects, which I’d posted here on the blog back in May, for inclusion in a Vermont-based magazine called Northern Woodlands. The magazine is an interesting mix of articles, somewhere at the meeting place of forest “management”, forest exploitation, and forest appreciation. I admit to being a bit of a purist – the thought that some people feel the need to “manage” their forests in order to make their forests “healthier” really bothers me, and while I recognize the need for lumber and tree harvesting (and even don’t mind most forestry practices, to some degree), it still hurts my heart a bit to see a forest put to that use.

So when I got my copy of the magazine in the mail, I skimmed over all those articles. There are still quite a number that fall into the “appreciation” category, however, and more than once I found myself thinking, I didn’t know that, that’s so neat!

Poplar leaves with green spots from Ectoedemia larvae

One such article was relatively fresh in my mind while I was out walking our own woods a couple of days ago. We don’t have very much woods, or at least not walkable woods, here on our 30-acre parcel (most of it is down the road at the 100-acre bit). Much of what occurs here is wet, especially at this time of year. There’s a small patch near the back which I sometimes cut back through and then wander along the strip of forest at the edge of the property (actually just the edge of a larger expanse of woods, but the fence of the property line runs through it and only a little bit bleeds over from the neighbour’s land onto our own).

I was watching my step as I came around through the trees, making sure I didn’t trip over anything, when I spotted these leaves. A month ago, before I’d received the magazine, not only would not have known what was going on here but I probably wouldn’t have even noticed them in the first place, mixed in with the rest of the fallen leaves (see top photo). But there’d been a short half-page article on them in the magazine, and so stopped and gathered a bunch together so I could take a photo to share with you guys here on the blog.

Poplar leaves with green spots from Ectoedemia larvae

You’ll have noticed that they’re all poplar leaves, and that all of the leaves seem to have one section of the leaf, in most cases between the first and second major diagonal veins, which has remained green. A closer inspection reveals a small blemish at the base of this green strip, butted up against the mid-rib and the lower vein. If you examine this under magnification (some folks carry pocket loupes in the field with them, but if you lack one you can flip your binoculars upside down and look through the wrong end, holding the object a centimeter / half inch away from the lens, to the same effect) you’ll see a little worm tucked in the blemish.

The worm is a caterpillar of a moth in the genus Ectoedemia. It’s just a little moth, less than a centimeter/half inch long, with long, narrow, blue-gray wings and a fluffy orange head. The caterpillars are late feeders – perhaps a strategy to avoid the predation pressure of breeding birds searching for food for their young? – feeding on the leaves well into the fall. So late, in fact, that the leaves drop from the trees while the caterpillars are still munching on them. It does the caterpillar no good to be chewing on a dead leaf, so it ends up secreting a type of plant hormone that keeps the leaf alive for a while longer. The article doesn’t specify, but I suspect that, given this strategy, the caterpillars cocoon within the fallen leaves and then pupate and emerge as adults in the spring.

Ectoedemia sp?
I think this might be an Ectoedemia sp. Or it might not be. Those little micros are so hard to ID. (Also hard to photograph well, but that's a different problem.) But if it's not, well, the Ectoedemia sp. adults look an awful lot like this, anyway.

 

Moths and ants

Hummingbird Clearwing, Hemaris thysbe

First, a note to say that The Moth and Me #13 is finally up at Today in NJ Birding History. Better late than never, as it’s got a great collection of moth-themed posts pulled together into one spot. Make sure you swing by to check out all the mothy goodness!

And second, I thought I’d take a break from work on the moth guide long enough to share a couple of recent insect sightings. The first, above, is actually a moth as well: a Hummingbird Clearwing, Hemaris thysbe. Dan was the first to discover these guys out in our garden, noticing them visiting the phlox in the evening. I’d been watching for them, but had yet to see any. I’ve even planted some Liatris, Blazing Star, expressly because I knew the clearwings liked to visit them during the day. I don’t know what I’d do without Dan to find all these neat things for me.

Hummingbird Clearwing, Hemaris thysbe

Dan caught one of the moths using my butterfly net and tucked it in the fridge to cool for photos. The top photo is of the moth after its photo session, still cool enough that it sat quietly on Dan’s finger. They were relatively unwary, as insects go, allowing for fairly close approach as they went about their business in the garden. My Liatris just has a couple of flower spikes, but we have wide swaths of phlox and it was to this latter plant that they seemed to primarily be coming.

Hummingbird Clearwings are not much smaller than their namesake garden birds, and from a distance quite resemble them as they hover at the flowers sipping nectar. They are day-flying moths, and can be encountered anytime during the daylight hours, though I find them to be more active in the evening. In the larger patches of phlox I find I often notice them first by sound, rather than by sight, as their wings beat so fast as to produce a loud buzz, more distinctive even, perhaps, than that of a hummingbird’s wings.

Hummingbird Clearwing, Hemaris thysbe

They are one of the most readily seen of the sphinx moths in our area, if only because the majority of the others fly at night. In a garden with appropriate nectar flowers – phlox, liatris, and bee balm are favourites – they’re not even that uncommonly seen, but if your garden lacks good plants, or if your surrounding area is missing the caterpillars’ host plant (hawthorn, honeysuckle and Prunus species such as cherries or plums), you might never see one. I was in university before I saw one, which surprises me a little, as there were certainly plenty of the host plants where I grew up, and my mom maintained a beautiful garden of perennials. Was I just not looking for them before that?

Hummingbird Clearwing, Hemaris thysbe

I really wish this photo had been in focus, but at least you can still see the moth. And in particular, you can see its long proboscis, curled as it flies from one flower to another. The proboscis is a hollow tube that the moth uses to suck up nectar, and in this species is nearly as long as its body. Often the length of the proboscis corresponds to the length of the flower tubes that the species prefers to visit, and indeed both phlox and bee balm are long-tubed flowers.

(This reminds me of the Darwin’s Comet Orchid, Angraecum sesquipedale, a Madagascar species with an incredibly long nectar spur that is only pollinated by a species of sphinx moth with an incredibly long proboscis – 12 inches long, in fact. I first saw this in a nature documentary on tv, but through the wonders of the intarwebs, you can watch the segment here on YouTube.)

Ants with aphids

On to other observations. A couple of days ago we made our last visit of the summer to our Blue Lakes MAPS site. It was quiet again – we suspect widespread breeding failure in our region, as the last few visits have been universally slow at all of our stations, a period when typically we’d be catching lots of young-of-the-year as they disperse from their natal territories. Even the woods were quiet, with very little bird activity, just the odd small flock here and there and hardly any late-summer birdsong. Given that birds were sparse we had to pass the time in other ways: reading a book, taking a nap, or, you know, looking at other things.

There were a handful of small saplings near the side of the path in one of the clearings that were absolutely covered in ants. After a couple of empty net checks I finally took my camera along to try to peer a bit closer.

Ants with aphids

The ants were only on these four or five trees, all of them Trembling Aspen (Populus tremuloides). They were congregated thickly along the thin twiggy trunks and side-branches, with very few bothering with the leaves. I had a feeling I knew what was going on, and sure enough, upon close inspection I could detect aphids on the bark where the ants were thickest. I blew a few of the ants off to try to get a photo of the aphids (below), but the ants were quick to move in to take their sisters’ places, so I had to be quick. It’s not the greatest of photos, as I just had my wide-angle lens with me and not my macro, but it’s sufficient for getting the idea, anyway.

Ants with aphids

I’m not sure what species of aphid this is, though Chaitophorus stevensis, a specialist on Trembling Aspen, is a possibility. Some aphids will pierce the soft bark of young twigs or stems, while others will target the thin membrane of leaves or leaf veins. These ones seemed to be of the former group. The ants are there as “farmers”, tending the “herds” of aphids and harvesting the sugary secretions of honeydew much the way humans maintain herds of Holstein cattle to collect their milk. The aphids benefit from having the ants around, too, as the ants stand around with their formic-acid shotguns and chase off any wolves or competing farmers from their herd.

Of course, the aphids aren’t entirely given a choice about their situation: in some ant-aphid relationships, the ants will actually bite the wings off the aphids to prevent them from leaving; in others, chemical secretions from the ant stunt the development of the aphids’ wings. The same chemicals on the ants’ feet that they use in laying communication trails for other ants are also used as a tranquilizer, keeping their aphid herds calm and subdued (though it could be argued that actually the aphids are simply recognizing which side their bread is buttered on and using the chemical trails as a boundary marker so they don’t inadvertently wander off too far).

That’s all for this week. Back to the grindstone!

Hatching a pupa

pupa

Two weeks ago, the same weekend Dan walked back with me to show me the jewelwings, he pointed out what he thought was a chrysalis that he’d spotted dangling from the branch of a shrub alongside the path. (This was the primary purpose of the expedition; the jewelwings were a nice addition.) When I stooped down for a closer look, it turned out not to be a chrysalis at all, but actually the pupa of a moth that had slipped out of its silken cocoon. (Butterflies, when they pupate, form hard-shelled cases without any additional protection, while moths usually form soft-shelled pupae that they encase in a cocoon spun with silk fibres, sometimes incorporating other material such as leaves.) The fibres of the cocoon were still affixed to the branch, but now the pupa dangled delicately from one end. From rain, perhaps, or other weather effects?

pupa in mason jar for rearing

I took a few photos of it in situ, and then (at Dan’s suggestion) carefully broke the branch off to bring it back to the house to try to rear it and see what was inside. I placed the twig into a large, clear mason jar, crumpling up a tissue and placing it underneath one end so that the pupa would be elevated from the floor of the jar, aware that the moth would need room to be able to stretch its wings out as they dried. I covered the top with cling wrap to keep the moth inside until I found it, poking half a dozen holes into it with the tip of a pen to allow air circulation. And then I put it on the kitchen counter and waited.

[prob] Olethreutes albiciliana

Four days later when I came home from work, Dan pointed out a moth inside the jar. But it wasn’t the moth I was expecting to be inside the jar. Not that I had any idea, really, what species was inside the cocoon, but I did know that as the pupa was about 15mm (3/4″), the moth inside it would also need to be at least that big. The moth fluttering about the jar now, scurrying over the cling wrap and around the glass walls, was just a little micro, less than a centimeter (1/2″) long. I jarred it and placed in the fridge to cool, with the intention of slowing it enough that I might be able to manage a decent photo to identify it. I eventually got one through the clear plastic of the container, but it was sufficient to pick out a probable ID: Olethreutes albiciliana, a member of the family Tortricidae for which there is several records but no detailed life history information on the web. The records I’ve found have been for Alberta, Ontario, Indiana, Massachusetts and Vermont, suggesting it’s primarily a northeastern species perhaps extending west through the Boreal. I don’t recognize the plant it was attached to, but the substrate the caterpillar pupates on isn’t necessarily the same one it was feeding on.

Pupal case of [prob] Olethreutes albiciliana

A closer look at the plant revealed this tiny pupal case affixed to the twig at the base of some leaves. It looks a bit like a mantis or some other bug, but the long hooked “arms” are just bits of the pupa that split along thinner creases in the shell when the moth forced its way out, probably where the pupa traced the antennae (if you look closely at the top photo you might see that the pupa clearly shows an abdomen, two sings wrapped around the front, and the antennae folded down against the body in front of the wings. It even sort of shows the eyes, though they’re harder to see). It’s funny that I hadn’t even noticed this one when I broke the twig off and brought it inside.

pupa with cap sawn off by Ichneumonid parasite

It was a longer wait for the original pupa to “hatch”. Finally, when I came home from work yesterday afternoon, two weeks after collecting it, the top of the shell had been neatly popped off and lay on the floor of the jar.

And running around the mouth of the jar, under the cling wrap trying to find a way out, was the adult that had emerged from it. But it wasn’t a moth at all. It was a wasp!

[prob] Ichneumon annulatorius

I chilled this guy, too, and then took a couple of photos which I posted to BugGuide. The long, narrow body and antennae identify the wasp as a member of the family Ichneumonidae, a group of wasps that parasitize the larvae of other insects, primarily lepidoptera (moths and butterflies) and beetles. The expert on BugGuide placed it in the subfamily Ichneumoninae, and I browsed through the BugGuide catalogue till I found a possible match: Ichneumon annulatorius, based on thorax and leg markings and lack of white on the antennae. This species also seems to be a northeastern species, based on the locations of specimens submitted to BugGuide for ID.

This PDF had some useful information about the group, including the species I. annulatorius. The wasps emerge and mate during the summer and fall. The females then spend the winter hidden under loose bark or sometimes moss on trees or logs. In the spring, they begin searching for a suitable lepidopteran host, either caterpillars or newly-formed pupae, and lay their eggs, fertilized using the sperm they’d stored over the winter. The wasp larva develops in the pupa and emerges a few weeks later to start the cycle again.

This individual is a male, as it lacks a long, thin ovipositor at the tip of its abdomen. After I’d got my couple of photos I let him go so he could find himself a female. Interestingly, though, the paper notes, “Specimens may also be held for months at room temperature by supplying ample water and nutrients in the form of a 50/50 honey/water mixture.” If you think of the amount of time between when a female would have emerged from her host pupa in the summer, to when she lays her eggs the following spring, they actually have a reasonably long lifespan, for an insect. Although I don’t think the males sting, lacking the ovipositor (which is the organ that stingers are modified from), it’s hard to think they’d make very good pets.