October 2010 – Seabrooke Leckie

Tussock moth cocoon

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.

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?

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 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

Thimbleweed

For the most part, we (or at least I) most often take notice of wildflowers while they’re blooming. The colourful blossoms are at their showiest, catching our attention. When I try to bring to mind exceptions, one that stands out is Common Milkweed, as the drifting seeds from the dried, split pods are difficult to miss, especially when illuminated by the low autumn sun. Common Mullein might be another, the stiff, woody stalks lasting long into the winter and often the following spring, eventually one of the few bits of meadow life still poking out above the deep beds of snow.

To that category I’ll have to add Thimbleweed, Anemone virginiana. These plants bloom during the summer months, June through August. We have, it turns out, quite a few of them scattered randomly through our fields, and a number of them grow not too far from the trail that cuts through the grass. And yet, during the summer I don’t recall even once making a note of the plants. It’s only been since the flowers have died and the seed heads developed that they drew my eye.

The deeply sharp-lobed leaves at the base of the plant, and the evidence of similar (though now dead) leaves partway up the stems, told me this was an anemone, and a bit of poking around reveals it to be Thimbleweed (sometimes clarified as Tall Thimbleweed to distinguish it from the similar Long-fruited Thimbleweed). The name, of course, comes from the seedheads which do look an awful lot like thimbles, and are about the right size as well. When flowering they have typical anemone blossoms, five-petaled and white, pretty but unassuming, which is perhaps how I missed them all summer.

Anemones are generally woodland plants, but some, including Thimbleweed, can be found growing out in the open, though usually within sight of the woods. It seems to have a preference for dry habitats, but is adaptable and will also grow in moist soil. As the fall progresses, those thimble-like seedheads will open up, releasing puffs of cottony seeds, not dissimilar to those of milkweed and dispersed by the same means.

Interestingly, the plant isn’t often eaten by mammalian herbivores because the leaves contain a compound that can blister the inner membranes of the mouth and stomach. Perhaps the same chemicals that cause this made it useful to Native Americans as a medicinal plant, used as an expectorant (thins mucus so it can be more easily coughed up), an emetic (triggers vomiting), and an astringent (shrinks body tissues to reduce swelling or irritation). Smoke from burning the seed pods was also used like smelling salts, to revive the unconscious.

Broccoli lovers

We were treated to a surprisingly mild day today – around 20°C (68°F), which is beautiful for this time of year. It would have been nicer if it were sunny rather than overcast, but in late October in Ontario you really can’t be picky. I took Raven for a walk (despite that we stayed on our 30 acres, I wore my orange vest just to be on the safe side as I’d heard gunshots from the neighbour’s property earlier in the afternoon) and then bedded down the strawberries before returning indoors.

I never got around to harvesting the last of the broccoli this season. It was my first year growing broccoli, and I kept waiting for it to get a bit bigger, but before it got bigger it would undergo a growth spurt and start flowering. I got a few heads, but the last couple I missed. When they started flowering I decided just to leave them; maybe I could get some seeds off them when they were done.

I noticed, while I was in the garden tending the strawberries, that the plants are still flowering merrily away. Aside from the odd clover here and the stray aster there, they’re pretty much the only thing in the landscape that still is. This fact hasn’t gone unnoticed. The warm weather this afternoon had some late-season pollinators out looking for flowers to forage on, and they’d all converged on this small patch of yellow blossoms. I’d left my camera up at the house while I took the straw down to the garden, and couldn’t resist going back for it to document some of what was crawling over the plants.

There were three bumblebees (three!) visiting the broccoli flowers. At first I thought this one was Tricolored Bumble Bee (Bombus ternarius), by default due to the orange, though there are actually a few species that sport the orange bands on the abdomen. The most common in the east is Tricolored, but we also have B. sylvicola (no common name) and Red-belted Bumble Bee (B. rufocinctus).

I spent a while puzzling over the photos on BugGuide.net, trying to decide what the differences were between the species, before getting frustrated and Googling a North American bumblebee identification page. I discovered this great ID page, which is found at Bumblebee.org. It seems to have originally begun as a UK site – if you Google “bumblebee guide”, most of the first couple of pages are UK sites, and I get the impression they’re much more into their bumblebees there than we are here.

In any case, that fabulous ID key (now bookmarked!) pointed me to Red-belted Bumble Bee, primarily due to the orange butting up against the black on the abdomen – the other species all have a yellow band between them.

Bumblebee species #2 is, I’m fairly certain, a Common Eastern Bumble Bee (Bombus impatiens). This species appears to fly quite late into the fall, with BugGuide having records as late as November for Ontario. It’s also very common, and not at all picky in its habitat or food plant selection. Anywhere and everywhere will do for these guys.

I don’t know about this one. It looks different from #2 – the blacks look blacker, the spot on the thorax larger, a wider band of yellow on the abdomen – but it could simply be individual variation. Or, it could be a male Red-belted, which show no red belt (just black). I think I’m leaning toward Common Eastern, however… it seems like it has a black head, whereas Red-belted would be yellow, I think.

The only other bee visiting the broccoli flowers was this little green sweat bee. There are three genera, all with shiny green representatives, and all looking fairly similar. This individual might be Augochlora… or then again, it might be Augochlorella or Augochloropsis…

This one looks like a bee, but is actually a fly (note the big eyes that touch each other). There are a number of species of flies that are bee or wasp mimics, their disguise providing them with protection against possible predators. Some are incredibly convincing. This one looks to be a member of the genus Eristalis, a group whose larvae are aquatic scavengers.

I was watching another fly when I noticed one of these guys camouflaged against the stem. A green caterpillar, so well hidden it had taken me several minutes before I noticed one. Looking more closely, I ended up spotting half a dozen. There are three species of green caterpillar that might be found on brassicas such as broccoli, but this one, with the thin yellow stripe, will become a Cabbage White butterfly, a very common species.

As I investigated, I spotted one caterpillar who was receiving some special attention from a little fly. It took a bit of hunting, but I believe the double-bulbed abdomen makes this a black scavenger fly, a member of the family Sepsidae, and probably within the genus Sepsis. Google “sepsis fly” and you get quite a number of results of studies looking at copulatory behaviour in the genus… From what I can tell, however, the family are more interested in dead than live material for laying their eggs on/in, and so this guy may not have had any real interest in the caterpillar after all.

Then there was this little wee guy. This one really is a species of ichneumonid wasp, and really is parasite of other insects. There are quite a number of species of ichneumonids, and I’m not precisely sure which this might be. I suspect, however, Hover Fly Parasite (Diplazon laetatorius), based on the black body and red legs with white stripes. It’s a widespread species that parasitizes the larvae of a wide variety of fly species.

These hemipterans weren’t new for me, though I had to look up their names again. Tarnished Plant Bugs (Lygus lineolaris), or perhaps a related species. It’s a fairly widespread species in the east, and adults are active most of the year, into quite late in the fall. Their larvae are generalists, but particularly like agricultural and commercial crops such as soybean and cotton (and, apparently, broccoli).

And the final critter crawling about the flowers was this tiny moth. It’s a Diamond-back Moth (Plutella xylostella), an introduced species that was probably accidentally imported in the mid-1800s. Caterpillars feed on plants in the family Cruciferae which – you guessed it – includes broccoli. Unsurprisingly, adults occur wherever these crop plants are grown (pretty much everywhere), and have a very long flight season.

Sunday Snapshots: Dog in a field

Extending the feeding season

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!

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.

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.