invertebrates – Page 7 – Seabrooke Leckie

Snow fleas

I usually try to make a point of not repeating myself too much here on the blog. Unless I have something new to add to what I’ve said before, I’ll normally avoid posting about something again. I’ll make an exception for snow fleas. Ever since I discovered them last winter, I find myself inordinately pleased to spot some during my hiking. I’m not sure why; they’re not (it turns out) uncommon, nor are they particularly special to look at. But something about them just tickles my toes.

I saw my first snow fleas this weekend, on a “balmy” afternoon where the sun had been out for a bit and the temperature had climbed to reach the freezing point (0/32). Most likely they’d already been out and about for a while, and it just took me this long to pay attention. It’s not as though they jump out at you, exactly. In the photo above, for instance, I counted about 60. But they’re a very underwhelming 60, and one could be forgiven for thinking they were simply specks of dirt, debris, or maybe little grass seeds that had scattered on the snow.

They usually move about in groups, however, which tends to make spotting them easier. One tiny speck is easy to overlook; dozens of tiny specks might actually be something interesting. If you peer close enough, you can see the tiny legs and antennae that identify them as invertebrates and not scattered seeds.

A few interesting facts about springtails:

They’re not actually insects, but are part of a sister class to insects, the Entognatha.
They’re the only six-legged critters to be found wandering about Antarctica of their own accord.
They prevent themselves from freezing through a special antifreeze protein in their blood, which is being investigated for use in extending the transit life of transplant organs.
No one seems to know what they’re doing on the snow in the winter. One hypothesis is that they feed on algae that grows on the snow or on tree trunks.

More info recounted in last year’s post, if you’re interested.

Fir galls

Continuing with the theme of the left-behind… I do a lot of peering at branches in the winter months, after most life has gone into hiding. Sometimes some interesting discoveries can be made, affixed to (or even within) twigs or branches. I took Raven down to the 100-acre Woods yesterday, the first time we’ve gone in a little while because of hunting season (we’re in the mid-November hunting lull at the moment, but we wore our brightly-coloured jackets, just to be safe; I don’t think anyone hunts on that bit of land, but who knows what goes on there when no one’s around to see it). The forest has a fair bit of Balsam Fir scattered through the damper areas, and I paused at one clump to finger the needles, whereupon I noticed these odd little lumps amidst the foliage. There were a lot of them, mostly at the outer ends of the branches, and mostly (it seemed) on the east side of the tree (though that might just be coincidence).

Determining their identity was fairly easy once home. A Google image search for “balsam fir needle galls” turned up several pages with identical galls to mine. Gotta love the forestry industry’s thoroughness; virtually anything you want to know about pests of commercially valuable tree species is available online. The pest in question here is a tiny midge, Paradiplosis tumifex, which goes by the appropriate English name Balsam Gall Midge.

Eggs are laid on current-year needles as they’re growing (which explains why the galls seemed mostly to be near the ends of branches), and when the egg hatches the larvae burrow into the needle to settle down and feed. The needle forms a gall around the larva and its new home. The larva eats and grows and eats and grows, until mid-autumn when they finally break loose of their gall and drop to the ground. There, they burrow into the soil under the tree and wait for spring. Warming ground temperatures in late April and early May encourage the larvae to pupate, and a week or two later the tiny adults begin to emerge. Females mate, then return to the newly-forming fir needles where they lay their eggs, and the cycle begins again.

Once the larvae leave the needles in the fall, the needles brown and drop from the tree. The branches were scattered with the ones that had caught in the twigs. I noticed on the ones that were still attached to the branch that a few of them seem to be broken off; I’m not sure if this was from the midge larva emerging, or environmental damage post-emergence. The midges are no more than a nuisance, apparently; they do no long-term damage to the tree, beyond perhaps mildly stunted growth that year when under severe outbreak conditions. The galls are dropped by the winter, and even aesthetically the tree looks fine again quickly (important for the Christmas Tree market). Populations are cyclical, with two or three years of high numbers, followed by several of low. I can’t remember having noticed anything unusual about this same tree last year (it grows beside the path), and I’m not sure if that’s because numbers were low last year and high this year, or I just wasn’t looking.

Monarch chrysalis

November seems to be the time of leftovers and left-behinds, as animals head south, or into hibernation, or otherwise start preparing for winter. November is when I start seeing the summer’s empty birds’ nests, old cocoons, empty shells of things. It’s probably in part because with the animal and plant life disappearing, the eye is drawn more to the inanimate.

I spend a lot of time staring at the ground in November, and so I was doing when I came across this. It was just a bit of curled up paper hidden in the grass, and I nearly dismissed it as a bit of birch bark before pausing for a better look. Stooping down, the bit of paper revealed itself to be an old, long-since-vacated chrysalis. Naturally, I’d left my camera back at the house on this particular outing, so I decided to break off the grass stems and bring it back.

Caterpillar silk is surprisingly strong. I broke off the two grass stems that the chrysalis was obviously attached to, and lifted gently, but there was still another. So I snipped that dead leaf and tugged again, and it was still affixed to something. I broke five bits of grass to finally be able to get it out, and a sixth was hanging by a thread of silk, which I sawed through with a fingernail. No surprise this stuff makes good clothing.

The light was waning when I got back to the house, but I ran off a series of shots. Even though the sides of the chrysalis are in tatters, enough of it remains intact that it’s easy to see the identity of its former occupant: The roundish top, the beaded ring a third of the way down (now lined with black), and the general size all clearly mark this as a Monarch chrysalis. While it housed a metamorphosing caterpillar, it would have been minty green, and that ring of beads was gold.

When I started taking photos, I was surprised by the pattern of black on the top, where it attached to the grass. The stem itself is called a cremaster, and is formed from the tail-end of the caterpillar just before it sheds its skin for the last time. The caterpillar makes a silk “button” then shoves this black rod into it in order to affix itself; once done, it hangs from its tail, curls into a J, and splits its skin along its back. For an amazing sequence of photos, strung into a video, of a Monarch caterpillar changing from caterpillar to chrysalis, you should check out this NPR page, a commentary by Julie Zickefoose. Julie’s also got some amazing transformation photographs at her own blog – here, here and here, for instance. Every year she brings in a couple of fifth-instar caterpillars so her family can watch them metamorphose from larvae to butterflies.

The outside of a chrysalis or pupa is effectively the sixth skin of the caterpillar (it’s already shed five, to get here), rather than an external structure such as the hairy cocoons moth caterpillars make. Because of this, many of the structures of the winged-adult-to-be are defined in its hard shell. With moth pupae, especially, it’s possible to see the shape of the wings and antennae of the adult moth. Butterfly chrysalids need to be more camouflaged and tend to show other shapes (or at least, I presume that’s the reason they show other shapes; they don’t have the same hairy cover that above-ground-pupating moths make).

But I did notice something else on this one: the spiracles that line the abdomen of the insect. Spiracles are the insect’s “nostrils”, the holes through which it breathes. All insects have them, but on many (most?) they’re well-hidden. I thought it was interesting that they were so prominently visible on this old shell; you can see them on the green chrysalis, too, but not as clearly.

And then the other interesting thing I discovered, while poking about BugGuide.net, was mentioned on this photo and this photo… Apparently you can sex the insect inside the chrysalis based on the presence or absence of a small line at the base of the string of black dots. I’ve indicated it in this photo using a yellow arrow. If the line is present, the insect is a female; if it’s absent, the butterfly is male.

This is the first Monarch chrysalis I’ve ever seen in the wild. It would have been more exciting if it had actually contained a Monarch at the time that I found it, but I still think it’s pretty cool!

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.

Canada Darner

A few days ago Dan pointed out a dragonfly that was sunning itself on the screening of the window at the front of the house. Or at least, it looked like it was sunning, on the south-facing side with its wings spread. Dragonflies (and all insects) being exothermic, most of their body temperature control is achieved through exposure (or not) to the sun (some insects will shiver, too – you may see this in moths, for instance, on cooler nights).

It didn’t move, though, and I began to think maybe it was dead, the barbed feet still clinging to its final resting place. It did look a bit ratty, with a few nicks out of the delicate wings. It didn’t leave as I approached, or even as I reached out to grasp it. But as I gently folded the wings together over its back there was stiffness, resistance, that wouldn’t be there if the insect was dead. Holding the wings firmly, I lightly pulled on it to see if it would hold on to the screen; it did, and the legs moved feebly once detached.

So it was still alive, just sluggish from the cool night. I took a few photos but left it where it was. Half an hour later, presumably sufficiently warmed, it had left.

The large size of this dragonfly makes it a darner, and the dark body with two diagonal stripes on the thorax makes it a mosaic darner, one of the species in the genus Aeshna. There are more than a dozen mosaic darner species in our area, and they all look confusingly similar. Identification is usually best made with the critter up close or in the hand, but they rarely settle down for long and are frustratingly difficult to catch with a net, while in flight or otherwise. The vast majority of my identifications of this group have been made in situations such as this – sluggish individuals that are easy to get a photo of.

The ID for these guys depends primarily on two characteristics: the shape and colour of the thoracic stripes, and the same of the markings on the abdomen (particularly the segments closest to the body). The eyes can also be useful for species identification. Having the dragonfly in-hand, or having a photo of it, while you ponder the possibilities is really invaluable because it offers you the opportunity to check for small details.

In the case of this one, it has a very distinctive marking that no other species have: that little dot just on the inside of the front thoracic stripe. Also, the sharp hook on the front of the stripe itself. Both of these features identify it fairly easily as a Canada Darner, Aeshna canadensis. The majority of the mosaic darners are not nearly so easily identified, bearing more generic straight slines of varying widths.

I have two dragonfly guides: Stokes’ Beginner’s Guide to Dragonflies and Dragonflies Through Binoculars. I like the photos better in the first, but the species coverage and information are better in the second. There are a few other regional guides in print, some of which are very good, that I simply haven’t gotten around to picking up. At this point, though, I’m waiting for the new Peterson Field Guide to North American Dragonflies by Ed Lam. I’m not certain when it comes out, but Ed was contracted in 2006 with a four-year submission target (I think), which would make it within the next year or so. Ed is painting every single species. Males and females and colour morphs. I can’t even imagine the amount of patience such a task would require! But the guide looks to be beautiful and extremely usable once it’s done. You can check out samples of the illustrations at his website.

Canada Darners are late fliers. They first start to emerge in July, but they can be found on the wing through October, till we get into sustained periods of cold. Some species of darners are migrants, moving south in the fall to warmer regions. Those great swarms of darners you might sometimes encounter during the late summer and autumn might be migrant swarms, feeding before they push on (darners will also simply swarm where there’s really good eats to be had, though, and it can be hard to determine which type a particular swarm is). However, Canada Darners, as far as I know, are not one of the migrating species.

Interestingly, Dragonflies Through Binoculars notes that “this species darkens when cool”. I gather this isn’t the case with all species of mosaics, and would explain why this individual looked so muddy to me. Those thoracic stripes are usually sky blue and yellow-green. The abdominal markings are generally all blue. You can just see the colours starting to come out in the thoracic stripes – if that is indeed what’s happening here – though the abdominal markings remain brownish.

Aside from this guy, the only other dragonflies I’ve seen around in a couple of weeks have been meadowhawks, which seem to be the latest fliers around here, at least in any numbers. Soon, even they’ll pack it in for the year. It’s nice to enjoy these lingering traces of summer while they last.