invertebrates – Page 27 – Seabrooke Leckie

Flight of the queens

Yesterday while taking the puppy out for her hourly bathroom break, I happened to notice a few swarms of insects crawling among the grass on the lawn. Closer inspection revealed them to be ants. They were reasonably contained to a small area, perhaps a foot square, for each swarm, and there were at least three or four that I noticed. They seemed to be mixed individuals, half small yellow-orange ones, and half larger reddish ones with wings. Sprinkled among them were a number of small black ones with wings.

It was the makings of a reproductive flight, and the participants are most likely of the genus Acanthomyops*. Late in the summer, on a warm, humid day, often just after a rain, these ant colonies send forth their reproductive individuals to fly, mate, and establish new colonies. The little yellow individuals are workers. They won’t be going anywhere; once all the excitement is over they’ll return to the nest and get back to business. The larger ones, though, with the big clear wings, are the new queens, and the little winged black guys are the males.

*Myrmecos comments to suggest the ants are Lasius claviger, which used to be Acanthomyops but scientific evidence showed that the species actually belonged to the closely related sister species Lasius.

They have evolved this strategy of all swarming at once for two primary reasons. The first is that if everyone comes out at once it makes it a heck of a lot easier to find a mate. Just within our little lawn there were several colonies producing reproductives that afternoon. The other reason is the whole safety in numbers premise – if everyone comes out at once, it’s impossible for predators to get everyone, so some individuals will survive to start a new colony. These swarms are sure an impressive and intriguing sight, it’s easy to sit for a while and watch them all crawling up and around and over.

Curiously, when I was looking up on BugGuide.net for more info on the genus (they don’t offer much, unfortunately), I discovered this photo of the same sort of Acanthomyops ant swarm, which was also taken yesterday. The photo was from Connecticut, which presumably had shared similar weather patterns to us here. I wonder just how many colonies were swarming yesterday afternoon?

The common name for ants of this genus is Citronella Ants, for the smell they emit when disturbed or crushed. I didn’t know this when I was looking for them, so didn’t check, but wasn’t likely to stick my hand in there anyway. They don’t have the formic acid defense that the most common household ants we encounter do, but I didn’t know that at the time. Another name they’re known by is Foundation Ants, for their habit of nesting in the loose soil that frequently surrounds the foundation of suburban houses. Unlike carpenter ants, however, they are harmless and don’t do any damage to the house, nor do they tend to forage inside.

The queens head for tall objects sticking up from the ground, such as twigs or blades of grass, from which they take off on their flight in search of a mate. Once they’ve found a male and mated, they’ll drop to the ground and look for a suitable, uninhabited location to start a new nest. The soft soil around foundations is easy for the young queens to dig in, which is why it’s so often favoured. Once the queen finds a spot she’ll drop her wings and start excavating her new home. It’s a lot of work, and will take her a while to establish. Many nests never make it past this stage.

Some species of ant, including Acanthomyops latipes (I don’t know if these are that species, or a different species of Acanthomyops), will avoid having to go through all that work by instead searching out a colony of the closely related genus Lasius. She’ll invade the colony, kill the Lasius queen, and take over control of the existing workers while she breeds a new colony of her own offspring. This behaviour is called temporary social parasitism. In fact, because of this close relationship between these two genera (as well as other reasons), Acanthomyops is sometimes considered a subgenus of Lasius, rather than a separate genus in its own right.

This little male looks tiny next to the large queens. The males, unlike the queens, will retain their wings till death, but that’s not all that far away. The male’s sole purpose appears simply to mate with new queens, after which he dies. While queens may be produced by young colonies, males are apparently only produced from older, mature colonies. A colony may last for many, many years, depending on the species. A queen will live for several years herself (up to 15 years depending on the species), but for older colonies it may not be the original queen present; rather, she may have died and been replaced by a daughter.

Not sure what this worker is doing. In fact, I’m not sure why the workers were out amid the swarm of winged reproductives period. I didn’t spend a lot of time watching them, because I had a rambunctious puppy at the end of the leash who didn’t have the same appreciation for such phenomena. I put her in her crate so I could take a number of photos of the colony, but couldn’t leave her there long. When I returned to the area this afternoon they were all gone, the area was empty. It’s amazing how fleeting it is, and you really need to be in the right place at the right time to notice it. Presumably a number of those queens I saw yesterday are now off starting a new nest of their own.

International Rock-flipping Day

Today was the second annual official International Rock-flipping Day, which I first mentioned back in this post. Dave at Via Negativa has begun collecting the posts by people who have participated and compiling them at this post on his blog.

I headed out just after noon, after temperatures had warmed up a bit. Rocks are in no shortage at our house. I started with a few up by the house, not finding a whole lot. A few millipedes (which are everywhere, a couple earthworms, including one giant fat one, and a cricket. The most interesting thing under these rocks was what appeared to me to be a beetle larva of some sort. After flipping through the beetle section of the Kaufman guide to insects, I’ve changed my mind, and now think it’s a rove beetle, possibly Platydracus maculosus, a widely-distributed, decay-feeding, short-wing-covered (but deceptively long-winged) beetle. I love the woodgrain patterns in it.

I headed down the hill, flipping a couple rocks in the forest. I expected a bit more from the forest rocks, since the forest always seems like such a rich habitat. You’d think there’d be lots of stuff munching on the deliciously rich detritus layer of the forest floor. But the rocks in the forest area were decidedly empty. The only really interesting thing was the below… white thing. It looked like it was probably a type of millipede, but it was very pale, paler than any millipede I’d ever seen.

I carried on and found this promising looking rock, above, sitting beside the base of a tree, near the forest edge and not far from the water. Indeed, when I flipped it over it had much more under it than any of the rocks I’d checked to that point. First thing I saw as a largeish spider, mouse brown with interesting darker markings. Again, no idea what it was. You know, the primary thing I learned about this whole exercise was how little I knew about most invertebrates. Particularly the rock-dwelling sort.

In there with the spider was the above slug. Apparently there are several types of slugs, and many of the most common ones are introduced. Who knew? This could be an introduced slug. It could also be a perfectly natural native slug. I have no idea. My guidebooks don’t do slugs. The most interesting thing under that rock wasn’t the spider or slug, but rather what looked a bit like a fungal garden of an ant colony. Aside from the fact that I didn’t see any ants, except one that ducked into the large hole in the ground. But all the tunnels that weaved in and out of the surface were suggestive of an ant colony, and the fungus looked like it was associated with it. It could have been complete coincidence, of course. Either way, it was an interesting rusty colour.

The best was saved for last. I ended up at the edge of the lake, where a portion of our shoreline is built up with large rocks. I flipped a couple of small ones, with no notable findings, before landing on a nice large, flat slab, resting on a sandy base. The treasure trove, such as it was, laid under here.

Although I’d seen a couple others under earlier rocks, there was a nice big, grey isopod under this rock. Which sat there quite obligingly, not something most will do for me. These aren’t insects, but rather are crustaceans. They like damp places, so are often found in basements or bathrooms as well. I bet you didn’t know that the extremely common pillbugs (without tails), and sowbugs (with two “tails”) such as the above, are all introduced from the Old World.

This beetle went scurrying before I could get a good picture. Darkling beetle of some sort, maybe? Or possibly a ground beetle such as Pterostichus sp.? It’s too bad I didn’t get a better photo, but then – I’m not sure it would’ve done me a whole lot of good anyway. There are so many beetles (Kaufman dedicates 90 pages to the group) and I don’t know enough about them to be able to differentiate between species that have similar shape and colouration.

Likewise, I didn’t get the best photo of this one, either. They move so fast! And you’re hoisting the rock up with one hand while scrambling to get the camera positioned with the other. I thought at first the shape of this one suggested tiger beetle, but I don’t think the head is big enough, and it doesn’t have spots. Now I’m thinking a type of ground beetle (it helps that it was fittingly found on the ground), perhaps an Agonum sp. such as Agonum cupripenne? This one has the look of iridescent-purple wing covers and an iridescent-green thorax, which the A. cupripenne images on BugGuide.net show. However, there are over 50 species in this genus in the northeast.

And lastly, my favourite bug of the whole outing. Also scurrying for cover, its wing covers spattered with droplets of water. Rain, perhaps, since it was raining lightly, briefly, before I stepped out. I’m fairly confident in calling this one a Bombardier Beetle, of the genus Brachinus. The members of this genus have the fascinating ability to spurt boiling hot liquid chemical from its abdomen, scalding the potential predator so the beetle can make its escape. It accomplishes this by combining two liquids (hydrogen peroxide and hydroquinone), contained in separate compartments in its abdomen, as it shoots them out at the threat. The liquids undergo a chemical reaction with the aid of a catalytic enzyme (an enzyme that acts to initiate or speed up the reaction), and rapidly reach a temperature of 100oC (212oF). In addition to scalding the skin, the chemicals can also stain it yellow. The species in this genus all look very similar – black wing covers, orange thorax and head – such that I have no idea which particular species this is. There’s 40 to 50 species in North America, usually found under things, like rocks, in damp areas at the edges of floodplains or water bodies.

And that wraps up IRFD 2008. Don’t forget to check out the official page for other posts!

Not-quite-a-thousand feet

We’ve had some “trouble” with critters invading the house here; I put trouble in quotations because although they are more than just the odd bug here or there, they’re generally (except the mosquitoes) not going to eat much, and so I cheerfully tolerate them. They’ve mostly been invertebrates of one sort or another, although we have had a chipmunk come to visit a few times as I’ve left the front door standing open for extra light and air circulation and he’s snuck in while my back was turned (I’m sitting typing away at my computer and hear something playing with the knobs on the ends of the drawstrings for the blinds). When the front porch light is on in the evenings it can draw quite a collection of insects, not just moths, and opening the door to go in and out often draws them in with you.

The ones that I haven’t figured out where they come from, though, are the millipedes. I suppose they, like the chipmunk, could also make their way in through the open door while my back is turned, though they always turn up at weird times of the day, and in weird spots. I’ll be going to refill my drink from the kitchen, and there’ll be one trundling across the middle of the kitchen floor. Or in the entry hall (that we rarely use) or in various corners. They all seem to stay downstairs, though, I have yet to see one upstairs. The one in the photo above was properly outside, on the deck. Millipedes curl up like this, with their head tucked safely in the centre, for protection against the threat of predators. It’s a characteristic of the group, and yet, virtually all of these guys that I’ve picked up have refused to curl up, instead waving their head about to show their displeasure.

I probably wouldn’t have noticed them at all or paid them much attention if it weren’t for their size. These millipedes are enormous. They’re members of the species Narceus annularis (closely related to and hard to tell apart from N. americanus, but Bev of Burning Silo, also a resident of eastern Ontario, indicates the former species is the one found here), which I’ve seen referred to on some websites as the American Giant Millipede. They’re not kidding with that label. The one in the photo above, while a larger individual, is not by any means the largest I’ve encountered here; the biggest ones can be as long as from the tip of my middle finger to the deep crease that crosses the middle of the palm of my moderately-sized woman’s hands. You would expect to find invertebrates of this size under the rocks of the tropical forests or in the tombs of the sort that Harrison Ford frequents from time to time, but it seems out of place in the middle of the temperate forests of eastern North America.

In fact, this species is wide-ranging and relatively abundant. It’s found through much of the east, from Florida north into Ontario, and west as far as Texas. They generally inhabit moist deciduous forest floors, munching on decomposing leaf litter and other detritus, though Bev also suggests, based on her own observations, that they may also forage on wet mosses or dead animals. In any case, their mouthparts are designed for chewing on soft materials, and they are therefore incapable of biting.

It’s funny, but despite the wide range, it’s another one of those species, like the Common Loon, that I tend to think of as “northern”. My parents’ place, while a patchwork of trees and swamp and scrubby area itself, contains a little deciduous forest, and is surrounded by quite a bit more, including huge swaths that make up portions of the Bruce Trail (which incidentally happens to pass right by their front door – handy for enterprising young children who want to make a few bucks selling fresh apples to hikers). I can see no reason, based on the habitat descriptions I’ve read, why these millipedes wouldn’t be found at my parents’ place also, but they’re not. The only places I’ve encountered them have been at a friend’s cottage, and now here, both at more northern latitudes.

They’re nocturnal foragers, and although I do encounter some during the day as they cross open spaces from one pile of leaves to another, I’ve seen the most, and certainly the largest, at night. As part of mothing activities I’ve spread a sweet mixture onto the trunks of a few trees to try to draw in nectar-feeding moths. So far all I’ve really succeeded in drawing in were a few earwigs – and dozens of millipedes. Even though it doesn’t seem much like their usual fare of decomposing organic materials, perhaps the smell of something fermenting (beer and a mushed-up banana are part of the mixture’s recipe) appeals to them.

They’re around all year, spending the winter buried under logs and bark, and coming out in the spring once it warms up. For most of the warm months they generally stick to the leaf litter, perhaps now and then crossing a trail or otherwise exposing themselves as they move from one place to another. However, they become increasingly easy to see during the months of August and September – that is, now, which is perhaps why I’ve seen so many since moving here. And this is why: these are the months where they start to get amorous and look toward increasing the population. As I went about checking the moth mixture for any actual moths, I discovered these two, tightly entwined in love’s embrace – or whatever passes for love to a millipede. I snapped a few shots but didn’t stop to ask.

Both male and female have internal structures called gonopores on their 3rd body segment (the first being the head) where the eggs and sperm are created.The legs on 7th segment of the male (the larger of the two here; you can see the gap in his legs created by the shortened 6th set of legs, on his 7th segment, actually clearer on the original photo) are modified into mating appendages called gonopods (gono, of course from the same root as gonads, and pods, meaning feet) that the male uses to guide the spermatophore to the appropriate location. To transfer the spermatophore to his 6th set of legs the male curls his head down to his body so he can reach. The female has normal legs on her 7th segment, since she’s not guiding sperm anywhere, at least not externally.

Females make an underground nest that they line with what’s effectively millipede poop, using the folds on their “tail” segment to smooth it into shape. They lay their eggs in this chamber, usually a few hundred. The eggs hatch and, depending on the species, the larvae may remain in the nest for up to the first three instars (growth stages as separated by skin-sheddings).

This one seems to be a female, having just normal legs on its seventh segment.

Check out all those little legs. Every one of the millipede’s body segments have two pairs of legs, with the exception of the head and “tail” segments, and the first four behind the head, which have just a single pair of legs each. Despite their name, millipedes never have a thousand legs; even the species with the most numerous appendages top out at “just” 750. On average for this species is maybe somewhere around a couple hundred.

I counted up the segments on this individual that I found; it has 49 segments with two pairs of legs each, and four segments with one pair of legs each, for a total of 102 pairs of legs, or 204 legs total. And I have trouble just coordinating my two sometimes! They move their legs in the same way an earthworm moves its body, with undulating waves of footsteps that you can sort of get an inkling of from the photo of the one on my palm.

They have eyes that resemble the compound eyes of flies and other insects, but are really just simply flat-plated occelli arranged into a group. Different species have different numbers of occelli; I did a quick count and this one seems to have about 35. The eyes aren’t good for much more than sensing light and dark, and perhaps basic shadows, they can’t detect shape or detail like an insect’s compound eye. Millipedes also have short little antennae that they use for sensing their immediate surroundings, and, in some species, possibly detecting the pheromones of the opposite sex, as well.

You can’t really see it well in any of the photos I have here, although if you look closely at the ones mating you can sort of detect it, but along their sides millipedes have small little breathing holes called spiracles. They use these as nostrils of sorts, but some species will also exude a noxious substance containing hydrogen cyanide, which can burn and discolour the skin, an effective defense against most predators. Supposedly (I found out after the fact) Narceus sp. are among this group of species, but of all the ones I’ve handled, not one has secreted anything, noxious or not.

Like all hard invertebrates, millipedes wear their skeleton on the outside – it has the appropriate name of exoskeleton. This is the main reason insects shed their skins as they grow, they don’t have the means for the skeleton to grow along with the body, so when things start getting tight inside, they ditch the old skeleton and form a new one. Millipedes add a few extra segments (and therefore extra legs) with each successive moult. I found this shed exoskeleton (or possibly the empty skeleton of a dead individual) when I rolled over a log in my hunt for millipedes to photograph.

Millipedes are an ancient group of organisms, with the oldest fossils dating back some 420 million years, almost twice as long ago as the earliest dinosaurs. There are an estimated 80,000 species of millipede in the world today, of which only 10,000 or so have been described by science. Of these, about 1,400 are found in North America north of Mexico. There are 14 species of Narceus, all found east of the Rocky Mountains, and most in the southeastern part of the continent. Up here in Ontario we seem to have just the one, N. annularis, with N. americanus found in other parts of the northeast. Still, with something this big, one is really all you need.

Arrival of the dog-days

I’ve noticed a couple of these old, empty husks clinging to vegetation at our new home over the last week. They’re the empty exoskeletons of cicadas that have metamorphosed into adults. Cicadas are somewhat grotesque, as bugs go, with large eyeballs set wide on a broad head, a thick thorax and abdomen, and large, clear wings with strong veination. These larval exoskeletons are even more so. Despite their appearance, however, cicadas are harmless to humans, and they have no interest in crops so aren’t considered a commercial pest, either.

Mostly they’re just loud. They’re the insects that make the long, sustained buzz that we tend to associate with the hot, dry, and sunny days at the height of summer. When you’re close to the cicada while it’s making this noise the sound can be as much as 120 dB – that’s louder than a jackhammer! Only the males make the noise. Most insects, like crickets, make noise by rubbing two body parts together, often the hind legs or wings. Cicadas are different in that they use a built-in mechanism to make noise. They have a set of tympanic membranes on the sides of their abdomens called “tymbals”. The tymbals have muscles that connect to their inner surface that pull the membrane inwards when they contract. This produces a clicking sound. As the muscle is relaxed and the membrane returns to its normal position, another click is heard. By doing this extremely fast and many times over, the cicada produces the buzz we associate with them. The male’s abdomen is also mostly hollow, which acts as a resonating chamber to increase the volume of the sound. Cicadas “hear” through a membrane mechanism much like a frog’s ears, which could be damaged by the loud noise he makes with his abdominal tymbals, so the male “turns them off” while he’s calling.

There are two types of cicadas. The most famous are the periodical cicadas, the ones that are on 17- or 13-year cycles and come out en masse in huge swarms in a single summer. This strategy developed to make it difficult for a predator to specialize on the adults of the species; since both 13 and 17 are prime numbers, a predator specialist would also have to be on a 13 or 17 year cycle (if the cicadas were on a 15-year cycle, for instance, a 5-year cycle predator could sync up with them easily).

The other cicada species have much shorter life cycles, usually between two and five years, and adults are present every year, giving them the name annual cicadas. Despite that I would have to have lived through at least one periodical cicada emergence, I’ve never observed it firsthand. Annual ciciadas, on the other hand, I’ve observed regularly. As I was returning to the house from the dock this morning I happened to come across this one, still in larval stage, climbing up the side of a tarp.

He looked like he’d come straight out of the sand. Cicadas spend virtually all of their lives underground. The adult females lay their eggs in the twigs and branches of trees, and the larvae, once they hatch, drop to the ground and burrow into the soil. They feed on the sap from the roots of the trees. Their front legs are broad and strong, adapted for digging, with well-developed hooks on the ends.

After several years the larval cicada finally reaches a size where it’s ready to metamorphose. It climbs out of the dirt and up onto a plant or the trunk of a tree. In the case of the cicada I found, it had decided the tarp provided a suitable substrate. The cicada sets its hooked feet firmly, then splits open the skin on the back of the head and thorax and pushes its way out. Cicadas undergo incomplete metamorphosis, meaning that they don’t have a pupal stage the way butterflies and many other insects do. Instead, they go directly from their final larval stage to the adult, crawling out of their skin in their final adult form. It comes out pale; as the insect’s exoskeleton hardens, it will darken. The adult will eventually be olive green and black.

I figured that this one was looking to find a spot to metamorphose, and I was right. I sat down and watched most of the insect’s emergence. When it was mostly out it sat and recovered some energy for a while. It stayed in that position for at least 15 minutes; when I eventually decided that it wasn’t going to be doing anything imminently I went inside to get lunch started, as Blackburnian and I had plans to go out this afternoon. I check on it once while waiting for one side of a grilled cheese sandwich to brown, and it hadn’t moved. However, in the space of time it took to butter another sandwich and put it in the frying pan, the cicada had emerged completely and unfurled its wings.

It was an interesting process to watch, because I could see the insect, while still in its larval skin, shifting to make sure its claws were firmly dug into the substrate, and then appearing to apply pressure to its back to split the skin. Once it was starting to emerge I could see it working to pump haemolymph, the insect’s equivalent to blood, into the soft wings and body parts. It would have been neat to capture some of it on video, or to take a time-lapse series of the process.

However, I did my best to get a series of photos of the emergence of the cicada, start to finish. Photos below of the process. You can see in a few of them the long, tube-like piercer the insect uses to suck sap from trees. I believe this is a Dog-day Cicada, Tibicen canicularis.

And all that’s left is the empty shell.

So I guess if the Dog-day Cicadas are emerging, that means the dog days of summer must be officially arrived.

Construction workers

My parents’ house is an old century farmhouse, onto which a three-room addition was built. Two rooms are on the same level, but the one at the back is slightly raised, and the roof is at a shallower pitch. Where the two meet there’s a slight overhang, which has been edged with the same trim that runs along the front of the house. For the last few weeks, there have been small piles of sawdust collecting on the shingles under the eaves of the house here. In rainstorms they all get washed away, but in short time they have returned.

There are actually termites in Ontario, and they have been reported from Halton County where my parents currently reside. However, termites tend to be subterranean creatures, building tunnels on the surface of objects (such as walls) when they want to move someplace. While termites might be the creature that immediately jumps to mind at seeing such evidence, sawdust observed so high off the ground and without any apparent tunnels most likely belong to another culprit.

I climbed up onto the roof while I was painting that bit of the exterior wall, and got a second clue. From the bit of trim above the sawdust piles, I could hear very distinct, very loud chewing. Because of the way the roof slopes I could look up and under the eaves and see if I could spot whatever it was, expecting a vertebrate of some sort, but nothing was there. Annoyingly, while I was trying to check things out, and then later as I was painting, a bumblebee kept coming up and hovering around me. I’d back off and let him disappear and then continue on.

I overlooked the most important clue: the bumblebee. Which, it turned out, was not a bumblebee at all. I came home and looked up bumblebees. They are all generally solitary insects, nesting underground. I had this vague notion of “carpenter bee”; I knew carpenter ants, carpenter beetles… I googled Carpenter Bee anyway. The very first webpage that came up, an information page at Penn State, started out by saying, “People who complain about bumblebees flying about under the eaves of their homes are probably being annoyed by carpenter bees.”

Well. Mystery solved. Here in eastern North America, the species we have are Eastern Carpenter Bees, Xylocopa virginica. They are large, chunky, bumblebee-sized bees that are also marked in black and yellow fuzz. The primary visual difference is that bumblebees always have fuzzy abdomens with a bit of yellow, while carpenter bees have completely black, fuzz-less abdomens. Of course, I didn’t know this at the time. I also think I had at some point learned that bumblebees nested underground, but was forgetting that at the time. Bumblebees will generally have no interest whatsoever with your eaves.

Carpenter bees, on the other hand, are very fond of eaves. Or really, dead, unpainted wood in general. Carpenter bees, as the name implies, will construct their nest burrows in dead wood. In the wild they would ordinarily do this in snags, dead branches or fallen logs, on the underside or the lee side of the wood. However, they’re not especially picky about the wood they use, and the processed wood we humans use to build our homes and outbuildings, as well as fence posts and boards and other outdoor constructions, will suit them just fine. If you want to make sure the bees don’t target your buildings, make sure they’re all varnished or painted, which generally discourages them.

Females do all the nest-building. The individual in the photo above is a female; she can be told by her longer, pointy abdomen and her all-black face (males have a splash of yellow across their forehead). Females also have larger heads with more widely-spaced compound eyes (those of a male come close to touching at the top). Females use their powerful mandibles to carve out the tunnels. She looks like she might be holding a wood chip from her tunnel in the photo above.

They start out with a hole approximately 1 cm (less than half an inch) wide, building straight in to the wood for an inch or so, usually against the grain, and then make a right turn and build the rest out perpendicular to the entry tunnel, this time with the grain. They generally prefer wood that’s at least two inches thick, so the 1×8 boards that formed the trim on the eaves didn’t actually present a very thick tunneling substrate.

The tunnel will end up being 4 to 6 inches (10-15 cm) long when completed, and it takes a female on average about 6 days to complete an inch of tunnel, which means anywhere from 30 to 42 days to do the whole thing. She pretty much spends her whole life focused on that activity, and when she’s done and has laid her eggs, she’ll die.

Once the tunnel is complete, she’ll systematically start filling it with future bees. She’ll begin by forming a ball of pollen and regurgitated nectar and placing it at the end of the tunnel. She’ll lay an egg on the ball, then seal it off into its own compartment using chewed wood pulp to form the barrier (perhaps that’s what she’s carrying that woodchip for in the photo). She’ll form 6 to 8 compartments within the tunnel, each with a single egg. This is a lot of work for just 8 offspring, not all of which will survive to adulthood and reproduction age.

Carpenter bees are not truly social bees, the way honeybees are; every female has the potential to reproduce, and there’s no queen organizing the group. Each female will build her own tunnel. However, they will often congregate in the same general area. This is partially because a female will tend to reuse the nest she hatched from, or build her new nest nearby. A single board can be targeted and eventually become riddled with nests while other boards may be left untouched. In cases where these holes are excavated in a structural beam they may cause concern, but generally speaking carpenter bee damage is mostly cosmetic.

From the laying of the egg to the emerging of the adult takes about seven weeks, though the timeframe may be longer or shorter depending on local temperatures through that period. The adult will emerge from the chamber where it developed by chewing its way out through the partitions along the long tunnel to the entrance. Adults will generally emerge in mid- to late-August, and will spend the rest of the summer and fall feeding on nectar from flowers (an interesting habit they have is to not always go through the mouth of the flower, but instead sometimes pierce the base of the flower to get at the nectar without pollinating it).

In the fall they’ll return to the tunnel where they hatched from, and they’ll spend the winter there. In the spring they’ll emerge, and the females will start building their tunnels. The males, while the female is hard at work, will patrol the area. Males are harmless, as they have no stinger and cannot sting, but they are curious and may come over to check you out if you wander into their area, which can be very disconcerting. Females do have a stinger and are capable of stinging, but are generally fairly docile, ignoring you if you’re just simply in the area, and will only sting if handled.

When I went up to paint the walls on other side of the house, I discovered this scene underneath the eaves. It looked like the half-developed contents of one of the tunnels had been pulled out by something. Scattered on the shingles were a few chunky larvae, one of which that looked like it was halfway into turning into a pupa, as well as some thick orange chunks. I’m not sure what the orange chunks are, but I suppose them to be the pollen balls that the larval grubs are provisioned with.

I have no idea why these were all on the shingles. If it had been a predator one would think that the grubs would have been eaten, not left to roast on the hot roof. It takes the adult female about a day to provision and seal off each cell, so I was wondering if perhaps the egg that had been laid first had already pupated and emerged as an adult, and as it chewed its way through to exit the tunnel it ended up knocking all the others out. But that seems a bit of a stretch. Maybe a rival female went in and pulled everything out so she could use the tunnel? Also seems a bit of a stretch. I couldn’t find anything online to suggest the reason for it.

The book Insects, by Stephen Marshall, indicates that Eastern Carpenter Bees used to be more restricted to the United States, but in recent decades have been moving north into southern Ontario. Given their strong site fidelity I’m not sure how quickly they spread, or why they would be moving north. However, this may explain why this is the first year we’ve noticed their presence there. They sure seem to like the spot now that they’ve found it!

Carpenter bees are, like most bees, important pollinators in an ecosystem, and many people will tolerate their presence in their buildings despite the damage because they provide a valuable services to their flowers and trees. Unfortunately, pollinators the world over are in decline due to habitat loss and widespread pesticide use, as well as other pressures. A group called Pollination Canada runs a citizen science project where you can make observations on your local pollinators that will help scientists to better understand what’s going on with this very important group of insects.