invertebrates – Page 25 – Seabrooke Leckie

Today at Kingsford – Blister beetle

Right. So the purpose of yesterday’s post and all those headstones wasn’t actually to ramble on about life and death, but actually to introduce this guy, who I stumbled across in the grass and pine needles among the stones as I was slowly meandering through the cemetery. Its gleaming blue sheen caught my eye as it crawled through the obstacles. I knew what it was, so I coaxed it onto an oak leaf and gingerly moved it to the top of a stump where I could get better photos.

It’s a blister beetle, in the genus Meloe (oil beetles). There are 22 species in the genus, but they’re difficult to tell apart. All but one occur only in North America. Blister beetles get their name from their characteristic of exuding a skin-blistering chemical when they’re squeezed or unduly disturbed, a behaviour called “reflex bleeding”. The chemical, cantharidin, is contained in their haemolymph, or blood, and is exuded from pores at their joints. Members of the genus are generally quite plump, and flightless, though they have shortened, residual wing-covers.

You’d think that would be interesting enough, but even more so is that individuals go through multiple larval life stages (not just instars, but actual different types of larva), more than the average insect, which is called “hypermetamorphosis”. Eggs are laid on vegetation, and when the larvae, called triungulins at this stage, hatch they crawl up flower stems to wait on flowers for a passing bee. They hitch a ride on a female bee when she comes around, and are taken back to the burrow she’s created for her own eggs and larva(e). There, the triungulin moults into a grub and sits and consumes the pollen and nectar that the female bee brings to provision her own larva, and then eat the bee’s larva itself once it hatches from its egg. Each Meloe species generally targets a single species of bee, and while it will eat the larva, it can, if necessary, survive just on the pollen and nectar and so doesn’t qualify as a true parasitoid.

BugGuide.net also adds, “In at least one Meloe species, the larvae climb to the top of a grass or weed stalk as a group, clump together in the shape of a female solitary ground bee, exude a scent that is the same as, or closely resembles, the pheromones of the female bee, and wait for a male ground bee to come along. When he does, he tries to mate with the clump of larvae, whereupon they individually clamp onto his hairs. He then flies away, finds and mates with one or several real female bees, and the larvae transfer to the female(s).”

I presume this to be a female, both because she’s exceptionally plump, but also because her antennae are straight. Males have little hooks in the middle of their antennae which they use to grasp the female when mating.

Among other uses for the blister beetle – the males of some beetle species “collect” the cantharidin from the blister beetles and use it to impress females, and then includes the chemical in the sperm packet that’s transferred to the female. When she lays her eggs, they’re coated in the chemical, which protects them from predators. The chemical has also been used by humans for centuries in the production of the aphrodisiac “Spanish Fly”, frequently used nowadays as a date rape drug.

Today at Kingsford – Marbled Orbweaver

I took Raven out for her regular walk this afternoon. I took my camera with me even though it was overcast and threatening to rain, since you never know what you might come across. Thank goodness I did, or I would’ve missed documenting this wild spider. It was walking across the road, and both its size and colour made it exceptionally eye-catching on the bare surface. It was huge. Its abdomen was about the size of my thumbnail. I have no idea why it was crawling across the road, but I couldn’t resist pausing to run off a series of photos.

Such a distinctive spider was pretty easy to ID. I already knew it was an orb weaver because of the giant abdomen, and shortened third legs. A search for “orange orb weaver” on BugGuide.net turned up a bunch of photos, including several of my critter. It’s a Marbled Orbweaver, Araneus marmoreus, a fairly common spider of woodland clearings and long-grassed meadows. It’s been recorded in all of the Canadian provinces, with the majority in the more open southern Ontario and prairie provinces. There aren’t many records from the US on that page (it is CanadianArachnology.org, after all), but BugGuide.net shows records for most of the eastern states. Worldwide, it’s a holarctic species, found in Eurasia as well.

Its abdomen is intricately patterned, almost looking like bubbles, but the thing that I thought was particularly neat is that the pattern is asymmetrical, especially right at the front. There’s actually two morphs of this species, this one (which can also come in yellowish versions with dark markings), and one whose abdomen is mostly pale with a large dark blotch at the back. The latter form is only found in Eurasia, and rarely overlaps in range with the orange version. How they know they’re the same species is a mystery of science. The large size makes this a female. Females can reach 14mm (body size minus the legs) while males are much smaller, reaching just 9mm. Being a member of the Araneus it ought to show a longitudinal crease down the abdomen (as opposed to Neoscona, which has horizontal creases), but if there were any creases at all, they weren’t visibly obvious to me.

All legs

Readers who have followed my blog for a while may have noticed I haven’t posted anything on moths in a couple of months. Part of this has been that there’s just been so much else to catch my interest I haven’t gotten back to them. However, part of it was also that I broke my one and only mercury vapour bulb shortly after moving in to the new house. The mercury vapour is a very bright bulb that projects light in the ultraviolet spectrum and draws moths in like crazy. Nothing else really compares. I tried running my trap with just a blacklight in it, but didn’t catch very much. It has been a bit of a headache trying to replace the bulb from out in the middle of nowhere. The first set of bulbs I bought off eBay turned out to have the old-style mogul screw base used in security lights (rather than the standard, smaller one that all household bulbs today have), which of course didn’t fit my trap. It took me another few weeks to remedy that situation, and another purchase off eBay to get converter sockets that make a mogul bulb fit a household base (would you believe Home Depot and Rona don’t carry these?). But they arrived this Wednesday – hurrah! – and I’ve run my trap the past couple nights. We’re well past the peak moth period, which is June and July, but there are still lots of interesting species flying right now.

This morning, in a rush to get ready to go out for a training session for Elections Canada (I signed up to work at one of the polls during the election next Tuesday), I only had time to turn off the light and move the trap around the corner where it’d be out of the sun. So I wasn’t really looking at much, and if this guy had been anywhere else other than smack in the middle of the beige siding, I probably wouldn’t have noticed him. But there he was, presumably drawn in to the light during the night.

It’s a stick insect, of course, a Northern Walkingstick (Diapheromera femorata). Walkingsticks belong to the order Phasmatodea, which contains some 3000 species, most of which are tropical in range. In North America there are 33 species, all of which, except one, are wingless. The Northern Walkingstick is found through most of eastern North America, from southern Canada south to Florida, and as far west as Arizona and Alberta. It’s usually found in hardwood or mixed forests, so it’s no surprise to see it here, given that the region is nearly one continuous hardwood forest.

These guys are amazing insects. They’re not commonly seen; in my three decades I could probably count the number I’ve seen in the wild on one hand, but it’s been so long since I’ve seen one that I don’t know how many digits I’d be able to put up. So I was doubly excited to find it, both for its cool factor and its apparent rarity (it’s not actually all that uncommon, but appears rare because one rarely sees one).

Many insects have evolved body structures that camouflage them, but the walkingsticks and stick insects have taken it to an extreme. Their bodies are thinner than pencil-thin, and the joints resemble the bumps on a twig. Their legs are tiny and delicate, and extremely long. While their body is brown, their legs are green, kind of like the leaf petioles or young sapling twigs that stem off a main twig. When at rest they often align their forelegs, and sometimes their back legs, straight out in line with their body as in the first photo, to increase their disguise. A few tropical species look like walking leaves, rather than twigs.

Although stick insects, like all insects, go through metamorphosis, theirs is a “simple” metamorphosis, where the larval and pupal stages have been dropped. Baby walkingsticks hatch from their eggs resembling miniature adults, only green, and simply grow bigger as they age by shedding their skin, eventually becoming brown. Grown adults are sexually dimorphic, with males being considerably smaller than females – males may reach 7.5 cm (3 inches), while females can grow to 9.5 cm (3.75 inches). Females have a more swollen look than males, and I suspect the twigginess of this individual makes it a male, but the pincers at the end of the abdomen confirm it (they’re used in mating).

Females of this species will lay their eggs in the leaf litter of the forest floor (BugGuide.net says they “drop eggs singly”.) In the spring these eggs hatch and the nymphs reach sexual maturity by late summer or early fall. There are a few species of walking stick that reproduce through parthenogenesis – that is, there are no males, and the females essentially lay eggs that are clones of themselves. Even more amazing, walkingsticks are often able to regenerate lost limbs during larval stages, something most insects are incapable of doing.

The walkingstick’s face looks much like just another knob on the end of the twig. Their entire body design is built around blending in with their surroundings. They feed primarily on the deciduous leaves of hardwood trees, particularly oak and hazelnut, also rose and apple. Nymphs apparently have a different dietary preference, favouring sassafras, raspberry, and black cherry. In years of high walkingstick abundance they have the ability to severely defoliate their food trees. Their simple dietary requirements make them an easy bug to keep and breed in captivity, where they may live to about a year old.

After posing the insect on a number of branches and trunks where he was easily seen, I placed him in the foliage of an aster, now nearly done blooming. This is where his camouflage really kicked in, and he all but disappeared into the plant. Walkingsticks are generally slow movers (as are the twigs they mimic), though they can really boot it when they want to (as I discovered while trying to move him from one spot to another). They sometimes sway gently as they move, hypothesized to either mimic swaying branches, or possibly aiding in their visual detection of their surroundings by differentiating close objects from the background (something characteristic of simple insects).

I left him resting in the aster, where he was well-hidden. Hopefully they’ll be a frequent sight around here! It does make me think back to a few small, thin, green little bugs that we had hanging around the house back in August and didn’t know what they were. I wonder if they could have been young walkingsticks?

Today at Kingsford

Something I’ve noticed since moving here is just how different the household fauna is from what my parents get in their house. This guy has spent the entire day on the wall of the entry hallway. Or actually, it might be a she, given the lack of noticeable pedipalps (modified mouthparts that resemble boxing gloves and are used by the male in transferring sperm to the female). She hasn’t moved much all day, perhaps about eight inches from the wall to the nearby door trim. A bright orange spider with a tan-coloured abdomen, I’m sure finding this in my parents’ place would have stuck in my mind.

This is an orb weaver spider, the sort that make those stereotypical spiderwebs that get drawn on Hallowe’en decorations. Orb weavers generally have large, rotund abdomens, and third legs that are shortened and modified for building and walking on their special webs. There are some 180 species of orb weaver north of Mexico, but few are readily identifiable to species without examination of the genitalia under a microscope. Most can be assigned to genus, though, and I think this may be a member of Neoscona, the Spotted Orbweavers. The genus Araneus is very similar, though, separated by the groove in the abdomen running lengthwise in the former, and crosswise across the abdomen in the latter, though it can sometimes be tricky to see without magnification. I’ve submitted it to BugGuide.net for ID, hopefully someone there will be able to ID it.

The gentle giant

I’ve been holding on to this subject for a little while, always having something else lined up or that I came across that I ended up talking about first, but I’ve been wanting to post it. Yesterday and today we had guests up, so I didn’t get a chance to take many other photos, which meant this was a great opportunity to sneak this one in.

Not long after our arrival here we started noticing these GIANT, MONSTEROUS wasps coming to the porch lights at night. So large, in fact, that wasp wasn’t the first insect that came to mind when we looked at them. It took me actually catching one, and chilling it in the fridge, to get a good look at it and confirm that it was, indeed, a wasp. A little nervous to even put my hand anywhere near the thing, I was very careful to take my photos quickly, while it was still sluggish from the fridge, and using a pencil for scale rather than my fingers like I often do.

My first thought was a cicada killer, a type of native wasp that is similarly giant. But the markings weren’t right for cicada killer (and I looked at quite a few pictures, feeling at a loss for whatever else it might be). Eventually it took doing a search on BugGuide.net for “giant wasp”. That turned up a good number of hits; cicada killers, of course, but also my wasp. Turned out, it’s a European Hornet (Vespa crabro), the largest species of the hornet family, and an introduced species, originally native to Eurasia. It was introduced to New York sometime around 1840, and has become well established in woodlands and forests through much of the east.

Fortunately, these hornets are a fairly peaceful species. Sure, they sting, as do all hornets, but it requires some specific provocation, they aren’t aggressive simply to one’s presence. This proved true as we would go out to check out the moths and other insects coming to the lights, none of the hornets ever seemed even the least bit interested in us, although their heavy, loud buzz was still a little off-putting. The hornets are attracted to artificial light on summer evenings, not unlike many species of ichnumonid wasps and sometimes other types of wasps as well. BugGuide.net suggests they may be seeking prey, but the ones I observed didn’t seem to show much interest in the other critters at the light.

The nests the wasps build is a one-time-use-only structure. They nest in hollow trees, or sometimes in attics, which are a decent approximation of a hollow tree if the real thing is not abundant. Like the yellowjackets, another type of hornet, they build paper nests, which reach peak size toward mid-September. They can attain quite a large size by the fall. The queen in the nest then lays special eggs that develop into the reproductives – the new queens and males – which engage in a nuptual flight. The old queen, and the males once they’ve mated, all die, but the new queens find nooks and crannies in which to hibernate for the winter.

In the spring, the new queens emerge and find a suitable spot for a new nest, and get started on building the paper cells. She lays a few eggs in these cells, and provisions the larvae with insects herself. Eventually they mature into sterile female workers, who then take over the duties of building the nest and caring for the larvae, while the queen goes about laying more eggs.

While the larvae are fed insects, the adults feed on nectar and sap, which is high in sugar, providing energy for powering flight. In addition to this, the larvae are able to secrete a sugary liquid, which the workers also use to supplement their food.

Like most insects, the adults have large, compound eyes, and three ocelli on the top of their head. The compound eyes are primarily used for detecting movement and discerning shapes that are useful in navigating and finding nectar sources. The ocelli are primitive eyes that are only really useful for detecting light and dark (something the compound eyes aren’t good at), which helps the wasps stay upright relative to the ground, and also helps in determining day length, etc. It may be that the insects use one or the other of their two sets of eyes to navigate by the sun, and the artificial lights at night confuse this sense.

You can also see well here the large, powerful jaws that the adult uses for catching and dissecting its prey. They’re not used for eating, since the adults don’t eat solid food themselves, but rather for handing the insects that are taken back for the larvae to feed on.

I love close-ups of insect feet. Wasp and hornet feet (as well as many other insects) are neat because they’ve got little spurs at each of the joint, and two long claws at the tips of the foot. It’s these claws that allow them to climb up vertical surfaces, or even to hang from the ceiling, finding little imperfections in the surface that we can’t detect.

The wasp I caught takes a moment to clean her back legs by rubbing one along the length of the other. Her stinger is usually kept retracted unless she’s planning on using it, so it’s not visible here. Given their size, one would expect the sting of this species to hurt like an expletive, but it’s less painful than bee stings. This is because the stinger of the bee is pulled from the abdomen and continues pumping venom into the victim beyond the initial attack, while wasps, since they need to be able to use their stinger repeatedly when collecting prey insects, only inject a relatively small amount. Blackburnian got stung by one when he was trying to remove it to outside (he made the mistake of swatting it), and it barely swelled up or got sore. Their threatening appearance and old wives’ tales regarding the potency of their sting have resulted in the species being persecuted through much of its native range, however, and there are regions within Europe where the hornet is now endangered.

She’s presumably one of the sterile female workers, as the new queens wouldn’t be flying yet by then. Even with the ordeal of being captured, stuffed in a fridge overnight, and then asked to pose for the camera, she was very well-behaved. The only time she showed any reaction was when I pushed the pencil tip up next to her. Even then, she reared back with her front two legs in the air, paused for a moment to assess the threat, then, deciding it was benign, continued walking along the deck railing. Sure are fearsome looking critters, but really they’re just gentle giants.