Moulting walkingstick

walkingstick with shed exoskeleton

Regular readers will have likely noted that my posts have been a little bit sparse recently. This is not for any lack of possible content or interest in my part – I have quite an assortment of photos sitting on my hard drive that I’ve taken over the last few weeks and would have made for good posts. Mostly it’s just been that time has been short. I expect it to become shorter still, as we come up on the manuscript deadline for the field guide to moths and my co-author Dave and I work diligently to make sure we’ve got all the pieces pulled together. I’ve been thinking for a while that I may need to put the blog on a semi-hiatus for the final month. I won’t shut down altogether, but I will probably only be posting once a week. Once the material has been submitted, at the beginning of September, I should be able to resume my normal posting schedule. So I hope you’ll all bear with me till then. (Incidentally, although we submit the material in about a month, the book itself will be another year and a half before it hits shelves – this is because of the time required for editing and layout and proofing and everything else that goes into producing a book, which, it turns out, is all rather more time-consuming than I’d realized.)

Today’s photos were taken at our Blue Lakes MAPS station this past week. It’s a Northern Walkingstick, Diapheromera femorata, which just recently emerged from and is still clinging to its freshly-moulted exoskeleton. Dan actually found it hanging from a shrub beside the path; he finds a lot of my most interesting critters. Walkingsticks don’t have distinct larval and adult stages; instead, they hatch from the egg resembling a miniature adult, and just grow larger with each successive moult. This individual is a male, I think, as determined by its “twigginess” (females are stockier in build). I posted about walkingsticks a couple of autumns ago when I had one arrive at my moth trap one night. You can read the original post here.

walkingstick with shed exoskeleton

All legs

Northern Walkingstick, Diapheromera femorata

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.

Northern Walkingstick, Diapheromera femorata

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.

Northern Walkingstick, Diapheromera femorata

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.

Northern Walkingstick, Diapheromera femorata

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.

Northern Walkingstick, Diapheromera femorata

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.

Northern Walkingstick, Diapheromera femorata

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).

Northern Walkingstick, Diapheromera femorata

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?