I’m not sure what’s going on this summer, but the bug populations seem like they’ve been off their usual patterns. The black flies boomed and suddenly busted in May, and the dreaded deerflies seemed to disappear as soon as I mentioned them. No regrets, no tears goodbye there.

The butterflies are a different story. Usually the first mourning cloak — beautiful rich brown wings, gold-fringed with blue spots in a black lining — shows up in the driveway as early as April, and individuals flit up and down for much of the summer. This year, I have not seen one of them. White admirals, which are counterintuitively black-winged with white spots lining a fringe of sweet blue markings, straggled in later than usual this year and nowhere near as numerously as in past summers. There have been a few cloudless sulphurs, summer azures and cabbage whites, and visitations by a couple of viceroys, but no monarchs — my casual efforts to get milkweed, their vegetation of choice, growing along the driveway have been unsuccessful. A lot of what I believe to be pearl crescents, small orange and black blurs in perpetual motion, have danced through all summer. Also a lot of moths, as usual, worshiping the porch light at night.

My summer-wings identification skills are negligible, really, but there are three categories of lepidopterans: butterflies, skippers and moths. The distinction is in their antennas. Butterflies’ are slightly knobbed at the end, skippers’ are “hooked,” and moths’ are “feathery or threadlike,” according to one field guide. Butterflies tend to be more brightly colored than moths. Skippers are sort of chunky and moth-shaped but butterflylike. In general, butterflies are active during the day and moths at night, though there are exceptions. Most butterflies hold their wings upright when perched, while moths fold the wings down over their backs.

Early this summer a pretty large population of what were pretty surely Canadian tiger swallowtails (Papilio canadensis) filled the backyard every sunny day, more than we normally see in June and July. Fairly large, bright yellow butterflies with black lines and fringes, and ornate points on the tail of their hindwings, which is the earmark of the many swallowtail species.

I say these were “pretty surely” Canadian tiger swallowtails because almost identical to them are the Eastern tiger swallowtails (Papilio glaucus). The Eastern tends to be a bit larger (with wingspan around 2½ to 4½ inches, while the Canadian is around 2 5/8 to 3 1/8 inches, according to the guides), and the Eastern has a narrower black band on its hind wing. They’re so similar it’s tough to make the distinction when they’re in flight, but the northernmost range of the Eastern tiger swallowtails is southern New Hampshire and Vermont. The Canadian’s range runs from north of the Canadian treeline south (a rare black female morph has been identified in Newfoundland) into New England. So in Troy, they must be Canadian.

They’re widespread, so if you pay attention, you’ve almost certainly seen them. Their preferred habitat is evergreen and deciduous woods edges (that’s our backyard). They feed on nectar from plants, and they’re also puddlers, meaning they’ll gather around mud puddles and wet sandy shores. They’re drinking, but the lepidopterists are not sure they fully understand the activity. For one thing, the puddlers are mostly young males, suggesting some link to reproductive processes. And studies have shown the butterflies are absorbing salts that at least in some species are important to egg production, so it’s thought the males transfer salts, and maybe amino acids, to the females during mating.

The Canadian tiger swallowtail has one flight (or brood) covering May to July, while the Eastern tiger swallowtail has two or three flights, which in the northern part of the range go on all summer. And sure enough, we’ve seen very few in the last week or two, compared to the gorgeous dance in May and June.

Dana Wilde lives in Troy. You can contact him at [email protected] His recent book is “Summer to Fall: Notes and Numina from the Maine Woods” available from North Country Press. Backyard Naturalist appears the second and fourth Thursdays each month.