Back on October 23, 2023, we had an abnormally warm day of 86℉. I took advantage of this to put out a blacklight, in front of a white sheet, on our back yard fence that night. Because of insect decline, and the role of light pollution in driving down the survival and reproductive rates of insects, I try and blacklight less frequently these days. Never mind that the federal penitentiary, located two blocks behind our house, is lit up like Las Vegas every night. I consider it something of a miracle that we are able to draw any insects to our dim illumination devices, but we get a surprising diversity. This night was no different, despite being so deep into autumn.
One wonderful aspect of putting out a blacklight at this time of year is that we are not inundated with huge numbers of caddisflies, as we often are, especially in late spring. Instead, fall is the season of true bugs (order Hemiptera), lacewings and their allies (Neuroptera), flies (Diptera), select late-season moths (Lepidoptera), and a few beetles (Coleoptera).
Indeed, during daylight hours in late October, the air is positively thick with aphids and tiny leafhoppers, and buzzing with the drone of larger bugs like stink bugs and leaf-footed bugs. Many of these true bugs overwinter as adults, and are seeking places to shelter through the cold months. Some species of aphids move to alternate hosts for the winter, and so have winged individuals for dispersal to those plants. It has been windy, though, and even wingless aphids have been blown everywhere. Our fence is crawling with them, even as I write this on November fourth.
Leafhoppers are among the most speciose of insects in our yard, as both resident insects and "fly-by" individuals for which we have no host plants to support them. Most of that diversity occurs under five millimeters in body length. A two- or three-millimeter leafhopper can still be surprisingly colorful, though.
Planthoppers representing several families were also present at our light, some a little bit worn.
We had three different species of mantidflies, also known as mantispids, at the lights. They are predatory and readily stalk smaller insects drawn to our light source. Their more familiar kin, green lacewings and brown lacewings, were present, too. Green lacewings are frequently brown, or reddish, at this time of year, and also overwinter in the adult stage.
Flies are ever-present, with blow flies spending the winter as adults hidden under the siding of your house, and in other snug cavities. Syrphid flies were still visiting the aster flowers in our neighborhood during the day. What came to the light, however, were long-legged flies, tachinid flies, and pomace flies.
Moths are what entomologists typically deploy blaclights for, and of course there were some of those, too. Some species appear only during the fall, and/or the winter, so it pays to keep the blacklights handy for the odd warm evenings. Owlet moths, geometer moths, and grass veneers are among the usual suspects, but look for much smaller moths, too.
Oh, I almost forgot about barklice (order Psocodea). Three species showed up on October twenty-third, probably representing three different families. Barklice are easily mistaken for planthoppers, or even tiny moths, but they have chewing mouthparts instead of a beak or a proboscis.
Beetles that showed up included several species of ground beetles (Carabidae), small dung beetles (Scarabaeidae), and lady beetles (Coccinellidae), along with representatives of less familiar families.
More warm days are in the forecast for next week, so I may at least flip the front porch light on and check for insect guests. Even the vague warmth of the blacklight results in substantial carnage, with smaller, frail insects perishing from the heat, so that is another reason to use the apparatus sparingly. It is still a great tool, however, for evaluating insect variety and density. More on light pollution to come, in a later post.
Note: Here is the link to all of the arthropods observed on this date on iNaturalist.
