Saturday, November 4, 2023

Last Night to Blacklight?

A green mantisfly (left) and a leafhopper parade across the top of the sheet behind our blacklight at night.

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.

Japanese Maple Leafhopper

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).

Trumpet Vine Moth

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.

Mirid plant bug, Hyaliodes sp.

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.

Leafhopper, Erythridula sp.

Leafhopper, Norvellina helenae

Leafhopper, Gyponana sp.

Leafhopper, Gyponana gladia?

Red-banded Leafhopper, Graphocephala coccinea

Planthoppers representing several families were also present at our light, some a little bit worn.

Delphacid planthopper, Liburniella ornata

Northern Flatid Planthopper, Flatormenis proxima

Derbit planthopper, Otiocerus stolli

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.

Mantidfly, Dicromantispa interrupta

Green Mantidfly, Zeugomantispa minuta

Mantidfly, Dicromantispa sayi

Green lacewing, Chrysoperla sp.

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.

Marsh fly, Dictya sp.

Unidentified tachinid fly

Unidentified long-legged fly

Black scavenger fly, Sepsis sp.

Mating pair of leafminer flies, family Agromyzidae

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.

Green Cutworm Moth, Anicla infecta

Ailanthus Webworm Moth, Atteva aurea

Corn Earworm Moth, Helicoverpa zea

Ipsilon Dart, Agrotis ipsilon

Juniper-twig Geometer, Patalene olyzonaria, I believe.

Grateful Midget, Elaphria grata

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.

Common barklouse, Indiopsocus sp.

Narrow barklouse, Graphopsocus cruciatus

Common barklouse, Trichadenotecnum alexanderae species complex

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.

Vivid metallic grouond beetle, Chlaenius tricolor

Colorful foliage ground beetle, Lebia vittata

20-spotted Lady Beetle, Psyllobora vigintimaculata

Antlike flower beetle, Notoxus sp.

Silken fungus beetle, family Cryptophagidae.

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.

Aphid, Drepanaphis sp.

Note: Here is the link to all of the arthropods observed on this date on iNaturalist.