Mystery Midge with “Kite Tail” Eggs

Mystery Midge with “Kite Tail” Eggs

Lake Umbagog along the Maine/New Hampshire border, is home to a chironomid midge with an unusual egg-laying behavior. Beginning about 7 a.m. on calm mornings in mid- to late June, female midges come drifting in over the lake with long strings of eggs hanging from the tips of their abdomens. Chironomids resemble small mosquitoes but they don’t bite. This is an adult female of the genus Stenochironomus. Males are often called “fuzzbills” because of their plumose antennae, which they use to detect the sound from a female’s buzzing wings during the mating swarms. The family is hugely diverse in freshwater habitats where their larvae comprise a large portion of the invertebrate fauna. Following pupation, adult flies emerge from the water to mate and lay eggs. The behavior of this Umbagog species is unlike any other we are familiar with, in that females extrude their eggs in flight into a long string which they eventually release into the water. As midges go, this species is rather large but still only a few millimeters long. However, when backlit by the rising sun and viewed against the dark coniferous forests in this way, with a 10 to 20 centimeter long string of eggs hanging from the tip of their abdomens like a tail on a kite, they’re quite conspicuous and can be seen from about a hundred meters or more. These females seemed to drop down from near the tree canopy as they extrude their eggs, so presumably the males were swarming up in there somewhere, and the females entered those swarms to mate prior to this egg extrusion. Sherman Roberts was able to capture this video. It’s a little shaky because we didn’t have a tripod handy, and you can see the autofocus has a little trouble pulling out the midge, but it definitely captures the effect. [no narration] As Sherman shot the video from the bank, I was paddling around trying to shoot some stills. I got a number of fairly decent ones. [no narration] This last one I framed against the blue sky … it looks like a jet with a contrail. We know this midge is an orthoclad, but we don’t yet know the species, or even the genus, as the only specimens we have in hand are adult females, which cannot be reliably identified. So in an attempt to figure out what they are, I intercepted a couple of females that were about to release and put their eggs into a jar of water, with the hope that we can rear them and figure out what species they are. This is one of the strings I intercepted, in the jar of water. The gelatinous tube retains its integrity in the water and the individual eggs can be seen within. This is related species, which also lays its eggs in tubes, but this one lays directly into the water. You can see the developing embryos here, which are only about 200 microns long. When they’re ready to drop their eggs, the Umbagog orthoclads descend to the surface and the eggs are released. Most females then fly off. This one had a little trouble getting back into the air. Notice the water surface is covered with water striders, who may be waiting for just such an opportunity to snag a prey item. This individual clearly made it back into the air. Later in the morning we saw individuals with shorter strings. These may have been ones that had already dropped most their eggs on an earlier flight.

Eugene Islam

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