November Caddisflies

2013 November 2

By the time November rolls around, we’ve usually had several hard freezes and at least one significant snowfall, and so most of the insects are gone by then. But these show up pretty reliably at our porch light every November, and in 2012 I photographed them on both November 11 and November 22:

These are Northern Caddisflies, in the family Limnephilidae. And based on their shape, coloration, and the time of year they were emerging, I’d say they are probably in the genus Frenesia.

Caddisflies kind of resemble moths, but are actually in a separate order. They tend to have that triangular wing shape from the side, and long antennae.

The other obvious way that the adults differ from moths, is that instead of having colored, powdery scales on the wings, they have little hairs (which can be pretty easily seen around the edges of the wings).

By flying this time of year, they avoid a lot of predators. For example, this next one got caught in a spider web near the light, but eventually got away again because the spider was no longer around.

Our porch light is a hot dating spot. There are generally a number of mating pairs on the wall around the light. They seem to be more willing to mate around the light than most other insects. Moths at the light generally seem to be to dazed to do anything but flutter around, but the caddisflies seem to treat it more as a good place to meet up.

Here’s a few more mating caddisflies, from back in November of 2010. Which shows this sort of thing has been going on around our house for some time.

Not all caddisflies fly in November. In fact, most species seem to fly in the spring and summer. But, the ones in our yard seem to be almost exclusively this particular November-flying species.

The larvae of caddisflies are aquatic, and they mostly live on the bottom of streams inside of cases that they build out of sticks, sand, and other debris held together by silk. I think that ours are coming almost entirely from the tiny creek that trickles out of a spring about 100 feet to the north of our house. Since they are aquatic, and most streams or other bodies of water don’t actually freeze all the way to the bottom, they can actually continue to be active and feeding all winter long.

To wrap things up, here is a photo of a completely different caddisfly species that we had to go all the way to Otter Lake to catch. This was one of the Spring-emerging species (we caught it in May 2010), and it is clearly different from the ones in our yard in the fall. It still has the characteristic body shape of a caddisfly, though.

The people who take the keenest interest in caddisflies tend to be people who fly-fish for trout. Caddisflies are one of the aquatic insect species that emerge as flying adults all at once in large masses, and when this happens it whips the fish into a bit of a feeding frenzy. And if anglers can get into the fray with halfway convincing replicas of caddisflies on their hooks, the odds of catching fish go way up.

One Response leave one →
  1. Carole permalink
    November 2, 2013

    Have only seen photos of the larvae. I’ll have to keep my eye out for the adults. We have so many frogs and geckos on our porch insects don’t stand a chance.
    I’ve heard caddisfly larvae are an indicator of good water quality.

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