Tuesday, January 28, 2014

Winter Insects and a Spring Foreshadowing

With the extreme cold snap and the slow march of winter, most people think that insects and other small animals would be too chilly to make an appearance. Their diminutive size might lead one to think that they would freeze solid out in the environment. For the most part that is true: insects tend to either hibernate or migrate during this time of year to avoid extreme cold. But what about those that enjoy the cold? Many groups only come out this time of year and have special adaptations (such as natural antifreeze - apparently common in Arctic species) to survive the low temperatures. Here are a few cold-loving groups that come to mind:
  • winter crane flies (Trichoceridae) - a family of mosquito-like flies related to their warm weather cousins, the true crane flies (Tipulidae); you may have seen them at your porch light
  • winter stoneflies (Taeniopterygidae) - develop in well-oxygenated streams especially in the mountains; they emerge in the fall, winter and early spring
  • snow crane flies (Tipulidae: Chionea sp.) - these small, wingless, spider-like flies only come out in cold weather, usually being observed on snow
  • snow scorpionflies (Boreidae) - these tiny, hopping insects are only found in the Northern Hemisphere, most commonly in mountainous areas with snow; their larvae feed on mosses
  • snow fleas (Hypogastrura) - often seen in masses on snow, these tiny springtails (not true fleas) enjoy the cold weather
  • some dung beetles (Scarabaeidae) - in my studies on the seasonality of dung beetles in NC, I found that a few species were only present in the cooler months of the year (below)
Aphodius distinctus is one of the dung beetles that is present in the fall and winter, but not during other times of the year (from Bertone 2004).

More types of insects than you think are active in the frigid times of the year*. Most go unnoticed (maybe because we are inside more) and pass their days doing what they do and not bothering us.

Others are a sign of what's to come. Despite their autumnal name, the fall cankerworm moths (Alsophila pometaria) have been out and about for a few months. In fact, just two weeks ago I was alerted to a plethora of females mistaking some campus building pillars for trees. The wingless females were clinging to the cement and some had started to lay their eggs. No doubt others had already done so since they appeared in the late fall.

Female fall cankerworms are strange moths that lack wings (though not unique among Lepidoptera).

The tiny, barrel-shaped eggs of the fall cankerworm laid in a nice batch.

I was also surprised by the abundance of male fall cankerworms at lights and elsewhere this year - something I have not particularly noticed in the past. Males, unlike the wingless females, have large, drab wings and look...rather moth-like and fairly mundane.

Male fall cankerworms are fully-winged and can be found at lights during the cooler months.
So what does this mean? I am assuming the abundance of adults is a direct result of the previous spring's many, many larvae that plagued local trees and bushes, raining down from above on silken strands. But does that mean that we will have as many (or, even more) this coming spring? I am not sure, but we will know in a few months when these little guys come out:

Fall cankerworm caterpillars are all too familiar "inchworms" in recent years.
Oh, and don't forget about spring cankerworms! The silver lining? At least it will be warm outside.

*there is even a whole group of insects, the ice crawlers (Grylloblattodea) that only exist in the cold mountains of the Northern Hemisphere, though in the US only in the Western part of the country; they cannot live much above freezing and will die sitting in a person's hand!

1 comment:

  1. I didn't realize the male cankerworm had wings. That is so cool.