FEBRUARY
1990

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

02-09-90

WINTER STONEFLIES

Insects, like snakes, frogs and salamanders are cold-blooded organisms.  These animals cannot regulate their body temperature and are generally inactive during the winter.

Some insects, such as the familiar cockroach, cope with cold temperatures by living in our dwellings.  But a few hardy insect species are seen during the winter months in the great out-of-doors.

One such insect, the winter stonefly, is appropriately named – at least the season in its name is accurate.  Winter stoneflies can be found crawling around during sunny days from January through April.

But stoneflies really aren't flies at all.  Some do fly, although their aerial forays are less than spectacular.  A few species of stoneflies have given up flying altogether, and for good reason:  they lack wings.  These wingless individuals depend on their six little feet to get them where they want to go.

Technically, stoneflies are members of the insect order Plecoptera.  Insects in this order are rather soft-bodied and have antennae-like appendages, called cerci, protruding from their abdomen.

These rather drab-colored insects are found near streams or rocky, lake shores.  The immature stoneflies, called nymphs, live in the water and are often found under stones.  That's the basis for their common name, stonefly.

The stoneflies that show up during the winter months are normally active in air pockets that form between the ice and the surface of the water of streams.  At a time of year when most insects are out of sight, stoneflies take advantage of the higher temperatures in such miniature greenhouses to be active.  During warm seasons when the ice disappears from streams in midwinter, as it has this year, stoneflies show up in abundance on fence posts, bridges and other structures in the vicinity of the streams where they emerged.

Why are these insects active during the winter?  No one knows for sure.  One suggestion is that it avoids competition with other insects.  The stonefly has discovered a time of year when it doesn't have to compete with the teeming hordes of insects that show up during the warmer months.  As far as insects go, it has the whole world to itself.

So what does the winter stonefly to under such circumstances?  Like any good adult insect, it does what nature has designed it to do:  it mates and lays eggs.

And what does it eat?  Nothing at all.  You see, the winter stonefly doesn't feed in the adult stage, which is fortunate, since there is probably very little to eat under the ice on a winter's day!

 

Writer: Tom Turpin
Editor: Olivia Maddox