November, 2014

Black Webspinner

Many people see this little insect without knowing what it is. In fact, the black webspinner (Oligotoma nigra) is so small and inconspicuous that most people who see it do not even really notice it. Topping out at about 10 mm in length, male webspinners are often attracted to lights, where they fly around with the various moths, flies and other insects. We occasionally see them when they land on the white lampshades in our house. They look disturbingly like winged termites, but are not related at all.

Although webspinners are of no economical or medical significance (they are not agricultural pests and do not bite or sting), they are still very interesting for a drab tiny insect. Females are wingless and live in silken tunnels in ground litter. The winged males must enter the tunnels to mate, and their wings become a hindrance when they need to back up. One solution to this problem is flexibility. The slight breeze blowing the wings of this individual would have no effect on the stiffer wings of a fly, wasp or moth. Wings of males who have "been around" often have creases caused by repeated folding during their subterranean exploits.

While the domestic tunnels are made by females, the males use silk to fashion small retreats in rock crevices and such. I often find them partially obscured in their web coverings on walls near lights.

The silk that webspinners make is unique compared to other arthropods. Spider silk comes from glands in the spinnerets which are at the rear end of the animal. The silk made by silkworms and other caterpillars is produced by glands in the mouth. The silk of webspinners, though, comes from glands in the enlarged segments of their front legs. Just like Spiderman, webspinners produce webbing from their wrists! Obviously, Spiderman had to adopt this more acceptable anatomical anomaly rather than produce silk like a spider would.