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Excerpts from Jim Conrad's
Naturalist Newsletter
from the March 3, 2013 Newsletter issued from the valley of the Dry Frio River in northern Uvalde County, southwestern Texas, on the southern border of the Edwards Plateau; elevation ~1750m (~5750 ft); N29.62°, W99.86°; USA
TEXAS PINE SILVERFISH
On a nearby rocky hillside my picking up a rock caused a half-inch long (11mm), slender, six-legged, stiff-bodied critter to skitter across the ground. That's him above. The head showing the body heavily mantled with scales is shown below.
The arthropod was conspicuously segmented and grayish like a centipede but with six legs he had to be an insect, and centipedes with their many legs aren't insects. He was shaped like a silverfish but I think of silverfish as whitish and more soft-bodied than this one looked. Still, volunteer identifier Bea in Ontario was convinced it was a member of the Silverfish Family, the Lepismatidae, a family holding about 190 species of primitive, wingless insects. Therefore I was tickled to find on the Internet a freely available 1972 paper entitled A Review of the Silverfish of the United States and the Caribbean Area.
That paper led me to the name: ALLACROTELSA SPINULATA, sometimes known as the Texas Pine Silverfish, despite the fact that it occurs far beyond Texas -- throughout most of the western US and into Mexico. However, judging from the lack of pictures and information about the species on the Internet, it must be rarely noticed, maybe because normally it occurs beneath objects on the ground and under tree bark. You just have to blunder upon one, as I did.
So, this was a good find, a reminder that all silverfish aren't like the pale, flexible-bodied critters we see in basements and libraries with old books. The silverfish we normally see in our homes -- the Common Silverfish, Lepisma saccharina, and the Firebrat, Thermobia domestica -- are invasive species, but the Texas Pine Silverfish is a native species who politely stays in the woods not bothering humans at all. They are omnivorous scavengers, well-mannered little garbage collectors who unobtrusively work out of sight and out of mind.
And when we see them, taking into account their primitive roots, we can think of their winglessness as a feature of a time so long ago that insects hadn't yet settled on the notion that wings might be a good idea.