Download Howdy, BugFans, Silverfish, in the Order Thysanura (“tassel tail

Howdy, BugFans,
Silverfish, in the Order Thysanura (“tassel tail”), have been around for a very long time. They’re tied, in
fact, with springtails for “Oldest Insect Fossil” recognition (depending on how liberally you define insects).
About 400 million years.
Most insects have wings, and the ancestors of most of today’s wingless insects once had wings. Insects
like silverfish and springtails are called “primitively wingless” because neither they nor their ancestors
ever had wings. Silverfish do have 6 legs and 3 body parts and segmented bodies, and although their
status has been debated for a long time, they are generally considered to be a primitive insect.
Silverfish are spindle/carrot-shaped, flat (the better to squeeze into those snug spots) and gray with a
metallic “finish” due to a covering of loose scales (the English call them “silver ladies”). A predator that
tries to grab one gets a handful/mouthful of scales and a rear view of a fleeing silverfish. Sue Hubbell, in
Broadsides from the Other Orders, calls them the “greased pig of bug-dom.” She says that they have a
“practical form that enabled them to get on in the world, suited to the changes and challenges the world
has offered” since Devonian days. She labels them conservative and successful, socially gregarious and
“eagerly cannibalistic.”
There are about 250 species of silverfish/bristletails worldwide, 40 in North America, and most are outdoor
critters. Your common, household silverfish, the one that caused the BugLady’s Sainted Granny to store
her daughters’ luggage in the garage when they came home from college, is Lepisma saccharina (“sugartaker”), which lives in cool, damp places. Its antennae and its tails are shorter than its body. It feeds on
house dust, bits of dried vegetation, those small insect body parts that get restaurants in trouble,
sawdust, and starch, which it gleans from wallpaper paste and from the glues used in book-bindings
(which explains the BugLady’s resident population). Hubbell says that back in the good-olde-days, when
men wore heavily-starched, detachable collars, it was common to open the collar drawer and watch
multitudes of silverfish darting for the shadows, and that much of what has been written about them is
more than 60 years old.
The humble silverfish possesses an astonishing sensory system, much of which can be regenerated if
necessary. According to Hubbell, it is essentially deaf and has eyes that indicate only light and dark (it
prefers dark), but approximately six kinds of sense receptors in its antennae tell it about the size and
shape of the spaces it moves through, along with “many other things that are unknown to us in our
largely visual and aural world.” She goes on to say that it possesses “an array of chemical and tactile
sensitivities so varied and precise that we …… can have no real understanding of what a silverfish’s world
is like.” In addition, the “slightest change in air current sets off sensory hairs” in a silverfish’s body. As
its antennae investigate the dark spaces, its tail filaments drag behind, analyzing the substrate.
Wowsers!!
Another surprise is its ardent courtship dance. Advancing and retreating, with antennae and tail filaments
waving and quivering, whirling their abdomens in a torrid choreography, the male and female court. At
the height of their fervor, he spins threads from the tip of his abdomen and encloses his spermatophore
(sperm packet). At his touch, the female advances into his web, picks up the spermatophore, and uses it
to fertilize her eggs. She must dance each time she lays eggs.
She lays her eggs in cracks and crevices. If she picks a hospitable microclimate, her eggs will hatch
looking like mini adults and will grow slowly. If not, her young will not develop properly within their eggs
and will die while hatching. Silverfish live several years and molt more than a dozen times (they are
unusual among insects because they continue to shed their exoskeletons routinely after becoming
adults). A molting silverfish is, momentarily, a helpless silverfish, and it may get cannibalized if one of its
confreres discovers it thus incapacitated.
Who knew???
The BugLady