House Centipedes

One of the most confounding, and arguably creepiest, creatures I am asked about at AllExperts.com has to be the “house centipede,” Scutigera coleoptrata. Neither insect nor arachnid, it is variously described to me as spidery, an animated feather, a speeding, ghostly apparition, and plenty of other epithets born out of both fear and fascination.

This species seems to be genuinely domestic, occurring mostly in and around human habitations where these venomous predators prowl in search of other invertebrates to eat. It is thought to have originated in the Mediterranean region, but unless one starts speaking Italian or Greek, you could fool me. International commerce has now succeeded in transporting the house centipede to virtually all inhabited corners of the globe anyway.

Related species in the genus often live in caves, and indeed the long legs and antennae of this animal are characteristic of habitats where visual acuity is much less important than a sense of touch. The lanky build of these creatures also makes them appear much larger than the 25-35 mm body length of the average specimen. Couple that with the incredible speed at which they can travel, and you have the heebie-jeebies come to life. I confess they can even freak me out at times because they can climb walls and scurry across ceilings at about Mach 7.

Fortunately, house centipedes are totally harmless to people and pets (well, if you have a flea circus I guess you’d better be careful). I encourage folks who encounter house centipedes to just let them continue their pest control patrol, like this one is doing, or usher the centipede into a container and release it outdoors in a woodpile, rock wall, or other sheltered situation where it will be equally happy hunting for food and mates. Those approaches are certainly preferable to "Honey, can you get me a shoe? A really big shoe?"

Webspinners

One of the most fascinating and unique insects to be found here in Tucson is the “webspinner.” They even have their own order, the Embiidina (formerly Embioptera). Adult males like the one pictured above are drawn to lights at night, and at under 10 mm, they are easily mistaken for alate (winged) termites.

I first became aware of webspinners because one of my childhood idols, insect photographer extraordinaire Edward S. Ross was also the world authority on these obscure insects. He still is the expert on embiids, in fact. Discovering new species of webspinners took Dr. Ross all over the globe, as the diversity in this order is mostly tropical. During his expeditions, Ross also took amazing images of other insect species, many of which graced the pages of National Geographic magazine.

Nearly everything about webspinners is bizarre. They go through a simple metamorphosis, with immature individuals resembling adults, but the females never develop wings. Most species are live in galleries of silken tubes under loose bark and stones, or leaf litter, often in a matriarchal congregation of a parent female and her offspring. The insects can move quickly through their silken tunnels, usually moving backwards. The wings of adult males flip forward so they don’t catch on the silken walls during backwards maneuvers.

Perhaps the oddest feature of their anatomy are the front legs. The swollen “feet” (tarsal segments) contain the glands from which the silk is spun. This appearance of having ankle weights or Popeye forearms easily separates webspinners from winged termites, small stoneflies, and other look-alikes. Even the youngest web-spinner can do just that: spin silk.

Webspinners feed mostly, if not exclusively, on decaying vegetable matter, though adult males do not feed at all. The mandibles (jaws) of males are modified for chewing holes in the galleries of females, and for grasping the woman of his dreams during courtship.

Three families of webspinners are known to occur in the southern United States, with one species reaching as far north as southern Oregon. Our common Tucson species is Oligotoma nigra, but it is not native, having come traveled in date palm cuttings from Egypt and the Persian Gulf sometime in the 1800s. It is believed that India is the true place of origin for this insect. Now it is widespread in the tropics, and ranges from San Antonio to southern California, and north to Utah in the U.S. There is also a documented record from Arkansas.

For more information on these amazing invertebrates, I recommend the World Wide Webspinners website, recently constructed.