File: <heading

The Apteragota presently contains only one order, Thysanura -- <Adults> & <Juveniles> --, while the Protura, Diplura and Collembola have been moved to a separate class Entognatha. The Thysanura are known as silverfish, bristletails and firebrats. There are over 310 species of these tiny insects known worldwide. The name "silverfish" comes from the fact that they are covered with scales that cast a silvery hue and from their undulating movements. The name "firebrat" refers to different species that congregate around ovens and are often called "little oven birds. These prefer high temperatures of 98-deg. Fahrenheit.

Their mating habits are peculiar. The males drop a spermatophore during a "mating dance." The female then picks up the spermatophore from the substrate.

The Thysanura have biting mouthparts, antennae that are many-jointed; compound eyes (although most are completely blind); an abdomen with eleven segments, some or all of which bear styliform appendages that may represent the coxites of limbs no longer present. Jointed anal cerci are also present. They all have a well-developed tracheal system and eleven abdominal segments. The 11th abdominal segment bears cerci and a terminal filament. They have external genitalia as the ovipositor emanates from the 8th abdominal segment.

Lepisma saccharina, the common silverfish, which inhabits dwellings of humans, and (Machilis) Petrobius maritimus, found above high-tide mark along the seashore and estuaries, are common examples. In Petrobius interesting features are presented by the well-developed superlinguae and the jointed mandibles, both of which are primitive characters. The superlinguae in Petrobius are paired structures attached to the hypopharynx and have inner and outer lobes and a palp-like process. Notwithstanding a superficial resemblance to maxillae they have no segmental value. They are homologous with the crustacean paragnaths.

Molting. -- These insects may molt more than 41 times. After the 8th molt the sexes are distinguishable. Molting continues after the eggs are laid, which occurs after the 36th molt.

Longevity. -- Their longevity is about three years.

Legs. -- Their legs are modified to withstand surfaces with high temperatures. Their tarsi are "heat resistant." However, they are handicapped by not being able to cling to smooth surfaces. They also are fast runners and the only Insect order with a remnant of abdominal legs.

Economic Importance. -- Thysanura are able to digest rayon and other wood products, just as are the Isoptera (termites). Mostly they consume dead organic matter, such as materials that contain starch, e.g., books, bindings, and wallpaper paste.).

-------------------------------------------

Details of Insect Taxonomic Groups

Examples of beneficial species occur in almost every insect order, and considerable information on morphology and habits has been assembled. Therefore, the principal groups of insect parasitoids and predators provide details that refer to the entire class Insecta. These details are available at <taxnames.htm>.

==============

References

Introduction Contents►