Overview
(Greek, archaeos = ancient; gnatha = jaw)
Bristletails are primitive wingless insects. At first glance they resemble silverfish, however silverfish have three abdominal filaments nearly equal in length. In bristletails, the central filament is much longer than the side two. Unlike silverfish, bristletails have well developed compound eyes. The compound eyes are large and meet on the back of the head. Three simple eyes (ocelli) also occur on bristletails. Bristletails have well developed mandibles which are partially hidden in the head. The antennae are long and resemble a chain of beads (moniliform). Bristletails are usually nocturnal and have an interesting habit of "arching and flexing" the body to give a springing action similar to springtails. Bristletails are found in litter, moss, lichens and other similar habitats.
This small, homogeneous and cosmopolitan order includes about 350 known species in one extinct and two living families. Previously grouped with the Thysanura, these silverfish-like insects are characterised by their unique and ancient monocondylar mandibles (Manton 1964). Denis (1949), Paclt (1956), Delany (1957), Sharov (1966) and Hennig (1969) reviewed them (as part of the subclass). Womersley (1939) documented the then-known Australian fauna and Sturm (1980) reviewed
Nesomachilis
.
There is no metamorphic life cycle: egg-larva-pupa-adult. The juvenile (nymph) emerges from the egg as a replica of the adult and develops through moults. Eventually a final moult leaves it sexually mature.
Bristletails feed on plant detritus, algae, lichens and mosses and have no known importance apart from the usual roles played by litter re-cycling organisms in ecosystems.
Description
Fusiform, subcylindrical, primitively wingless insects, with the ability to jump. Body with or without hypodermal pigment, bearing pigmented scales. Compound eyes large, contiguous; ocelli present; antennae elongate, flagellum filiform; mouth-parts ectognathous; mandible with a single articulation; maxillary palp long, 7-segmented; thorax strongly arched, the terga extending over pleura; styles often present on coxae; abdominal segments 2-9 with ventral styles, 1-7 generally with 1 or 2 pairs of exsertile vesicles; female with well-developed, slender ovipositor, without gonangulum; appendix dorsalis elongate, filiform, longer than filiform cerci.
Distribution
The Australian fauna is not well known. All the species belong to the Meinertellidae, the more primitive living family, which is essentially southern (Sturm 1984); the Machilidae are found principally in the Northern Hemisphere (Denis 1949).
Allomachilis
is endemic, and
Nesomachilis
is restricted to Australia, New Zealand and Melanesia including the island of New Guinea.
Machiloides
, to which
Nesomachilis
is closely allied, is principally South African, Madagascan and South American (Wygodzinsky 1948, 1955).