(Greek, thysanos = fringe)
This small, cosmopolitan order includes some 370 species in four living families. It is more diverse than the Archaeognatha, structurally and ecologically. Many species are inquiline, and those living with humans are familiar insects of some economic importance.
Silverfish are primitive, wingless insects covered with silvery scales that rub from the insect's body very easily. The scales are the reason for the common name "silver"-"fish". Silverfish are small and flattened. Compound eyes are either reduced or absent. If eyes are present they are formed of single elements. One, two or three simple eyes (ocelli) may be present. Mandibles are present but may be covered by a 'beard' of hairs. Three abdominal filaments are present. Two, equal length appendages (cerci) arise from the sides of the second last abdominal segment. A third (median caudal appendage) arises from the middle of the last abdominal segment.
Silverfish may live for up to four years. Various species of silverfish are adapted to human dwellings, but others use caves or live under bark. Several species are commensals in ant or termite colonies. Firebrats are a group which have adapted to the high temperatures around ovens and fireplaces.
Silverfish resemble the species of another ancient and flightless insect Order, the Archaeognatha (bristletails). Bristletails differ in that they have well developed compound eyes and the middle tail bristle is much longer than the pair of side bristles. Silverfish are noctural insects i.e. they feed and are active at night.
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.
Bushland species, feed on lichens and fungi. In commensal situations, silverfish have been observed to "steal" nectar droplets from ants that are transferring regurgitated nectar from one to the other. Firebrats appear to feed on flour and similar materials. Household silverfish have been noted as attacking almost anything that contains food value: paper surfaces, starchy foodstuffs, silk, their own cast skins, other dead insects, cellulose materials (cotton, plant debris), etc.
Silverfish do not appear to have any importance in either agriculture or horticulture. Their significance seems to be limited to the nuisance effects or damage done to household or paper materials stored undisturbed for extended periods of time (e.g. archival books in libraries and museums). In bushland, silverfish undoubtedly play a role in litter re-cycling and food chains.
As with the Archaeognatha, the Australian fauna is poorly known. Major factors contributing to this include the fragility of silverfish and their extreme speed when disturbed, which make the collection and preservation of intact specimens very difficult.
Denis (1949), Paclt (1956), Delany (1957) and Sharov (1966) discussed the Apterygota, including Thysanura, and Womersley (1939) reviewed the Australian fauna.
Cursorial, more or less flattened, primitively wingless insects. Body scaled or bare, with or without pigment. Compound eyes reduced or absent, never contiguous; ocelli absent except in Lepidothrichidae; antennae elongate, flagellum filiform; mouth-parts ectognathous; mandible dicondylar; maxillary palp 5-segmented; thorax not strongly arched, pleura exposed; styles present at most on abdominal segments 2-9, commonly less; 2-7 occasionally with exsertile vesicles; female with well-developed, slender ovipositor; cerci and appendix dorsalis filamentous, generally elongate and subequal in length, sometimes short, cerci strongly diverging from body axis.
The four introduced genera, and the pest species belonging to them, are cosmopolitan or nearly so.
have wide distributions including Africa, Asia, South America and some Indian Ocean and Pacific islands (Paclt 1967).
is endemic, whereas
are known from Africa, Australia and South America, and
is Asian and Australian (Paclt 1963).
is restricted to Australia and Pacific islands (Smith 1988).