INSECTS

Silverfish

Silverfish

Order – Thysanura
Family – Lepismatidae
Species – Lepisma saccharina

Appearance
About 10 –15 mm although some species can grow to 20 mm. The three thoracic segments each bear a pair of small legs. The antennae are long and many segmented. The abdomen consists of eleven segments and terminates with three long segmented bristle-like processes, one central and two lateral and additionally there is a small number of rod-like appendages arising from the hinder end. Often described as 'carrot-shaped'. gray or silver-colored; three filaments extend from rear.

Habitat
They will tend to travel some distance in search for food, but once a satisfactory food source is found, they remain close to it. They hide in cracks during the daytime and become active after dark. In doors they will be found in kitchens and bathrooms. Those found in sinks and baths do not come up the drainpipe but have become trapped after sliding down the smooth wals while searching for food. Outdoors they are found under mulch. They prefer room temperature areas and high relative humidity 75% to breed and multiply. They move swiftly and can jump.

Diet
The mouthparts are adapted for biting and scraping away surfaces. Prefer starches, sugars, and proteins. They will feed on any starch-based products in or on book bindings, glazed paper, postage stamps or similar sources, including dead insects.

Damage
Damage is usually in the form of grazing. They will eat the starch filler between the warp and weft of cloth-case bindings. Likewise any deposits of starch on wallpaper and other paper products. The damaged edges of paper will be very irregular or notched, and the sizing, or coating, of the paper will be removed in an irregular pattern. With heavy infestations, irregular holes will be eaten through the paper. Book bindings will have tiny irregular scrapings. Silverfish feces, when present, are small, dark, and loose. Yellow stains, scales, and/or feces may also be evident on the textile being attacked.

Reproduction
Eggs are elliptical and about 1 mm long. When first laid, they are soft and white; they turn yellow and eventually brown after several hours. Eggs are laid singly or in batches of two to three, and are deposited in crevices or under objects. Under optimum conditions, an adult female lays an average of 100 eggs during her life span. Eggs hatch at temperatures ranging from 22 °C to 32 °C. Optimum temperature is about 22 °C. At this temperature the average incubation period is 43 days.

The first-instar nymph moults in 7 to 10 days, and each subsequent instar (stage between moults) takes about 2 to 3 weeks for development. Nymphs undergo six to seven moults.

A life cycle of 7 to 9 months has been observed that resulted in three to four generations every 2 years. These pests are long-lived and are capable of reproduction after 3½ years at 22 °C. Adult females have been observed to alternately lay eggs and moult, and may moult as many as 50 times. Live to five years.