Silverfish and firebrats belong to what is thought to be one of the most primitive of living insect orders. This order is characterized by the three long tail like appendages arising from the tip of the abdomen, which is responsible for this group’s common name-bristletails. They have chewing mouth parts, long antennae, and the body is nearly always covered with scales. Viewed from the top, these insects have a carrot-shaped outline. In size, silverfish range from about 1/2 inch in the common silverfish to about 3/4 inch in the gray silverfish. Two rather long, segmented antennae protrude from the head of all described species of silverfish and from the firebrat. The firebrat’s antennae extend beyond the tip of the abdomen, often being curved back toward the rear of the insect. Both silverfish and firebrats are capable of swift movement, and the silverfish are known for the ability to move sideways or even jump when disturbed. Since the bodies of these insects are flattened they can find harborage in very small cracks or crevices’, even within the confines of narrow book bindings, the loose pages of books, or in the corrugations of cardboard. Silver fish and firebrats mature through the developmental process known as ametabolous metamorphosis. The newly hatched silverfish nymphs look like tiny adults except that the characteristic body scales do not usually appear until at least the third molt. The number of times that silverfish or firebrats molt has not been agreed upon. They may be like other primitive arthropods that continue to molt throughout their life period of two to three years.
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Feeding Habits and Damage
Some aspects of their behavior, particularly feeding behavior, should be understood so as to optimize the development of a strategy to control these insects when they become structural pests. The feeding habits of the major species of silverfish are very similar. These insects may roam for some distance in search of food, but once they have found a satisfactory source, they remain close to it.
Silver fish consume both carbohydrates and proteins. Silverfish can be cannibalistic, eating cast skins and dead and injured silverfish. Silverfish damage to paper products can be significant. Cotton and silk are attacked when the texture is suitable for feeding. Silverfish will also feed on materials of both animal and vegetable origin, including wheat flour, whether or not it contained sugar or salt. Silverfish are extremely fond of flour and starch; this fondness, in part, accounts for their not infrequent appearance in breakfast cereals.
Silverfish are pests of paper, particularly paper with glaze on it. They are especially fond of the sizing in paper, which may consist of starch, dextrin, casein, gum and glue. These insects often attack wallpaper, in which they may eat holes or remove the paste, which eventually causes the paper to become detached from the wall. As a rule, books and papers that are in constant use are damaged little, but even these items may show ragged edges and markings on the bindings.
Damage by silverfish to textiles may be recognized by the presence of feces, scales, irregular feeding marks on the individual fibers of the textile, and, in certain instances, especially in the case of linens, by yellowish stains. Where damage to textiles is believed to be due to silverfish, a card coated with flour paste may be placed in the vicinity. Subsequent examination for feeding marks upon the card will reveal whether silverfish are present.
Silverfish are extremely resistant to starvation and may be kept alive in a glass jar without food and water for weeks. Some species of silverfish can be very resistant to high temperatures and low relative humidity’s. Silverfish have been found living in attics where temperatures have been known to reach 130 degrees F with relative humidity’s of less than 15% moisture.