62 



The Simplest Insects 



causing it to loosen, and infests dry starchy foods. It runs swiftly and 

 avoids the light. It can be fought by sprinkling fresh 

 pyrethrum powder in bookcases, wardrobes, and 

 pantries. Another species, L. domestica (Fig. 93), 

 called the bake-house silverfish, is often common 

 about fireplaces and ovens, running over the hot 

 metal and bricks with surprising immunity from the 

 effects of the heat. This habit has gained for it in 

 England, according to Maria tt, the name of "fire- 

 brat." It can be distinguished from the species 

 saccharina by the presence of dark markings on the 



FIG. 92. Japyx sp., from back. Both saccharina and domestica are common 



California. (Five times in England, and saccharina probably came to this 

 natural size.) 



country from there. 



Machilis (Fig. 95) does not occur in houses, but is more common than 

 Lepisma outdoors. It is to be found under stones, in the soil around the 

 base of tree-trunks, among dead leaves and fallen pine-needles, and at least 

 one species occurs in the sand of sea-beaches. 



FIG. 93. 



FIG. 94. 



FIG. 93. The fish -moth, Lepisma domestica. (After Howard and Marlatt; a little 



larger than natural size.) 

 FIG. 94. Young and adult of Lepisma sp., from California. (Twice natural size.) 



COLLEMBOLA. The springtails, mostly of microscopic size, and wholly 

 unfamiliar to any but persistent explorers of nature, comprise many more 

 species than the Thysanura. Their most distinctive character is the pos- 

 session, by most of them, of the forked spring (Figs. 96 and 97), by 

 means of which they leap vigorously when disturbed. This spring is 



