THE APTERYGOTA 



63 



antenna-like projections backward from the end of the abdomen, occur 

 in the Thysanura. Here they are two in number, rather long and con- 

 sisting of many segments, except in a few cases where they have been 

 transformed into a pair. of good sized, unsegmented forceps. In the 

 Collembola, cerci are either entirely absent or very small and consist 

 of only one segment. 



THE THYSANURA 



The Thysanura average much larger than the Collembola. They are 

 characterized as: 



Apterygota with styli on the underside of the abdomen, and with usually 

 long, many-segmented cerci at the end of the body, except in a few species 

 where these have become a pair of forceps. 



Only one Thysanuran is of particular eco- 

 nomic importance in the United States; the 

 Silver Fish or "Slicker" (Fig. 35). 



The Silver Fish (Lepisma saccharina L.). 

 This little household pest is found both in 

 Europe and this country. It is silvery gray in 

 color, usually less than half an inch long, and 

 very active and hard to catch. Besides the two 

 long cerci at the hinder end of the body it has a 

 similar " caudal filament" giving the insect the 

 appearance of having three "tails." It prefers 

 dark places and feeds on book bindings, 

 starched clothing, or anything containing starch, 

 and often loosens wall paper by feeding on the 

 starch used to paste it to the wall. 



It may be controlled by placing on pieces of 

 card, starch paste made as follows: Flour 1 



pint; Arsenic % to % oz.; water enough to make a thin paste after 

 boiling. Spread this on the cards and place near where the insects are 

 found, for them to feed upon. Do not place the cards where young 

 children can get at them. The Silver Fish prefers moist to dry places, 

 so clothing should not be stored where it is damp. Sometimes Insect 

 Powder dusted in the haunts of this pest is helpful. 



THE COLLEMBOLA 



The Collembola are usually very small insects, and being dark colored, 

 in most cases are not often noticed. Most of this group have a "spring" 

 attached near the hinder end of the body beneath. This consists of a 

 single piece to which a pair of others are joined and the whole is carried 

 pointing forward when not in use (Fig. 36). When the spring is suddenly 

 pressed against the ground, the entire body of the insect is thrown into the 

 air and a peculiar hopping or leaping motion results. 



FIG. 35. Silver Fish 

 (Lepisma saccharina L.) 

 about twice natural size. 

 (After 14th Rept. Minn. 

 State Entomologist.) 



