264 



AN INTRODUCTION TO ENTOMOLOGY 



In the Northern States our native species are usually found in 

 the fields or forests under sticks, stones, or other rubbish. But 

 certain imported species become pests in dwell- 

 ings. In the warmer parts of the country, how- 

 ever, native and foreign species alike swarm in 

 buildings of all kinds, and are very common out 

 of doors. 



Fig. 299. — Ootheca of a 

 cockroach. 



Cockroaches are very general feeders; they destroy nearly all 

 forms of provisions, and injure many other kinds of merchandise. 

 They often deface the covers of cloth-bound books, eating blotches 

 upon them for the sake of the sizing used in their manufacture ; and 

 I have had them eat even the gum from postage stamps. They thrive 

 best in warm, damp situations; in dwellings they prefer the kitchens 

 and laundries, and the neighborhood of steam and water pipes. They 

 are chiefly nocturnal insects. They conceal themselves during the 

 day beneath furniture or the floors, or within the spaces in the walls 

 of a house; and at night they emerge in search of food. The de- 

 pressed form of their bodies enables them to enter small cracks in 

 the floors or walls. 



Not only are these insects very destructive to our possessions, but 

 owing to their fetid odor merely the sight of them awakens disgust ; 

 but it is due them to state that they are said to devoiu* greedily bed- 

 bugs. This will better enable us to abide their presence in our 

 staterooms on ocean voyages, or in our chambers when we are forced 

 to stop at poor hotels. 



The eggs of cockroaches are enclosed in purse-like capsules (Fig. 

 299). These capsules, or oothecse, vary in form in different genera, 

 but are more or less bean-shaped. Within, the ootheca is divided 

 into two parallel spaces, in each of which there is a row of separate 

 chambers, each chamber enclosing an egg. The female often carries 

 an ootheca protruding from the end of the abdomen for several days. 

 It has been found that a single female may produce several oothecse. 



The nymphs resemble the adults except in size, and, 

 in the case of winged species, in the degree of develop- 

 ment of the wings. In adults also of some species the 

 wings are reduced, atrophied, or absent; this condi- 

 tion exists more frequently in females than in males 

 (Fig. 300). 



As in most other insects, the homologies of the 

 wing-veins can be most easily determined by a study 

 of the tracheation of the wings of nymphs; Figure 301 

 will serve to illustrate this. 



Experiments conducted by the Bureau of Ento- 

 mology at Washington have shown that one of the Fig. 300. — A 

 most effective means of ridding premises of cockroaches wingless 

 is dusting the places they frequent with commercial 

 sodium fluorid. Several other substances are used for this purpose; 



