COCKROACHES 375 



When numerous they congregate, especially in kitchens where it is warm, 

 damp, and not overly clean. On shipboard they often abound to such an 

 extent as to cause much damage, in some cases entire supplies of certain 

 foods being spoiled by eating, or rendered nauseous by their contact, a 

 disagreeable odor being imparted by secretions from certain scent-glands 

 situated in the bodies of the insects. The readiness with which they are 

 transported with food supplies make their introduction into military 

 and other camps a matter of great probability, and when once infested, 

 such places are soon thoroughly stocked with these skulking creatures. 



BIOLOGY 



The life histories of our household roaches are very similar. The eggs 

 are deposited incased in an oblong, leathery pod, called an ootheca, and 

 containing several eggs each, arranged in two longitudinal rows. In some 

 cases this ootheca is carried around for some time by the mother roach, 

 partially protruding from the tip of the abdomen. But generally they are 

 deposited in some cranny and sometimes the ootheca of Periplaneta is 

 glued in folds of clothing, or in a leaf if of outdoor occurrence, and 

 covered over with bits of material chewed oiF by the insect. I have myself 

 seen instances of this, once on a garment and twice on leaves, and the 

 recognition of the ootheca in such cases is not at all clear until it is 

 uncovered. 



When first hatched from the egg the young roach resembles the adult 

 in general form, but is apterous and the body is soft and whitish in color. 

 Soon, however, the chitin becomes oxidized and the normal color appears. 

 A number of molts occur during growth, the old skin splitting along the 

 dorsal line of the thorax, and through this slit the insect emerges, the 

 process being one requiring some considerable exertion; every part of 

 the body sheds its old covering, antennae, feet and all. The freshly molted 

 roach, like one newly hatched, is whitish in color, but a few hours serve 

 to restore the natural colors. In the last two instars the wings appear in 

 a rudimentary condition, at the last molt appearing fully developed. 

 This appearance of rudimentary wings is the only character separating 

 the stages of the roach which correspond to larva and pupa of insects 

 with complete metamorphoses. The terms larva and pupa are not gen- 

 erally applied to insects with incomplete metamorphoses, the term nymph 

 being there used, the degree of development being indicated by the number 

 of the instar, or period between two molts. A single roach may produce 

 several egg-masses in a season, and in the common house species the period 

 of development from egg to adult varies with the food supply, climatic 

 conditions, etc. 



While in some tropical and subtropical regions certain species of 



