COCKROACHES AND HOUSE ANTS. 89 



LIFE HISTORY. 



The roach in its different stages from egg to adult shows compara- 

 tively little variation in appearance or habits. The young are very 

 much like the adult, except in point of size and in lacking wing-, if 

 the latter be winged in the adult state. In their mode of oviposition 

 they present, however, a very anomalous and peculiar habit. The eggs, 

 instead of being deposited separately, as with most other insects, are 

 brought together within the abdomen of the mother into a hard, horny 

 pod or capsule which often nearly fills the body of the parent. This 

 capsule contains a considerable number of eggs, the number varying 

 in the different species, arranged in two rows, the position of the eggs 

 being indicated on the exterior of the capsule by transverse lateral 

 impressions. When fully formed and 

 charged with eggs the capsule is often 

 partly extruded from the female abdomen 

 and retained in this position sometimes 

 for weeks, or until the young larvae are 

 ready to emerge. The capsule is oval. FlG . 3 9._Egg-ca P suie of Peri P i«neta 



elongate, Or Somewhat beau Shaped, and omerieana: a, side; b, end view-nat- 

 />.,-, . ,-, ,-ry, ural size indicated by outline figure 



one of its edges is usually serrate. The (0 ri<nnai). 

 young are in some instances assisted to 



escape by the parent, who with her feet aids in splitting the capsule 

 on the serrate edge to facilitate their exit. On hatching, it is said, the 

 young are often kept together by the parent and brooded over and 

 cared for, and at least a colony of young will usually be found associated 

 with one or two older individuals. These insects are more or less gre- 

 garious, notably so in the case of the black beetle of Europe and to a 

 less extent with the German and American roaches. 



They pass through a variable number of molts, sometimes as many 

 as seven, the skin splitting along the back and the insects coining out 

 white, soft, but rapidly hardening and assuming the normal color. 

 Some astounding statements have been made as to the length of time 

 required for the development of the roach from the egg to the adult. 

 Four or five years have been said to be necessary for an individual to 

 reach full growth; but more recent breeding experiments have not 

 altogether confirmed these statements. Their development, however, 

 is unquestionably slow, and probably under tin- most favorable condi- 

 tions rarely is more than one generation per year produced. In colder 

 countries the breeding and growth are practically restricted to the 

 warm season. During the winter months they go into concealment 

 and partial hibernation. Ectobia germanica has been shown to reach 

 full growth in a variable period from four and a halt to six months 

 (Hummel, Essaia Entomologiqnes, No. 1, St. Petersburg, 1821 . The 

 common American roach (Periplaneta americana has been carried from 

 the egg to the adult state in our insectary. Young hatching July 11 



