COCKROACHES 133 



average of about eight for each one, before they died. 

 The twenty-five capsules were deposited between April 

 20th and September 6th of the same season. 



Often the egg-case is not deposited free from the ab- 

 domen at once, but is carried about by the female with the 

 end of the capsule projecting from the posterior end of 

 the body (Plate II). C. V. Riley has said that "The 

 female cockroach carries the egg-case about with her until 

 the young are ready to emerge, when it is dropped." Other 

 observers have found that the egg-cases are not carried 

 by the female more than four or five days at the most. 

 Butler says : " When full the case protrudes from the end 

 of the abdomen of the female, and is carried about by her 

 in this position for about a week, after which it is dropped 

 into a suitable crevice in a warm situation." 



The observer, Hummel, who watched the life history 

 of the German cockroach, says that the young molted six 

 times before becoming full-grown and that they spent 

 from three to five months or even longer in completing 

 their growth. When the nymphs first shed their skins 

 they are soft and whitish in color, but soon harden and 

 change to a darker color. He also states that the mother 

 sometimes assists the young to escape from the egg-case 

 by tearing it open with her jaws, thus providing a means 

 of egress for the young. 



Marlatt says that the common American roach (Peri- 

 planeta americana) has been carried from the egg to the 

 adult state in the Insectary at Washington and that the 

 young which hatched July 11 reached their full growth 

 between March 14 and June 12 of the following year. In 

 this case, then, nearly twelve months were needed to 

 attain the adult stage. 



