20 MISCELLANEOUS RESULTS OF WORK OF BUREAU IX. 



dark slaty blue, while the females are lighter and have yellow 

 markings. 



The period of incubation in this species is long, between fifty-six 

 and ninety-three days, according to the varying results obtained. 

 As no individuals were secured in copula, the exact time of its dura- 

 tion was not recorded. The deA T elopment of the eggs may be watched 

 from the exterior. The females should be treated very carefully, 

 but with a lens one may see on the ventral side, in the marsupium, 

 the distinct form of the eggs, and may notice the increase in size 

 and finally note the young embiwos and the little white young. One 

 experiment with 10 females was most fruitful in giving data on this 

 point. On May 8, June 16, and July 8 young had been produced, 

 and on examination on July 26 all were found to be unfertilized 

 except one. which had eggs apparent. On August 7 the fertile 

 female produced a brood of young. This was ninety-three days 

 after being placed in captivity. A male was admitted on July 26, 

 and on September HO a brood of young was produced. This would in- 

 dicate a period of incubation of, at the most, sixty-eight days. In 

 another experiment a female which had just produced a brood of 

 young was placed with 3 males on August 7. On October 2 a brood 

 of young was produced, making the period of incubation fifty-seven 

 days. The number of young in a brood varied from 21) to 79. 



The little isopods are pure white when they leave the marsupium. 

 They have six pairs of legs. Within twenty-four hours of birth they 

 molt, and still have only six pairs of legs. Between the fourteenth 

 and eighteenth days another molt takes place and the resulting 

 third instar has seven pairs of legs. The young continue to grow 

 and molt, having been observed in the act of molting on the twenty- 

 eighth, thirty-sixth, fifty-eighth, and sixty-eighth days. After the 

 first molt there is no regularity as to times of molting in the brood, 

 all depending on the food supply. After the first molt a slight dark- 

 ening of the intestines is noted, and by the twenty-first day the sow- 

 bugs are of a gray color throughout and under 3 mm. in length. In 

 fifty-eight days they have not increased beyond 4 mm. in length. The 

 greatest size of any found was 15 mm. This specimen was probably 

 several years old. Females not over 7 mm. long are capable of 

 reproduction. 



Before molting, the body of all sowbugs becomes a very dirty 

 gray color. The act of molting is peculiar. At first a white border 

 indicating the loosening of the old skin appears at the front edge 

 of the fifth free thoracic segment, then another on the sixth, and 

 still another on the seventh. Finally the entire posterior half of the 

 skin is free and the isopod steps out of it. This process consumes 

 about twenty-four hours, and when completed the posterior part 

 of the body is of fresh slate color, while the'old anterior part appears 



