366 THE GYPSY MOTH. 



circumstances, but all at the normal out-door temperature. 

 Some were kept covered with cheese cloth, others with the 

 regular box covers, and still others were kept covered a 

 part of the time with the covers and the rest of the time 

 with cheese cloth. One hundred and sixty of these pupas 

 were from larvae raised in confinement, while the rest were 

 collected in the field. Two hundred and thirty-three moths 

 emerged and laid their eggs, but without that regularity 

 that characterizes the egg-clusters of fertilized females. 

 Most of the females laid a considerable number of eggs, 

 though four laid no eggs but deposited some of their hair ; 

 one laid only a single egg, while two other females laid four 

 and five eggs respectively. The boxes containing these eggs 

 were kept under the same conditions as other boxes which 

 contained fertile eggs, which hatched at the usual time in 

 the spring ; but no trace of embryonic development could 

 l)e discovered within them during the fall, and they were 

 again critically examined the last of January, 1894, when 

 they were found to be more or less shrunken, and showed 

 no sign of an embryo within, as is the case with fertile eggs. 

 Early in the spring a piece of glass was glued over the top 

 of each box, so that the young caterpillars could not escape, 

 should any of the eggs hatch. They were daily inspected 

 till after the time when they should have hatched, and then 

 once a week till July, and less frequently till October, 1894, 

 but not an egg hatched. While this experiment does not 

 prove that parthenogenesis does not sometimes occur in the 

 gypsy moth, it would seem to indicate that it is probably 

 of rare occurrence. A few cases have been reported in 

 Europe. Carlier states that he has seen three generations 

 without mating having taken place, but the last genera- 

 tion gave only males. Siebold, who refers to this case 

 in " Entomologische Zeitung, Stettin," Vol. XXH, page 

 443, expresses some doubt, since no exact account of events 

 was given. Weijnbergh, however, has given a very com- 

 plete account of breeding this species from unfertilized 

 eo-o-g for three generations, until, at last, the eggs dried 

 and brought his observations to a close. Dohrn, who 

 reports this case in "Entomologische Zeitung, Stettin," 

 Vol. XXXn, page 30, expresses the opinion that the dry- 



