BIOLOGY OF PARACOPIDOSOMOPSIS. 3OI 



IV. EXPERIMENTAL AND CYTOLOGICAL STUDIES. 



If any one of these forms of abnormal behavior of sex chromo- 

 somes does occur in the cleavage divisions of Paracopidosomopsis, 

 it should be possible to detect it by experimental and cytological 

 studies. We have undertaken both lines of investigation, and 

 already sufficient progress has been made to clear up certain 

 points. 



The experimental work has been greatly interfered with by 

 the ravages of the so-called wilt disease, to which the Auto- 

 graphra larvae are extremely susceptible under laboratory con- 

 ditions. In all of the experimental work the precaution has 

 been taken to protect the moth eggs from being parasitized before 

 beginning any experiment with them. This has been done 

 by having the moth lay its eggs under a bell-jar from which all 

 parasites were scrupulously excluded. Furthermore, the para- 

 sitized eggs and the young larvae developing from them have 

 been similarly protected. In all experiments the female parasite 

 has been permitted to make but one oviposition in each moth egg. 



The first set of experiments were undertaken with a view to 

 determine whether the fertilized female parasite could lay eggs 

 which produce males and females. In one experiment 23 moth 

 eggs w r ere parasitized by fertilized females. Sixteen larvae 

 hatched three days later. Of these two reached full growth. 

 One of the two larvae was not parasitized, and formed a pupa 

 from which a moth later emerged. The other was transformed 

 into a typical mummified carcass, from which a brood of para- 

 sites in due time emerged. The brood contained 2,096 indivi- 

 duals, of which 1,889 were females and 207 males. While these 

 results are meager, nevertheless they indicate clearly that a 

 fertilized female is capable of laying eggs from which indi- 

 viduals of both sexes develop. In this instance it is not possible 

 to tell whether the mixed brood came from one egg or from two 

 eggs, since there was no way of determining the number of eggs 

 deposited by the parasite in the egg of the host at the time she 

 made the oviposition. 



In another set of experiments unfertilized females were used. 

 In one experiment eighty moth eggs were parasitized, each by 

 one oviposition by an unfertilized female. Sixty-six larvae 



