2 J. T. PATTERSON 



ology of these insects which are as yet obscure, and there is still 

 to be written a complete account of a single representative 

 species. It is highly to be desired that a description be given 

 of the development of a typical species in each of the three fami- 

 lies of parasitic hymenoptera in which polyembryony has been 

 reported. The evidence, although fragmentary in many instances, 

 clearly indicates that there are significant differences in the type 

 of development in each of the three famihes. 



This paper is an attempt to give an account of each of the 

 more important steps in the embryology of the egg up to the 

 point at which the sexual embryos are formed. For this pur- 

 pose I have selected a representative of the family Chalcididae. 

 The species used is Paracopidosomopsis fioridanus. Ashmead. 

 It was chosen primarily because of the ease with which it can 

 be secured in this vicinity^ and because it can be reared readily 

 under laboratory conditions. In studying the development of 

 parasitic forms, the latter advantage cannot be over emphasized; 

 for if the work is to be free from suspicion, one must scrupu- 

 lously avoid the possibility of the host eggs becoming infected 

 with foreign parasites. This can only be done when the material 

 used is reared under laboratory conditions. Another reason for 

 studying Paracopidosomopsis is the fact that non-viable larvae 

 appear in the polygerm stages of this species. These are similar 

 to, if not identical with, the asexual larvae of Litomastix. 



1 shall first give a brief resume of the life-history of Paracopi- 

 dosomopsis, as it will then be easier to follow the account of 

 the development of the egg. The parasite lays its egg in the egg 

 of the common cabbage looper, Autographra brassicae. The two 

 eggs develop simultaneously, and, as is the case in several other 

 species, there is one generation of the parasite for each generation 

 of the moth. The moth reaches its complete development several 

 days before the parasites, but is not ready to lay its eggs until the 

 parasites emerge. I have not been able to determine the number 

 of generations per year for the Austin region. The looper is 



2 I am deeply indebted to Mr. Thomas H. Jones, of Baton Rouge, La., for 

 sending me parasitized carcasses at times when they could not be found here 

 at Austin, 



