BIOLOGY OF PARACOPIDOSOMOPSIS. 



293 



that was discovered in studying the broods of Copidosoma. 

 Only four out of a total of 162 broods gave evidence suggesting 

 that a differential division might have occurred during the 

 segmentation of the egg. It was therefore evident that if such 

 differential divisions do occur in these parasitic insects, it must 

 be studied in a species in which the polyembryonic brood is 

 much larger than that of Copidosoma. For it is clear that the 

 larger the brood the greater must be the number of cell divisions 

 in that period of development at the close of which each blasto- 

 mere becomes the progenitor of an embryo, and consequently, 

 the greater the opportunity for a differential division to occur, 



II. DATA ON SEXES OF PARACOPIDOSOMOPSIS. 



At Austin such a species is found in Paracopidosomopsis 

 floridanus Ashmead, a form very similar to the European chalcid, 

 Litomastix truncatellus, upon which Silvestri worked. This 



TABLE I. 



MIXED BROODS OF Copidosoma. 



little parasite lays its egg in the egg of the common cabbage 

 looper, Autographra brassictz. This species is very favorable 

 for study, and can be reared in the laboratory. Upon con- 

 suming the contents of the Autographra larva, the larval parasites 

 pupate within the skin of the host, forming the typical mum- 

 mified carcass. During the last two seasons about two hundred 

 carcasses have been collected from the field. The silken cocoons 

 were removed from these, after which each was placed in a vial, 

 which was closed with a loose plug of cotton. Under these 

 conditions the parasites readily emerge. 



One hundred and twenty-nine of these broods, taken at random, 



