258 PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 



something like 275 separate but similar experiments in their repro- 

 duction in confinement in the laboratory. It is of course possible 

 since it was especially desired to continue the experiments as long 

 as possible with individuals of known parentage, that the results are 

 misleading. Possibly had American Trichogramma been collected 

 in the open from a variety of sources, a race might have been found 

 which was thelyotokous even as the similar search might have 

 resulted in the discovery of an arrhenotokous race in Europe. As it 

 is, the American stock was once renewed. In 1907 a series of experi- 

 ments was conducted with parent stock reared from brown-tail moth 

 eggs collected in Maine ; and in 1908 a similar but more extensive 

 series with parent stock from eggs of the brown-tail moth collected 

 in Massachusetts. In each instance the results were the same. 



The longest series of experiments with the thelyotokous Euro- 

 pean race was with the progeny of individuals reared from one lot 

 of European eggs from the Province of Carniola, Austria. Similar 

 experiments with one other lot of females upon another shipment 

 of eggs from the same Austrian province and perhaps from the same 

 locality resulted similarly, but the series was not nearly so long. In 

 the first-mentioned series 13 generations were reared in the laboratory, 

 all but the first three being parthenogenetic. Males were secured 

 at one time, and for a limited number of generations, but soon dis- 

 appeared, even from the progeny of mated females. The results 

 of these experiments will be published in detail later. 



Importations of egg masses of the brown-tail moth which had been 

 collected in the open in Europe were first attempted in the summer of 

 1906, and from almost the first of those which were received at the 

 laboratory a few examples of the pretiosa-like European form were 

 reared. Mr. Titus attempted to secure reproduction in the labora- 

 tory that first season, but as he had no supply of host eggs in which 

 embryonic development was not considerably advanced, his attempts 

 met with failure. 



In 1908 a larger number of egg masses of the brown-tail moth was 

 imported from a great variety of European localities, and as before, 

 the p7"etiosa-like Trichogramma was quickly secured. The failure 

 of the previous season and its cause had early been taken into ac- 

 count, and some time before a large quantity of fresh eggs of the 

 brown-tail moth had been collected and stored at a temperature 

 sufficiently low to prevent embryological development. When sup- 

 plied with a quantity of these eggs the imported Trichogramma ovi- 

 posited with the greatest freedom, and in the course of a few genera- 

 tions had increased enormously, so that many thousands were lib- 

 erated later in the fall. It was conclusively demonstrated that 

 even though the host eggs were dead, abundant reproduction could 

 be easily obtained under laboratory conditions. 



