August, '13] HOLLOWAY: METHODS WITH MINUTE HYMENOPTERA 343 



insects from one tube to another will be described below. In placing 

 the parasites with fresh eggs the males may be left out of considera- 

 tion. In a tube where the females are ovipositing the males walk about 

 aimlessly and do not disturb the females. The important thing is to 

 get some females in the tube with the fresh eggs. The females of 

 Trichogramma may easily be distinguished by the antennae, though 

 the living individuals usually move so rapidly that it is difficult to 

 determine the sex in any way whatever. The action of the different 

 sexes in the presence of the fresh eggs is positive evidence, however. 

 While the males will pay no attention to the eggs, the females — as 

 soon as they have become accustomed to their new location — will 

 busily examine a number of the eggs, crawling over them and tapping 

 them with the antennae, and finally selecting some for oviposition. 

 One egg after another will then be parasitized. The writer found it 

 most convenient to place two or three females in a tube containing 

 about fifty eggs. One female to about twenty-five host eggs may be 

 correct. 



In transferring the parasites from one tube to another, it was found 

 best to place the tubes on a smooth white surface so that the insects 

 might easily be observed. A plate of glass five by seven inches, "with 

 a piece of white paper glued to the underside, was used for this purpose. 

 The plate of glass was placed on a table before the worker. At the 

 worker's right hand was a very fine camel's hair brush, a fine insect 

 pin, and a watch glass containing the sugar solution. The parasite 

 tubes were placed at the left of the worker. A few parasites were al- 

 lowed to come out on the glass plate, and they were then made to walk 

 or jump into the proper tube, which was held open before them. If 

 necessary, the parasites were touched ver-y slightly with the camel's 

 hair brush so as to make them go in the right direction. Occasionally, 

 a parasite would escape, but after the operator acquired some experi- 

 ence there was little loss. 



Another way to transfer the parasites from tube to tube is to open 

 the two tubes and hold them mouth to mouth. The tubes should be 

 of the same size, and the mouths should be held firmly together. If 

 there are a large number of parasites in one of the tubes, however, too 

 many will usually go into the new tube. In this work advantage should 

 be taken of the fact that the parasites will ordinarily go toward the 

 source of light. The tubes should be arranged so that the parasites 

 will proceed from the old tube to the new one in the direction from 

 which the light comes. 



The tubes should be kept in a suitable tray on a piece of white paper, 

 so that the parasites may be observed. A small label bearing a num- 



