CROSSING EUSCHISTTJS VAHIOLAKIUS AND EU8CHISTUS SERVUS. 351 



immediately after reaching the winged stage. Five of the ma\e servus used 

 in these experiments were raised in our laboratory, and like the variolarius 

 females, were transferred to the experiment cages immediately after reaching 

 the winged stage. The other 9 males were wild specimens, received from 

 North Carolina. These experiments were continued for nearly two months, 

 and no mating occurred at any time. The experiments were not closed until 

 many mifertilized eggs had been deposited in all the cages *. 



Possibly nymphs captured in the field, and raised to maturity in the 

 laboratory may be more easily bred from; but in our experience we have 

 never been able to collect the wild nymphs early enough in the season to 

 succeed in breeding them with each other, or with an alien species. 



The reciprocal cross with the first generation ( $ servus & ^ variolarius) 

 also proved unsuccessful ;' these experiments, as in all other cases, beino- 

 continued until unfertilized eggs had been deposited a number of times in 

 each caoe. 



We believe our lack of success in these cross-breeding experiments was not 

 wholly due to the fact that the males and females were of diiferent species, 

 for we were almost as unsuccessful in getting a second generation of pure 

 variolarius, though we had much better success in raising the second genera- 

 tion from servus. The first generation of this species mated from 10 to 18 

 days after they reached the winged stage, and were very fertile. 



Fortunately for the success of our cross-breeding experiments, the F 

 hybrids resembled servus and not variolarius, in that most of them mated 

 readily in captivity, from 10 to 20 days after the last moult, and like the 

 first generation of servus proved to be very fertile. 



The following experiments show it is much more difficult to get a second 

 generation from variolarius tiie same season, although the first generation, 

 if kept through the winter, will normally mate and deposit eggs early in 

 the spring. 



In 1911 we experimented with a few pairs of young variolarius, all reared 

 from the same batch of eggs. About twenty days after they had reached the 

 winged stage, a few males and females were placed in the same cage, from 

 August 6th to August 27th. During this period they did not mate once, 

 though the females deposited unfertilized eggs, and dissection showed the 

 males to be apparently sexually mature. Two females and four males from 

 this same batch of eggs were carried through the following winter^ and in 



* As a rule unfertilized eggs are deposited quite differently from those that have been 

 fertilized. The latter are deposited in flat, symmetrical groups containing sometimes more 

 than 30 eggs, and all adhering together. Unfertilized eggs, on the contrary, are dropped 

 here and there on leaves, grasses or herries, sometimes only one or two eggs at a time, or 

 more frequently in groups of three, four, or five. We never destroyed the unfertilized eggs 

 until ten days after their deposition, although fertilized eggs always show the initial staoes 

 of development on the 3rd or 4th day. 



