hungerford: aquatic hemiptera. 223 



interest in regard to these early adults is that out of a catch of 29 speci- 

 mens 22 of them were males. If percentage for so small numbers is 

 worth anything it indicates that 79 per cent of those taken at this early 

 emergence were males. 



In a collection made on June 8 were found 33 specimens — 12 fifth in- 

 star nymphs, seven females, and thirteen males. It is worth noting that 

 the mites that had been clinging to the fifth instar nymphs were molting 

 to the free state at this time, just ahead of the time for these nymphs to 

 become adult. June 13 found most of the individuals adult. One nymph 

 in perhaps 200 adults. 



Eggs began to appear about June 20, which was a week later than 

 noted in the laboratory. Most of the eggs had hatched July 11, and in a 

 catch made July 13 there were: 

 4 first instar P. buenoi. 



78 second instar P. buenoi. 



83 third instar P. buenoi. 



18 fourth instar Ai'ctocorixa alternata. 



10 fifth instar Arctocorixa alternata. 

 From this it is seen that to this date the two species have remained 

 separate. These counts were made after the reared material had been 

 studied and both species could be recognized readily. What happened 

 in this pool after this date can not be determined, for no collections were 

 made later than July 19. 



Life Cycle in the Laboratory. 



The development of this species in the various aquaria followed quite 

 closely the changes taking place in nature, being, however, somewhat 

 earlier. 



On April 20, a considerable number of nymphs were brought in from 

 Bool's and placed in a large rectangular aquarium prepared for them. 

 On April 28 two had molted to the next instar, and by May 15 they were 

 all in the fifth instar and doing fine. Up to June 2 this aquarium was 

 kept at a north window in an upstairs room, where no sunlight reached 

 it. Since no adults appeared here, while they were doing so elsewhere, 

 this was moved to a sunnier place outside, with the result that by June 4 

 many had tried to emerge, numbers dying in the attempt. Under labora- 

 tory conditions, molting appears to be a precarious process. 



The first adults to appear during the spring from overwintering 

 nymphs were a male and a female, which died emerging May 11. By 

 May 15 several had made the transition successfully, and it was possible 

 to determine the species presenting this peculiar wintering habit. It 

 will be noted by field notes above that there were no adults in Bool's on 

 May 21, so that those in the greenhouse were brought to maturity earlier 

 than in nature. 



In another aquarium adults began to appear June 5, and were followed 

 the next day by the majority of the others. The first eggs were noted 

 June 13, and were numerous on the sides of the jar June 14, thus estab- 

 lishing a maturation period of about eight days. A similar time is re- 

 quired for incubation. 



