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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 ina 
catch made July 13 there were: 
4 first instar P. buenoi. 
78 second instar P. buenoi. 
83 third instar P. buenoi. 
18 fourth instar Arctocorixa 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 dving 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. 
