HUNGERFORD: AQUATIC HEMIPTERA. 231 
mediately became silvery. From the behavior of young Corixids, it would 
seem that respiration must take place through the skin for they seldom 
come to the surface, yet in the few experiments tried it was not demon- 
strated that air was taken up in that manner. The nymphs were able to 
survive for many hours in cloth covered jelly glasses submerged in water. 
Number of instars. There are five nymphal instars, which are shown 
on plate XX VI. 
Maturity. This could not be determined from the overwintering 
adults and was overlooked in the summer. The laboratory notes were 
obtained from a start of nine individuals that were placed in a large 
circular aquarium April 3. Seven of these were females. By the last of 
the month there were but three individuals remaining, and May 9 only 
two were left, but first instar nymphs had appeared. Some of these 
changed to second instar nymphs May 12, and reached the fourth instar 
June 2. The two overwintering adults were still alive and laying eggs. 
June 10 found all stages from first instar to the fifth present. June 14 
the first one of the spring generation reached the adult stage, followed 
by another on the 19th. There were still first instar forms present. In 
fact, eggs and newly hatched were present up to July 18. Since the 
overwintering adults were not removed, it is impossible to say whether 
the young represent a second generation or merely a continuation of the 
first. The hot weather of the last week in July brought the rearing to a 
close, and was valuable only in giving all the nymphal instars for study 
and establishing the approximate time for the emergence of the spring 
brood. It is certain that the adults of one year may live to see adults of 
the next. 
Parasitism. In Bool’s Backwater, where this Corixid was found 
throughout the spring in company with the nymphs of Palmacorixa 
buenoi, the infestation of Hydrachnids was heavy. On May 9 a large 
catch of this species showed 85 per cent of the bugs infested with one or 
more mites, some of them with a dozen. May 15 there was not an adult 
to be found that did not bear mites. On June 8 the mites freed them- 
selves from their hosts in the laboratory, and on examination of the in- 
sects in the pond June 11 found the boatmen much less burdened than 
before and almost entirely free June 13. June 18 not a single “mited” 
Corixid was noted. 
DESCRIPTION OF STAGES. 
The following brief description of size and color is given for com- 
parison with P. buenoi of same pond. The structural comparative studies 
of nymphs of various species are reserved for a future paper. 
The Egg. 
Size. Diameter, 0.369 mm.; height, 0.372 mm. 
Shape. Variable, depending on development of embryo within. In 
general ovoid, but with the usual greater convexity of one side. 
Color. Pearly white when first laid, darkening to yellow. There is a 
hexagonal reticulation plain to see under high power and proper lighting. 
