178 
Psyche 
[October 
to take food the day following a meal of two sizeable trout. This 
rather surpised me for I had always supposed Lethocerus would 
kill because of a vicious nature, whether hungry or not. 
Adults likewise would not kill food excepting when they 
were hungry enough to eat what they killed. The adults did not 
feed as often as did the nymphs. It would be expected that the 
adults would not require as much food as the growing nymphs 
but this may not be the only reason for their smaller food re- 
quirement. There may exist here a condition found in the family 
Nepidse. Nepa adults caught afield consistently eat less than 
the adults reared in the laboratory. Two factors perhaps are 
responsible in part or altogether for this condition. The food 
may not suit them as well as what they secure in nature, and 
they were probably used to receiving food less frequently in 
nature. 
On the twentieth of July the nymph died. Since there was 
no indication of any unusual condition in the breeding jar it is 
believed the bug was ready to undergo another molt. As is true 
of insects in general the period of ecdysis is a critical one for 
waterbugs. That this mortality occurs at molting time in nature 
was evidenced by an examination of dead Micro velia nymphs 
taken afield. Measurements of dead nymphs of the several 
instars were made and found to correspond with those of the 
reared specimens just previous to molting time. In addition to 
this specimens were often found in which the skin had already 
split. It would be hard to determine whether the death rate is 
higher with insects reared in captivity or with those reared in 
nature. Hungerford (1919) in discussing the biology of the 
water boatman Palmacorixa huenoi khhoi remarked, ‘‘Under 
laboratory conditions, molting appears to be a precarious pro- 
cess.” I found that to be the case with Ranatra, and it is es- 
pecially true of the later instars. A number of specimens of 
three different species of - Ranatra were isolated for rearing 
purposes, not one of which reached maturity. 
At death the Lethocerus measured as follows : (all measure- 
ments dorsal) : Length along median line 45 mm. ; width of head 
across eyes, 5.5 mm.; width of posterior margin of prothorax, 
13.5 mm.; width across extremities of naesothoracic wing pads, 
