58 IOWA STUDIES IN NATURAL HISTORY 
larval stage in the laboratory manifested no interest in food for 
some time. Even after they manifested hunger by seizing and 
eating bits of meat or other food held before them, the young 
adults manifested less eagerness for food and less regularity in 
their feeding reactions than did the larvae. 
On July 26, a large number of late larvae and young adults 
of the larger type were brought into the laboratory. Twenty 
animals, including young adults and larvae which had almost 
attained the adult condition, were retained for experimental 
study. During several days following July 26 none of them 
manifested any interest in food. On August 3 nearly all of them 
manifested hunger by promptly seizing and eating crayfish’s 
meat held before them or of approaching bits of it held some 
distance from them. 
Like the late larvae, the young adults demonstrate an ‘‘ap- 
proaching’’ and a ‘‘seizing’’ reaction. Sometimes they exhib- 
it a type of reaction which might be interpreted as the ‘‘nos- 
ing’’ reaction described by Copeland in Diemyctylus virides- 
cens. More commonly, however, the seizing reaction follows 
the approaching reaction without an intervening pause. On 
the other hand, many of the animals would at times attempt 
to seize objects held close to them without first manifesting an 
approaching reaction even though they would not approach an 
object held a short distance from them. When the seizing re- 
action is not preceded by the approaching reaction an initial 
response similar to the nosing reaction may be observed in some 
instances, while in others the seizing reaction is apparently the 
initial response. 
Obviously the sense of sight is an important factor in these 
reactions; however, that the olfactory sense also plays an im- 
portant part in the feeding reactions is demonstrated by the 
following observations. A packet of gauze containing a bit of 
crayfish’s meat and another containing a small piece of rock 
were suspended by threads in the presence of several of these 
hungry animals. They promptly seized the packet containing 
the crayfish’s meat as often as it was presented, but made no 
attempt to seize the other packet. Two packets of gauze, one 
of which contained frog’s meat, the other dry cotton, were now 
- suspended by threads in the presence of the same animals. They 
promptly seized the packet containing the frog’s meat as often 
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