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BULLETIN OF THE BUREAU OF FISHERIES. 
The writer (Wilson, 1923) has recorded the killing of a young buffalofish in 
an aquarium at Fairport, Iowa, by a female Hydrous triangularis just after she had 
completed spinning an egg case. 
None of these accounts are very convincing. If the neighbor mentioned by 
Elies had actually seen a beetle killing his goldfish fry, there was no need of further 
proof. If he had not, the placing of the two together in a basin of water with the 
resultant death of the fish certainly did not furnish such proof. There are large 
water bugs belonging to the family Belostomidae which are just as likely to kill 
young carp as are the two beetle genera mentioned by Riley. Garman’s state- 
ment is a general one without the citation of anything to prove its validity. The 
writer, in his record above cited, called attention to the fact that the con- 
ditions under which the killing of the buffalofish occurred were artificial and 
abnormal. Consequently, while it is highly probable that these large beetles do 
sometimes kill small fish, we have to admit in all fairness that their guilt has not 
yet been legally established. It is also worthy of record that while Cybister and 
Dytiscus and Hydrous are common in nearly all the fishponds at Fairport, no one 
has ever seen an adult beetle attacking one of the fish fry. 
FISH AS BEETLE EATERS. 
Having ascertained how many and what species of beetle larvae and adults 
prey upon fish fry, we may turn about and inquire what kinds of fish ordinarily eat 
beetle food. Our inquiry now is much more easily answered, since it does not 
involve any watching of the fish. We have simply to examine the contents of the 
fish’s digestive canal to obtain exact information both as to the quality and the 
quantity of food consumed. Moreover, the beetles eaten are more readily recog- 
nized than almost any other kind of food. The hard chitin covering of the head of 
the beetle larva, together with the antennae and mouth parts, remain sufficiently 
intact to be readily recognized. For the adults the entire beetle is sometimes practi- 
cally uninjured and may even make a respectable specimen after a temporary 
sojourn inside a fish’s stomach. In case it is mutilated, there is always enough of 
the hard chitin parts to render identification easy and certain. 
EVIDENCE FROM FISH BAIT. 
So far as known neither the beetle larvae nor the adults are used anywhere in 
the United States as fish bait, but there is apparently no reason why they would 
not make excellent bait. The larva of the horned Corydalis or dobsonfly ( Corydalis 
cornuta) is known to fishermen everywhere as the dobson, crawler, and a variety 
of other names and is much prized as fish bait, especially for black bass. 
The larva of Hydrous triangularis closely resembles the dobson in size and general 
appearance, and it is greedily eaten by bass whenever offered to them. Large- 
mouthed black bass are used in many of the experiments at Fairport, and there are 
some of them in the tanks most of the time. Hydrous larvae of all sizes up to full 
development have been fed to these fish during the summer. They have always 
eaten the larvae with great avidity, and if they were hungry it sometimes seemed 
as if the larva did not fairly strike the surface of the water before it was snapped 
