WATER BEETLES IN RELATION TO PONDFISH CULTURE. 
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The antennae extend obliquely outward and backward beneath the first and second legs ; the maxillae 
extend to about the center of the second legs; the labial palpi are longer, reaching the posterior margin 
of the second legs. 
The femora of the first two pairs of legs are at right angles to the body axis, and the tibiae and tarsi 
extend obliquely inward and backward to meet on the mid line. The third legs are similarly arranged, 
except that the femora are pulled so far forward as to become diagonal to the body axis. 
There are large branches on the third legs for the spines at the distal ends of the tibise. 
The pupa is not very active in the pupal chamber and spends much of the time lying on its side. 
However, the normal position seems to be with the dorsal side uppermost and the body strongly arched. 
Of 10 pupae reared to the adult stage 7 emerged 4 days after pupation, 2 five days after, and 1 six 
days after. 
Habits of the adult . — The adult beetle swims rapidly and with considerable agility, the tarsi of the 
hind legs being especially well armed with swimming setae. When captured in the net, it proves to 
be a good jumper, but can not equal Laccophilus and Thermonectes. On the land it can not lift its 
body clear of the ground, and hence flounders around rather helplessly. The only food that any of the 
adults were seen to eat was the nymphs of damselflies, but it is almost certain that their diet is not con- 
fined to these. 
Description of the adult . — General shape an elongated oval, broadest anteriorly, the dorsal surface 
subconvex; total length 7 mm., width 4 mm. 
The head, thorax, and entire under surface of the body are reddish-brown, the reddish tinge rather 
brighter in the male. The vertex of the head is black, and the prothorax has a narrow black line across 
the base and apex. The apical line stops on either side at about the center of the eye and does not reach 
the lateral margin. The basal line is only half the width of the thorax and is slightly enlarged at either 
end. The elytra are dark brown with numerous very small pale yellow markings. The basal portion 
of the elytra in the female is not as shiny as in the male and is sculptured with short and indistinct 
striae. 
The antennae are 11-jointed, joints about equal; the mandibles have a rounded tooth on the dorsal 
surface of the inner margin near the tip and a fringe of short bristles behind the tooth. In the maxillae 
the palps are four-jointed and subclavate, the terminal joint distinctly notched at the tip. The labial 
palps are also notched at the tip, but the notch can be seen only in side view. The prosternum is keeled 
along the mid line and the process it gives off is swollen through the center. 
In the male the first three joints of the tarsus in the two anterior pairs of legs are slightly dilated and 
furnished with a dense fringe of stiff hairs along the lateral margins, each hair tipped with a minute 
disk. The ventral surfaces of these joints are covered with scattered disks, somewhat larger, each at 
the tip of a long stalk whose diameter equals that of the disk. On the sides of the stalks and around 
the margins of the disks are a few minute hairs. The tarsal claws are equal and so tightly appressed 
laterally that they often appear as one; those on the front feet are long and emarginate at the base. The 
hind legs are well developed, the femora with small lamina at the apex and the tarsi lobed externally. 
Genus CYBISTER Curtis. 
Cybister (Curtis, 1827, p. 151). 
This is a genus of large beetles considered the highest and most completely 
developed of the dytiscids. Both the adults and the larvae are voracious and will 
destroy young fish whenever opportunity offers. They have broad and powerful 
hind legs and are strong swimmers; the hind claws are very unequal, the inner 
one being obsolete or wholly wanting. In the males the front tarsi are strongly 
dilated and bear four rows of disks. 
Cybister fimbriolatus Say. Figures 23-33, 51. 
Cybister fimbriolatus (Say, 1825, p. 91). 
Cybister fimbriolatus (Sharp, 1882, p. 715). 
Cybister fimbriolatus (Dugfes, 1885, p. 26; pi. 2). 
Eggs . — Deposited singly in slits made in the stems of rushes, cat-tails, arrowhead, etc. The eggs 
hatch in six to eight days. 
48790°— 23 4 
