2 5 6 
Beetles 
philidae) (p. 258) by having slender thread-like antennae instead of clubbed 
ones. All are oval and flatly convex in shape, with hard smooth body-wall, 
usually brownish or black, and when at rest hang head downward from 
the surface of the water, the characteristic breathing attitude. The females 
sometimes have the elytra furrowed with shallow longitudinal grooves, and the 
males of most species have a curious clinging-organ on the expanded first three 
or four tarsal segments of the front feet (Fig. 349). This organ is com¬ 
posed of a hundred or more small capsules on short stems and two or three 
very much larger pads. It is used for holding the females in mating, and 
adheres to their smooth body-wall by the secretion of a gummy fluid insol¬ 
uble in water. The pads and capsules may also act to some extent as 
“suckers’’ by atmospheric pressure. The hind legs are long, strong, 
and flattened to form oars or swimming-organs. This beetle regularly and 
perfectly “feathers its oars” by a dexterous twist while swimming. To 
breathe, the beetle comes to the surface—its body being less dense than 
water, it floats up without effort—and projects the tip of its abdomen through 
the surface film. It now lifts the tips of the elytra slightly; air pours in 
and is held there by the fine hairs on the back, where are also the spiracles, 
or breathing-openings. Thus when the beetle goes down 
again it carries with it a’supply of air by means of which 
respiration can go on for some time under water. The 
diving beetles can be readily kept in aquaria, as can also 
their larvae (described in the next paragraph), and the 
life with the characteristic swimming, 
diving, breathing, captur¬ 
ing of prey, and feeding 
all easily observed. 
The life-history of 
no American species has 
been completely worked 
out, but the eggs of some 
species are dropped ir- 
regularly on the water, 
while those of others are 
laid in slits cut by the 
Fig. 348. —Water-tiger, the larva of the predaceous water- sharp ovipositor of the 
beetle, Dyticus sp. (Natural size.) female in the stems of 
^and^d^^^NaUna^stee!) 4 ^'^ 6 ^ 6 ' ^^ cus s ^’’ aquatic plants. The long, 
slender, semi-transparent, 
predaceous larvae (Fig. 348) are known as water-tigers. They have six slender 
legs and the head is large and flattened. It bears long, slender, curved, 
sharp-pointed, hollow mandibles, each with a small opening at the tip and 
Fig. 348. 
Fig. 349. 
