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BULLETIN OF THE BUREAU OF FISHERIES. 
slow. Yet the Peltodytes larva, when ready to pupate, travels farther from the 
water’s edge than the much larger Cybister or Hydrous larva. 
Leng (1913, p. 35) made a curious statement with reference to these larvae: 
“The larvae of the Haliplidae, Dytiscidae, Hydrophilidae, Gyrinidae, and Parnidae are 
purely aquatic, living wholly in the water, but not swimming.” This applies only 
to the Parnidae and Haliplidae; the others can and do swim. 
The adult beetles can walk, run, jump, swim, and fly with varying ability. Fly- 
ing is the means of locomotion by which they travel from one body of water to 
another and so disseminate their species. The larger species of dytiscids and hydro- 
philids can cover long distances and are sometimes found at night around electric 
lights far removed from any water. Many instances of their capture about these 
lights are recorded by Sherman (1913) in his paper on “Some Habits of the 
Dytiscidae.” Needham in “Fresh-water Biology” (1918, p. 905) said of Hydrous: 
“It is attracted to electric lights in vast numbers in the spring, where it falls 
beneath them and flounders around in the dust of the street. * * * Another 
hydrophilid, which often swarms into trap lanterns set over streams, is Berosus.” 
Yet most of the adults can be safely kept in an open aquarium. Though the gyrinids 
have to climb up on some support above the water before they can spread their 
wings for flight, yet once started, they prove to be strong fliers, for Fall (1901, 
p. 55) has recorded: “I have seen hundreds of Gyrinus consobrinus about the 
electric lights at Riverside (Calif.) in May.” 
The order of excellence in swimming and walking amongst a series of representa- 
tive adult dytiscids has been determined by student classes at Lake Forest for a 
number of years, and, with the addition of jumping, was published in the Ameri- 
can Naturalist (Needham and Williamson, 1907, p. 480). The general conclusion 
that increasing fitness for swimming accompanies increasing unfitness for walking 
and running seems to be well established. Incidentally it may be noted that the 
Gyrinidae show this nearly as well as the Dytiscidae. Swimming with such swift- 
ness and agility that it is almost impossible to catch them without a net, once they 
are removed from the water they prove to be very poor walkers, and can not run 
at all. 
Jumping seems to be a function peculiar to the dytiscids and gyrinids, and so 
far as known is not found at all among the hydrophilids and haliplids. There 
is another dytiscid whose jumping ability exceeds that of Laccophilus maculosus, 
the champion of the Lake Forest tournaments. This is Thermonectes ornaticollis, 
which, when captured in a net, leaps about like a small frog. Another peculiarity, 
not mentioned by Needham and Williamson, is that both Laccophilus and Ther- 
monectes can jump when lying on their backs as well as when right side up. The 
ability to jump is evidently dependent upon the flattening of the hind legs, which 
brings the basal joints into one plane of action, and greatly increases their effi- 
ciency in that plane. To compensate for the lack of ability to jump, all the adult 
hydrophilids and haliplids are good walkers, and many of the former can run with 
agility. 
The relative swimming ability of the dytiscid and the hydrophilid is well shown 
when they come to the surface for fresh air. The hydrophilid swims well but not 
