Notes on the Behavior of Dineutes Americanus

Abstract

A study of Movement :--These beetles swim by means of the meso-and metathoracic legs, which are so modified as to be almost useless for land locomotion. While on the water D. americanus exhibits perfect mobility and ease in swimming, on land it turns to an awkward crawl, pulling itself along by the long forelegs, tilting from side to side as the heavy unsupported body is dragged across the uneven ground. Usually, however, when off the water surface, the body is supported only by the front legs.When about to swim the beetle extends the middle and hind legs laterally, like a pair of oars They are then brought smartly down to the caudal axis, which is their usual position at rest. The forelegs are fitted into the grooves in the sternal plate adapted to receive them or they may be extended on the surface film. Sometimes they are used for cleaning the body or to assist in the process of feeding. Because of the grooves in the sterna the legs can be withdrawn and the body then presents a perfect "stream-

Distribution, Coexistence, and Competition of Whirligig Beetles

“…The total numbers taken at each of the censuses (shown at the top of each histogram in Figs 6, 7, and 8) offer an approximate indication of the changes in population size occurring through the spring and summer. This trend is the same in all three ponds and agrees with' the seasonal trend of population size recorded by Smith (1926) for a Massachusetts pond containing mostly D. assimilis (= americanus) and a few D.…”

The New World whirligig beetles of the genus Dineutus Macleay, 1825 (Coleoptera, Gyrinidae, Gyrininae, Dineutini)

“…The juvenile stages have been formally described and illustrated by Wilson (1923) and sparse life history information is available in Smith (1926) and Istock (1966; 1967). …”

“…Hatch (1925a) described briefly the life history of several common North American species, with much of the data being summarized from other sources. Smith (1926) also added some life history information on Dineutus assimilis in his note on behavior, but this was mostly anecdotal. Istock (1966) briefly describes some life history elements for Dineutus assimilis , Dineutus hornii , and Dineutus nigrior , including adult and larval durations for Dineutus nigrior and Dineutus hornii , later (1967) adding anecdotal pupal information for the later two species, but this was not the focus of Istock’s studies.…”