Ecology of the Water Penny Beetle Psephenus herricki (DeKay)
1971
Murvosh, Chad M.
A general theory of distribution suggests that the microhabitat, habitat, and geographic distribution of Psephenus herricki is related to water turbulence. The different life stages typically occur in stream riffles. Adults are found in riffles because they are "attracted" to the moist wave—splashed rocks that stick out of the water. These same rocks provide a mating site and give the female access to the subsurface materials for oviposition. The microdistribution of eggs is a function of the distribution of wave—splashed rocks during oviposition and female oviposition behavior. Oviposition initially accounts for the large numbers of larvae in riffles, but larvae live about 2 years giving them sufficient time to disperse into the runs and pools. Dispersion, however, is negligible due to a thigmokinesis that inhibits vagility when they are wedged in the interstitial spaces of the substrate. This and the distribution of algae on rocks seems to determine the microdistribution of larvae. Riffles contain an abundance of these interstitial crevices due to sorting by stream turbulence. Turbulence and physiography, governing the geographic distribution of riffles, directly influence the geographic distribution of the species.
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