Thigmokinesis
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Psephenus herricki
Herrick's Water Penny Beetle
Psephenus herricki is a water penny beetle found in eastern North America. Larvae are highly flattened and inhabit stream riffles, where they occupy interstitial crevices and undersides of stones. The species exhibits specific behavioral and morphological adaptations to flowing water environments, including thigmokinesis that inhibits movement when wedged in substrate. Adults are associated with wave-splashed rocks that serve as mating sites and oviposition substrates.