What Bug Is That? The guide to Australian insect families.

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Psephenidae

Overview

Larval psephenids are commonly found adhering to rocks in streams throughout the wetter parts of eastern Australia, but one species has also been recorded from the George Gill Ranges in the central part of the continent. Larvae feed on algae covering rocks, and because of their unique, streamlined form, they are able to move across surfaces within high energy water flows and thus exploit resources unavailable to their competitors. Pupation takes place within the larval skin in concealed areas along the stream bank. Adults are very cryptic, but they have been observed flying above streams on hot days. [Davis 1986; Hinton 1955, 1966.]

Description

Broadly oval, flattened beetles clothed with short, dense pubescence forming pattern which is superimposed on maculate dorsal surface. Head deflexed and only partly visible from above within anterior pronotal emargination, and bases of pronotum, scutellum and elytra finely crenulate forming  interlocking device. Head narrowed anteriorly forming a short rostrum; mouth-parts usually concealed by prosternal chin piece; prosternal process fits into mesosternal cavity; metasternal transverse suture distinct; tarsi long and simple.

Larvae broadly oval, strongly flattened and disc-like, with head and legs concealed from above, and disc clothed with pattern of granules and modified setae, lined with marginal fringe of hairs, and provided with 2--4 pairs of defensive gin traps. Antennae long; labrum large; maxillae freely movable but partly concealed behind expanded postmentum. Functional spiracles on segment 8 in final instar only; spiracular brush on T9 opposite each spiracle prevents silt from clogging opening; S9 with movable operculum, concealing chamber which houses paired retractile anal gills.

Distribution

The family is represented in Australia by Sclerocyphon , which is most closely related to the Chilean Tychepsephus . These genera belong to the widespread subfamily Eubriinae.

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