Overview

Recent studies indicate that the previously accepted families Tethinidae and Canacidae should be treated as a single family. Commonly called Beach flies or Surge flies.

Most species are restricted to the seashore (few exceptions), but one unnamed species is recorded from Lake Eyre. Habitats include beaches, estuarine tidal flats, mangrove, and wave-swept rocks. Larvae may be mainly algal feeders in the intertidal zone, but are little known. Larvae of Apetaenus utilise penguin dung as well as kelp. Adults of T hitena cadaverina Munari were found on a dead shore-bird.

Description

Canacids are generally small, dull grey to brown flies with the following diagnostic features:

Incurved lower orbital bristles absent; vibrissa often distinct; anepisternum bristled; vein C with break at subcostal position, no break at humeral position; vein Sc reduced, not ending independently in vein C; cell bm closed (except in Peolmyia ); cell cup closed (except in Zalea ); vein A1CuA2 vestigial or scarcely sclerotised; vein A2 generally visible as a trace or crease.

Apetaenus watsoni Hardy of Macquarie Island has vestigial wings.

Distribution

The family is almost worldwide. Of the six subfamilies, Apetaeninae, Canacinae, Pelomyiinae, Tethininae and Zaleinae occur in the Australian fauna, represented by a total of 42 described species. The Apetaeninae are absent from mainland Australia, but are represented on Macquarie Island by the vestigial-winged Apetaenus watsoni Hardy.