Subfamily Donaciinae Kirby, 1837

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Subfamily Donaciinae Kirby, 1837

Donaciinae Kirby, W. 1837. Part fourth and last. The Insects. xxxix + 325 + [2] pp., 8 pls. in Richardson, J. (ed.). Fauna Boreali-Americana; or the Zoology of the Northern parts of British America: containing descriptions of the objects of natural history collected on the late northern land expeditions, under command of Captain Sir John Franklin, R.N. London : J. Murray. [222].

Introduction

The subfamily Donaciinae is small, with eight genera and approximately 160 species worldwide, primarily in the Northern Hemisphere (Borowiec 1984; Askevold 1990). The single Australian species is confined to permanent water systems in the tropics (Reid 1993).

The Donaciinae are monophyletic (Askevold 1990) and belong in the sagrine group of subfamilies, with Sagrinae, Bruchinae and Criocerinae (Schmitt 1989; Askevold 1990; Reid 1995, 2000; Gomez-Zuita et al. 2008). The genus Donacia is also monophyletic (Askevold 1990) and divided into several subgenera of doubtful systematic status (Sota & Hayashi 2004). However, the single Australian species, Donacia australis Blackburn, is clearly a member of subgenus Cyphogaster, defined by presence of a pair of tubercles on the male first ventrite and widespread in east and South-East Asia (Reid 1993).

Adults of Donaciinae are at least semi-aquatic and the known larvae are truly aquatic. Both adults and larvae show specialisations for aquatic life: adults with a ventral plastron (air-collecting mat of hairs), larvae with only last pair of spiracles functional, modified into syringes for tapping into the air-carrying xylem of the host. The larva is therefore able to remain permanently submerged (Houlihan 1969). The species of subgenus Cyphogaster, including D. (C.) australis, feed on waterlilies, primarily Nymphaeaceae (Reid 1993; Sota & Hayashi 2004). The larva of Donacia australis has been described: it has a hooked epipharynx for extra anchorage (Reid 1993). Pupation is in an underwater cocoon, attached to the host. Adults mate and feed on emergent vegetation, are active fliers and are attracted to light.

Diagnosis

Adult: eyes with simple, unexcavate, inner margin; ventral plastron present (dense mat of silvery or golden setae); femora not ventrally toothed; legs elongate, hind tibia about one third body length; wings with only one anal cell; tegmen with dorsal cap.
Larva: aquatic; white, without dark dorsal sclerites; first instar without eggbursters; galea and lacinia spine-like; abdominal segment 8 with dorsal spiracles modified into two sharp-tipped siphons.