Hydrobiosella letti group

Diagnosis. Key characters of males in the group are parameres elongate and straight or slightly curved, arising near base or middle of phallus, and preanal appendages absent.

Description. Head and body generally brown; wings light brown to brown. Medium sized adults. Forewing length, males: 4.5-8.0 mm; females: 5.8-9.4 mm; forewing length about 2.9-3.0 times maximum width, wing venation (Fig. 17), similar to H. stenocerca (Mosely and Kimmins 1953, fig 265a), H. bispina (Cartwright, 2010, fig. 1) and H. waddama (Mosely and Kimmins 1953, fig. 269a), R1 simple, forks 1, 2, 3, 4 and 5 present; forks 1 and 2 sessile; fork 2 with nygma, about 1.3-1.4 times length fork 1; fork 3 shorter, length about two-thirds length fork 2, fork 3 length ranging from between 1.6-1.7 times length footstalk, cross-veins r-m and m contiguous at fork 3; fork 4 similar length to fork 3, fork length about 2.0-2.2 times length footstalk; fork 5 very long, length between 1.9-2.0 times length fork 4; discoidal cell closed, length between 3.7-3.9 times maximum width. Hind wing length about 2.6-2.7 times maximum width, with forks 1, 2, 3 and 5 present; forks 1 and 2 sessile; fork 2 with nygma present, fork 2 length between 1.6-1.7 times length fork 1; fork 3 shorter, length about two-thirds length fork 2, fork 3 longer than footstalk, length fork ranging between 1.9-2.1 times length footstalk; fork 5 very long, length between 1.6-1.7 times length fork 3; discoidal cell closed, length between 4.1-4.3 times maximum width; with three longer anal veins (Fig. 17).

Male. Segment IX in lateral view, length between 1.2-1.9 times width, usually sub-rectangular (Figs 19, 37), occasionally projecting and tapered basally (Fig. 25) with a shallow, wide V notch (Figs 29, 32) or wide, shallow concavity medially on distal margin (Figs 23, 26). Segment X mainly sclerotised dorsally, membranous ventrally, usually broadbased, tapered distally; in dorsal view, with a ‘tongue-shaped’ process (Figs 18, 21, 24). Phallus generally tube-like, parameres slender, elongate and straight or slightly curved, arising near base of phallus (Figs 19, 22, 28). Inferior appendages with two segments, in lateral view, basal segment usually more robust than harpago. Harpago has a small field of dark spines meso-distally (Figs 19, 22, 31).

Female Genitalia typical of genus (Figs 42, 43).

Larva. No confirmed larvae are known for this group.

Remarks. The seven species in this group are known from NE-Victoria, eastern New South Wales and eastern Queensland. Females of only two species have been associated.

Key to males of species of the Hydrobiosella letti group from Australia

1. Segment X with pair of baso-lateral lobes (Figs 18, 19); SE-Qld H. fibra

- Segment X without pair of baso-lateral lobes (Figs 21, 22, 24, 25) 2

2. Segment X in dorsal view, with pair of small apico-lateral projections (Fig. 22); NE-Qld H. bifurca

- Segment X in dorsal view, without pair of small apico-lateral projections (Figs 25, 28) 3

3. Segment X laterally compressed apically, with distinctive notch (Figs 24, 25); SE-Qld H. incisura

- Segment X not laterally compressed apically, without distinctive notch (figs 27, 28) 4

4. Inferior appendages in lateral view with harpago length> 3.5 times width (Figs 28, 31) 5

- Inferior appendages in lateral view with harpago length <2.5 times width (Figs 34, 37) 6

5. Segment X in lateral view, slightly dilated apically (Fig. 28); in dorsal view, slender; length about 2.8 times maximum width (Fig. 27); NE-Qld H. tenuitas

- Segment X in lateral view, not dilated apically, instead slender and upturned (Fig. 31); in dorsal view, not slender; length about 1.4 times maximum width (Fig. 30); NE-Qld H. exilatis

6. Inferior appendages with basal segment angled dorso-mesally (Fig. 34); NE-Vic H. bos

- Inferior appendages with basal segment not angled dorso-mesally (Fig. 37); CE-NSW H. letti