Barretthydrus geminatus Lea, 1927

Alarie, Yves, Michat, Mariano C., Hendrich, Lars & Watts, Chris H. S., 2018, Larval Description and Phylogenetic Placement of the Australian Endemic Genus Barretthydrus Lea, 1927 (Coleoptera: Dytiscidae: Hydroporinae: Hydroporini: Sternopriscina), The Coleopterists Bulletin 72 (4), pp. 639-661 : 646-647

Barretthydrus geminatus Lea, 1927 ( Fig. 15 )

Source of Material. Larvae were collected in association with adults at the following locality: Australia, New South Wales, 13 km NNW Dungog, Williams River, Tillegra Bridge , 109 m., 19. X.2006, 32.19.078S 151.41.250 E, L. Hendrich leg. (NSW 84).

Diagnostic Combination (Instar III). The third instar of B. geminatus can easily be distinguished from that of the closely similar B. tibialis by the absence of maculae on the dorsal surface of the head capsule ( Fig. 15 ), in addition to a relatively longer head capsule compared to the length of abdominal segment VIII (HL/LAS>4.60 compared to <4.50) and a lower total number of secondary setae on selected leg articles ( Table 3 ).

Instar I No specimen available for study.

Instar II No specimen available for study.

Instar III ( Fig. 15 )

Description. Color: Head capsule testaceous ( Fig. 15 ); head appendages pale yellow; thoracic tergites dark brown; abdominal tergites I – III brown mesally, broadly yellow laterally, IV – VII dark brown, VIII pale yellow; urogomphi dark yellow; legs predominantly dark yellow except coxae brownish. Body: Measurements and ratios that characterize the body shape in Table 1 . Head: Head capsule as in Fig. 15 , HL = 1.27–1.36, HL/LAS>4.60. Abdomen: U1 = 1.29–1.45 mm, U1/HW = 1.37–1.49. Chaetotaxy: ProFE with less than 45 secondary setae; mesoFE with less than 51 secondary setae; mesoTI with less than 45 secondary setae; mesoTA with less than 30 secondary setae; metaCO with less than 18 secondary setae; metaFE with less than 53 secondary setae; metaTI with less than 46secondary setae; metaTA with less than 38 secondary setae.

Figures

Figs. 15–16. Barretthydrus species, instar III, dorsal surface of head capsule. 15) B. geminatus; 16) B. tibialis. Scale bars = 0.10 mm.