Hermatobates djiboutensis Coutière & Martin, 1901

Anderson, R. Charles, Adam, M. Shiham & Cheng, Lanna, 2023, Marine insects of the Maldives (Heteroptera: Gerridae, Hermatobatidae and Veliidae; Diptera: Chironomidae) with notes on taxonomy, Indo-Pacific distribution, and ecology, Raffles Bulletin of Zoology 71, pp. 478-490 : 486

Hermatobates djiboutensis Coutière & Martin, 1901

Hermatobates djiboutensis is confined to the Red Sea and western Indian Ocean and is not found in Southeast Asia ( Polhemus & Polhemus, 2012). It is the only species of this genus found in the Maldives, where it was first collected by Phillips (1959) and was the most frequently collected marine insect in our samples ( Table 1). We collected it from inside the atolls, both in island and atoll lagoons, but not immediately adjacent to islands ( Tables 1, 2; Fig. 2D). We assume that this species’ habitat and behaviour do not differ from those of other Hermatobates species elsewhere: they live and hide in crevices of intertidal rocks or stone walls at high tide, coming out to feed only at low tide. If they are prevented from returning to air-filled cavities when the tide turns, they are able to skate freely over the sea surface for long periods of time. Specimens caught by us are presumably those that have strayed from their typical inshore habitats ( Cheng & Leis, 1980; Cheng & Schmidt, 1982). This species is known to be highly attracted to light at night and it is not uncommon to catch dozens of specimens using night lights (e.g., samples 30 and 37, Table 1). For this species, 84% of the specimens in our Maldives samples were taken at night using lights, the highest percentage for any of the species we collected. Adult males can be easily distinguished from adult females. In the male, the meso- and metanota are completely fused and extended posteriorly to cover part of the abdomen ( Fig. 6A ), and the genital segments are modified ventrally ( Fig. 6B ). In the female, some of the abdominal segments can be clearly seen between lateral lobes of the metanota ( Fig. 6D ), and the genital segments are not modified ( Fig. 6D ). Furthermore, the male front leg is highly modified, with small teeth and tooth-like tubercles along the inner margin of the tibia ( Fig. 6C ); these are presumably used for grasping the female during mating.

Figures

Fig. 6. Hermatobates djiboutensis. Specimens from Meerufenfushi Island, Kaafu (North Malé) Atoll, 14 November 2006. Scale bar = 0.5 mm. A, male, dorsal view; B, male ventral view (length ca. 3.8 mm); C, male front leg showing teeth and tubercles on tibia (length of femur ca. 0.8 mm); D, female, dorsal view (length ca. 3.6 mm); E, female, ventral view.