Drosophila sp.

Mcevey, Shane F. & Polak, Michal, 2021, Drosophilidae (Diptera) of the Cook Islands, Records of the Australian Museum (Rec. Aust. Mus.) 73 (5), pp. 153-170 : 158

Drosophila sp. aff. funebris

Figs 3–12

Drosophila funebris (Fabricius, 1787:345) , the type species of the genus Drosophila , and therefore of the family Drosophilidae , is rarely encountered in the Australian or Oceanian Regions. Listed from all major biogeographic regions of the world ( Brake & Bächli, 2008), it is rare in the Oriental ( Japan [ Okada, 1968]; Korea [Okada, 1974]) and Australian Regions (specimens collected in Sydney e.g., 1916, 1917, 1924, 1949 and 1978: K.118090–92, K.118083– 84, K.356399, K.118085–87, K.274079, K.471590–91, K.118089, no specimens collected in Sydney since 1978). It is apparently absent in New Guinea ( Carson & Okada 1983, and pers. obs.). It is common in the Palaearctic Region ( David & Tsacas, 1981) and in South Africa ( McEvey et al., 1988).

A number of New Zealand (Christchurch, Wellington, Auckland, Dunedin, Rangiora) records of Drosophila funebris exist (Harrison, 1952, 1959). Harrison recognized that the New Zealand names D. clarkii Hutton, 1901 and Leucophenga atkinsoni Miller, 1921 were, in fact, junior synonyms of D. funebris .

A single female specimen (AM K.471932) was taken during the present survey at “Rarotonga top end trail” ( Tables 2, 3). The specimen agrees in general morphology and cephalo-chaetotaxy ( Figs 3–6 ) with others from elsewhere in the world but the wings and oviscapt differ. Wing metrics of specimens from New Zealand, Australia, Spain and South Africa have been examined. While specimens from around the world conform with each other, the Cook Island specimen stands out—the wing measures are significantly different ( Table 4). For example: the C-index is about 2.0 in the Rarotonga fly, but 2.82–3.32 in specimens from South Africa, Spain, Australia and New Zealand; the fringe of heavy setation in the third costal section is almost entire in the Cook Islands fly but less than half in D. funebris from Australasia, Africa and Europe ( Figs 7–8 and C3F in Table 4); and the 4c-index is 1.26 in Rarotonga but 0.65–0.79 in D. funebris worldwide ( Table 4). There is also a remarkable difference in the size of the costal spine pair at the subcostal break ( Figs 9–10 ).

The terminalia of the single available specimen has been dissected. The spermathecae, unfortunately, were not recovered. The oviscapt ( Fig. 11 ) has a form quite unlike Drosophila funebris —there is no preapical bump on the dorsal margin (arrowed in Fig. 12 ), a distinguishing character for D. funebris . Furthermore, and also unlike D. funebris , there are 2–3 strong upward-pointing, subapical, peg ovisensilla ( Fig. 11 ) and no single, long, ventral, subterminal, trichoid ovisensilla (cf. D. funebris , Fig. 12 ).

The magnitude of these differences is such that there would, under other circumstances, be little doubt that the Cook Islands specimen represents a new, undescribed species. However, only one female is available for study and so it is noted as exceptional but not used here to describe a new species. Additional specimens, and males, from the Rarotonga (and Cook Islands) population would permit a more confident determination and a better understanding of its morphological deviation in the TSP .

Figures

Figures 3–10. Comparison of Drosophila sp. aff. funebris from Cook Islands (left) and D. funebris (right): (3, 4) lateral views of head; (5, 6) dorsal views of cephalo-chaetotaxy, back of head, and scutum anteriorly; (7, 8) ratio of heavy to light costal setation in third costal section of wing—almost entire in Cook Island specimen, only about 0.4 in D. funebris (see Table 4); and (9–10) costal spine size at subcostal break (second spine of pair broken off in Fig. 9 photo). All specimens in AM: Figs 3, 5, 7, 9—K.471932 (Rarotonga);Figs 4 (K.353509), 6 (K.353514),8 (K.353510),and 10(K.353614)(all D.funebrisfromJohannesburg).Scaleis 200 µm.

Figures 11–12. Dissimilar oviscapts of Cook Island species (left) and Drosophila funebris (right). (11) Drosophila sp. aff. funebris from Rarotonga, Cook Islands (Australian Museum, K.471932); (12) Drosophila funebris, with the unique preapical bump on the dorsal margin arrowed; AM K.353519 | Johannesburg | South Africa | vi.1985 | coll. S.F. McEvey | McE2956.