Scaptodrosophila marjoryae (Harrison, 1954)

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 : 168

Scaptodrosophila marjoryae

(Harrison, 1954:105)

Seventeen species of Scaptodrosophila are known from the Tropical South Pacific (TSP). During the present survey a pale brown Scaptodrosophila species with translucent or weakly pigmented setae and without thoracic vittae was collected on Aitutaki and Rarotonga. It has apical and basal scutellar setae subequal in length and is therefore not S. bryani or S. anuda (see above); it has C-index 2.11–2.23 (AM K.472185–88) and is therefore not S. scaptomyzoidea (Duda, 1923) — S. scaptomyzoidea has exceptionally high C-index in the range 4.0–4.7 ( McEvey & Dizon, 2017). This is not a black species or a species with blackened thorax or blackened tergites, nor is it a species with any form of thoracic banding or thoracic vittae. This effectively eliminates 12 of the remaining 14 described TSP Scaptodrosophila species. The present species appears to be very close to S. marjoryae (Harrison, 1954) previously reported only from Samoa ( Table 1, Fig. 1 , 1500 km distant). Scaptodrosophila marjoryae closely resembles S. concolor (Bock, 1976) and S. aurochaeta (Bock, 1984) from Australia.

Specimens with very similar morphology, and awaiting determination in the AM, have been examined by us from Vanuatu (AM K.380057), Moorea (McE10215 CNRS/ MNHN) ( Table 1, Fig. 1 ) and Townsville, Australia (Schiffer’s iso-female culture CBN17, AM K.357126–45 etc.). Unfortunately we have been unable to examine S. marjoryae from Samoa but our conclusion after a comparative study of male terminalia of these similar pale brown species with translucent setae from across the TSP and northern Australia is that at least four species exist; differences exist in specimens from Rarotonga, Port Vila, Moorea, and Townsville. Only three names are available (in the TSP and northern Australia), so types of S. marjoryae , S. concolor and S. aurochaeta must be examined before identifications can be made with confidence. In the interim, since we find no departure from Harrison’s description, we have determined the present species from the Cook Islands to be S. marjoryae and we leave open the question of possible synonymies with Australian species until further study.

Figures

Figure 1. Main islands or archipelagos of the Tropical South Pacific (TSP, above).The Cook Islands, as a country, includes Pukapuka coral atoll in the northern group; the present survey is restricted to the three large islands—Rarotonga, Aitutaki and Mangaia—of the Cook Islands southern group, boxed in blue above and enlarged below. Atolls and smaller islands in the Cook Islands southern group are named in grey below (see also Fig. 2 and Tables 1–3).