Drosophila lanaiensis Grimshaw, 1901

Magnacca, Karl N. & Price, Donald K., 2012, New species of Hawaiian picture wing Drosophila (Diptera: Drosophilidae), with a key to species, Zootaxa 3188, pp. 1-30 : 15-17

Drosophila lanaiensis Grimshaw, 1901

Fig. 3

Drosophila lanaiensis Grimshaw, 1901:60 . Type Ƥ, Lāna‘i, 2,000 ft., xii.1893, R.C.L. Perkins, BMNH. Drosophila virgulata Hardy and Kaneshiro, 1968:234 – 236 n. syn. Holotype 3, Maui, Waikamoi, 22.ix.1966, J. P. Murphy. BPBM 8921.

Diagnosis. The wing and body coloration patterns resemble others in this species complex, including D. digressa of Hawai‘i, to which it is closest, and D. moli of O‘ahu. It is externally almost identical to the former except in the usually darker coloration of the anterior wing mark and median mesonotal stripe; the latter is distinguishable by the pointed wings and more extensive front leg setation of the male, and L-shaped mark on the dm-cu crossvein in both sexes (compare Figs. 3 and 4 ). See Discussion below.

Description. Male. Head. Front pale, faintly tinged with brown; ocellar triangle black. Fronto-orbital setae normal, anterior reclinate very small, about half as long as the proclinate and one-third as long as the posterior reclinate. Face and gena pale yellow except for a small black spot below the eye. Antenna with the second segment brown, third segment dirty yellow; arista with about 6–8 dorsal and 3 ventral rays in addition to the apical fork, and several rather long median branches. One strong oral vibrissa, followed posteriorly by several smaller setae, with numerous small setulae in between them. Palp largely yellow, slightly darker at the tip, nearly cylindrical; with a long, thin, yellow-brown apical seta. Thorax. Mesonotum largely yellow with three strongly contrasting dark brown to black stripes; lateral stripes dark, extending from the anterior margin of the humeri nearly to the scutellum; median stripe often fainter, broadening between the dorsocentral setae to fill the space between them, and extending onto the scutellum. Pleura almost entirely yellow except for a large dark mark on the posterior half of the anepisternum. Two pairs of strong dorsocentral setae, the anterior about 2/3 as long as the posterior. Legs. Entirely yellow, with faint tinges of brown at apices of femora and both ends of hind tibiae. Front tibia with anterodorsal and posterodorsal rows of 6–8 long cilia each along its entire length, slightly longer and more tightly clustered at the base; spacing irregular, often with large gaps. Front basitarsus with 7–11 dorsal cilia arranged in one or two irregular rows, similar to those of the tibia. Second and third tarsal segments also with 2–3 cilia. Wings. Shape normal, about three times as long as wide, rounded or only weakly pointed at apex. Subbasal wing spot small, scarcely reaching into cell R2. Anterior mark elongate, extending along about 1/3 the length of the wing; connected to the hourglass-shaped mark on the dm-cu crossvein via a small circular mark over R2+3. Apical marks confluent or nearly so. Costal fringe extending about 1/2 the distance between apex of R2+3 and R4+5. Abdomen. Coloration variable, from each segment predominantly yellow with only a narrow posterior band dark brown, to predominantly brown with yellow anterolateral areas. Cerci yellow-brown. Parameres of aedegus each with a very short apical setula.

Female. Identical to the male with the following exceptions. Head. Third antennal segment brown. Apical seta of palp shorter, stronger, black. Thorax. Median stripe of mesonotum broader on the anterior half and dark, similar to the lateral stripes. Legs. Front legs without elongate cilia or setae. Abdomen. Ovipositor long, straight, brown, pointed vertically at rest.

Material examined. L ā na‘i: 2 syntype Ƥ, Lāna‘i, 2,000 ft., xii.1893, R.C.L. Perkins ( BMNH and BPBM). 13, ravine by Hi‘i well, 20° 48.837'N 156° 52.772'W, A. & M. Hoikkala and S.L. Montgomery. Identified as D. virgulata: Maui : Holotype 3 and allotype Ƥ, Waikamoi, 22.ix.1966, J.P. Murphy, J31C1. 13, ‘Īao Valley, 20° 53.115'N 156° 32.637'W, 10.iii.2010, S.L. Montgomery. 1Ƥ, Makawao Forest Reserve nr. reservoir, 2900 ft., 20.829°N 156.272°W, 11.iii.2010, D. Kapan. 23 3Ƥ, Waikapū Valley, 15.x.2011, KNM.

Distribution and ecology. Maui and Lāna‘i; probably occurs on Moloka‘i or formerly did. Breeds in Charpentiera (pāpala, Amaranthaceae ).

Discussion. The recent collection of a male of this species from Lāna‘i has finally allowed proper assignment of this name. The original description mentions a series of five females, but only one is present at the Natural History Museum (London). It is missing its head but otherwise in reasonably good condition. Another is at the Bishop Museum and is in good condition; I have examined both of these, the latter in person and the former in photographs, and they are identical. Hardy (1965) considered D. lanaiensis conspecific with specimens from O‘ahu (described below as a new species, D. moli ). Examination of the wing pattern shows that it instead matches D. virgulata , described from Maui; most obviously, the mark over the dm-cu crossvein is hourglass-shaped instead of Lshaped as in D. moli . The recent male specimen also matches D. virgulata in wing pattern, wing shape, and front leg setation. Therefore, Drosophila virgulata Hardy and Kaneshiro is reduced to a new junior synonym of Drosophila lanaiensis Grimshaw. While there are distinct differences in the wings and legs between the present species and D. moli , it is nearly identical to D. digressa of Hawai‘i—in fact, the only consistent character separating them is the much longer seta of the aedeagal paramere (see Fig. 5 in Kaneshiro, 1969) of D. digressa . The latter typically has the anterior wing mark and median mesonotal stripe paler, but these are not consistent and dark individuals look externally almost identical to typical D. lanaiensis . However, they exhibit a high degree of mitochondrial gene sequence divergence— D. lanaiensis is 5.9% (Lāna‘i) to 6.5% (Maui) different from D. digressa in the 5' cytochrome oxidase I (COI) region, while D. lanaiensis from Lāna‘i and Maui differ from each other by only 0.7% (unpubl. data)—indicating a long history of separation between Maui Nui and Hawai‘i populations, and exchange or recent vicariance between Maui and Lāna‘i. Thus, they are maintained as two species.

Figures

FIGURE 3. Drosophila lanaiensis. A. Right front leg of Lāna‘i male, anterior view. B. Male wing. C. Wing of type female (Lāna‘i) in BMNH. D. Wing of recent female from ‘ Īao Valley, Maui.

FIGURE 4. Drosophila moli. A. Right front leg of male, anterior view. B. Male wing. C. Female wing.

FIGURE 5. Drosophila nukea. A. Right front leg of male, anterior view. B. Wing.