Drosophila pilipa Magnacca

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 : 25-26

Drosophila pilipa Magnacca , new species

Fig. 9

Diagnosis. This unique species cannot be mistaken for any other. Although the wing pattern and body markings superficially resemble D. hemipeza and D. substenoptera of O‘ahu, the elongate, pointed wings of the male (lacking an extra crossvein) and frontal setae (modified in both sexes, but elongate and conspicuous in the male) distinguish it immediately.

Description. Male. Head. Front yellow, with a narrow brown stripe extending through the ocellar triangle to the frontal suture. Orbits lacking the usual proclinate and reclinate setae, instead with about 18–20 long, erect setae on each side in 3 irregular rows; these are about as long as the ocellar setae (slightly shorter posteriorly) and straight for most of their length, the apical 1/5 abruptly bent back. Orbits nearly reaching the frontal suture but only slightly broadened; median frontal area almost bare, with only a few small proclinate setulae near the frontal suture. Face yellow, gena broadly brown immediately below the eye. Antenna with the second segment brown, third segment yellow; arista with about 8 dorsal and 4 ventral rays in addition to the apical fork, and 6 rather long median branches. One moderately strong oral vibrissa present, other oral setulae weaker, about half as long. Clypeus expanded, about as long dorsoventrally as the width of the palps; brown laterally, pale anteriorly. Palp brown, broad, and short, not extending beyond the clypeus, broadest just before middle; one subapical seta slightly longer than the others. Labellum tinged with brown. Thorax. Predominantly yellow. Mesonotum on each side with a narrow stripe just inside of the dorsocentral setae, and a broader stripe just outside of the setae, extending the full length. Anepisternum with a dark brown stripe along the dorsal margin; anepimeron with a large brown spot posteroventrally; katepisternum tinged with brown above the posterior seta. Metanotum with two broad brown stripes, in line with the mesonotal stripes. Two pairs of strong dorsocentral setae, the anterior about 2/3 as long as the posterior. Legs. All yellow except the apex of the hind tibia and fifth tarsal segments tinged with brown. Front legs lacking elongate cilia or other modifications. Wings. Long and narrow, about 3.5 times as long as wide. Brown markings present at the apex of R1, extending posterior to M; around the r-m and dm-cu crossveins; in an elongate mark on the mid anterior margin, occupying about 1/3 the wing length; and broadly at the apices of R2+3 and R4+5. Otherwise more or less evenly fumose, the background color distinctly yellow in cell C and in cell R3 between the basal spot and the r-m crossvein. The r-m crossvein is well beyond the end of vein R1; penultimate and antepenultimate segments of M equal, about half as long as the last segment. Posterior wing margin between M and CuA1 straight or slightly concave. Dm-cu crossvein nearly perpendicular to long axis of wing. Costal fringe extending about half the distance between apex of R2+3 and R4+5. Abdomen. Predominantly yellow, with a brown stripe extending along the lateral margins of all tergites and a medial brown stripe. Cerci semicircular, higher than long. Genitalia not dissected.

Female. Identical to the male with the following exceptions. Head. Erect setae of orbits short and straight, only slightly longer than the prostrate setulae of the median frons. Proclinate and posterior reclinate setae present but both directed laterally; normally sized, the latter about twice as long as the former. Wings. Not as long and narrow, about three times as long as wide. Posterior wing margin between M and CuA1 convex. Segments of M in approximately the same proportions as in the male, but dm-cu crossvein distinctly angled basad anteriorly, and the mark over it obliquely angled relative to the vein. Abdomen. Ovipositor long and narrow, held vertically at rest. Eggs with four very short filaments, less than 1/3 as long as the egg.

Types. Kaua‘i: Holotype 3, F1 offspring of allotype Ƥ coll. 24.vii.2010, 22.111°N 159.596°W, emerged 8.ix.2010 (UHIM). Allotype Ƥ, Alaka‘i Wilderness Preserve, Mōhihi Trail, 3800 ft., 22.111°N 159.596°W, on bait sponge, 24.vii.2010, K. Magnacca (UHIM); paratypes: 13 2Ƥ, same data as holotype, emerged 18–23.ix.2010 (UHIM). 2Ƥ (BPBM), 1Ƥ (UHIM), same data as allotype.

Other material. Kaua‘i: 13, Ku‘ia Natural Area Reserve, Mahanaloa Valley exclosure, 2200 ft., 22.135°N 159.700°W, on bait sponge, 23.vi.2009, K. Magnacca.

Distribution and ecology. Kaua‘i, mesic forest. Probably breeds in Charpentiera elliptica (pāpala, Amaranthaceae ). There are no records of rearing from field-collected material, but two wild-caught females presented with a variety of host extracts ( Charpentiera , Cheirodendron , Clermontia , Pisonia , Pleomele , and Wikstroemia ) laid eggs only on Charpentiera . This was also the only potential host shared between the two collection sites, though it was extremely rare at both.

Etymology. From the Hawaiian pilip ā, hedge or fence, referring to the dense frontal setae.

Discussion. This striking species appears to be a morphological link between the basal planitibia group species, D. hemipeza and D. substenoptera , and other species that lack an extra crossvein in the wing. It closely resembles both of those species in the coloration pattern of the wing, thorax, and abdomen. However, phylogenetically it groups with D. picticornis and D. setosifrons as sister to the nudidrosophila group based on nuclear gene sequences (Magnacca and Price, in prep.). The frontal setae of D. pilipa are somewhat reminiscent of D. setosifrons , albeit much longer. That these three species form a monophyletic group but are genetically and morphologically distant, and have very different hosts (sap fluxes, araliad bark, and Charpentiera bark), suggests they may represent relictual members of a formerly larger lineage that has been displaced by the grimshawi group.

Eggs laid in laboratory vials were deposited on the surface of paper tissues soaked with extract, rather than inserted into the tissue as with most other species. Few eggs were laid, about 2–7 per week for the two females, suggesting a low reproductive rate. The filaments are much shorter than any of the species examined by Kambysellis and Heed (1971), which included D. picticornis . Only a few eggs were observed; oviposition vials were changed every week and usually well-developed larvae were already present, indicating a very short period as an egg. The larvae developed on standard Wheeler-Clayton medium with no apparent mortality, but adult survivorship was low, apparently due to refusal to feed on the medium. Consequently the lab-reared adults did not survive to sexual maturity. Development was faster than in other species—total time from egg to adult was 33–35 days, with approximately 15 of those spent as a pupa.

Figures

FIGURE 9. Drosophila pilipa. A. Male head, lateral view (ptilinum protruding slightly). B. Male head, dorsal view. C. Female head, lateral view. D. Male wing. E. Female wing, posteroapical portion. F. Egg.