Megaselia mera (Collin)

Disney, R. Henry L., 2006, Nine new species of Megaselia Rondani (Diptera: Phoridae) from the Seychelles, Zootaxa 1210, pp. 1-25 : 14-16

Megaselia mera (Collin)

( Figs 20, 21 , 25–28 )

Aphiochaeta mera Collin, 1912 .

Megaselia mera (Collin) . Borgmeier, 1968.

As M. jorgensis Disney (1991) , from the Cape Verde Islands, and two species, described below closely resemble this species, which was omitted from Beyer’s (1965) keys, it is necessary to clarify its recognition first. In Beyer’s keys M. mera runs to couplet 3, lead 2, on page 56, to M. lilliput Beyer , which is only known from a single female from Angola. Likewise Collin described this species from a single female from the Seychelles. I have remounted his holotype female on a slide. This revealed an error in the original description when it stated that the frons is longer than wide. In fact it is slightly wider than the midline length. This means the species closely resembles the female of the subsequently described M. jorgensis . The latter has straw yellow, as opposed to yellowish brown postpedicels, and its abdominal tergite 7 lacks the small, incipient, anterolateral apodemes that are present in M. mera (cf. Figs 24 and 25 ). Other details of the female of M. mera are shown in Figs 21 and 26 . Internally it has only two rectal papillae and a simple Dufour’s crop mechanism that is rounded behind and about twice as long as its greatest breadth.

The females of these two species closely resemble the description of Beyer’s species, which differs only in having dark brown haltere knobs, darker brown postpedicels and in supposedly lacking the Sc, which is present but faint in M. mera and M. jorgensis , and the posterodorsal hairs of the mid tibia being differentiated in the lower half only, unlike M. mera and M. jorgensis .

The hitherto unknown male of M. mera is described below. It also proves to very similar to M. jorgensis . They are most readily distinguished by the labella of the proboscis, being broadened anteriorly ( Fig. 20 ) (as in the next species, Fig. 22 ) as opposed to being narrowed anteriorly in M. jorgensis ( Fig. 19 ). In addition the colour of the postpedicels of the two species differ as in the females. Relevant details of M. jorgensis are given in Figs 15–19 and 24 for comparison with M. mera .

Male

Frons brown, a little broader than long, with 80–104 hairs and dense but very fine microsetae. SAs robust but lower pair shorter and weaker. Upper SAs slightly lower on frons than antials which are about equidistant from anterolaterals, which are distinctly higher on frons. Pre­ocellars ranging from being closer together to a little further apart than either is from a mediolateral bristle, which is about level with the former. Cheek with 3–5 bristles and jowl with 1–2 longer ones. Postpedicels subglobose, straw yellow lightly tinged brown, and without SPS vesicles. Palps pale straw yellow, with 5 bristles (all clearly shorter than lower SAs) and 1–6 hairs. Labrum ( Fig. 20 ) almost as pale as palps and about 0.6x as wide as postpedicel. Labella ( Fig. 20 ) about as dark on top, and with dense fields of short spinules below. Thorax chestnut brown, being a little paler on sides. Mesopleuron bare. Two notopleural bristles and no cleft in front of these. Scutellum with an anterior pair of hairs (shorter than hairs at rear of scutum) and a posterior pair of bristles. Abdominal tergites brown with the hairs at rear of T6 longer than rest ( Fig. 27 ). Venter dusky straw yellow, and with hairs below segments 5–6, those on 3–4 being reduced to microsetae. Hypopygium brown, but anal tube pale straw yellow, and as Figs 27 and 28 . Right lobe of hypandrium vestigial. With two rectal papillae. Legs straw yellow apart from brown tip to hind femur and brown patch on mid coxa. Fore tarsus with posterodorsal hair palisade on segments 1–5, and 5 slightly longer than 4. Dorsal hair palisade of mid tibia extends about 0.8x length. Some of hairs below basal half of hind femur clearly longer than those of anteroventral row of outer half. Hind tibia with 8–10 clearly differentiated posterodorsal hairs. Spinules of apical combs simple. Wings 1.0– 1.2 mm long. Costal index 0.41–0.42. Vein 3 unforked. Costal ratios 1.3–1.6: 1. Costal cilia (of section 2) 0.05–0.06 mm long. A small hair at base of vein 3. With 1–2 (usually 2) axillary bristles, the outer being longer than costal cilia. Sc not reaching R1. Veins brown but 7 pale and obscure basally. Membrane lightly tinged grey. Haltere with yellowish brown knob that is typically paler than the stem.

Material

Holotype female, Seychelles (19 – NHM, BMNH (E) 249426). 4 males, 3 females, Silhouette Island, La Passe, 1– 4 July & 10–12 August 2000, J. Gerlach ( CUMZ, 8­98, 118, 125; 4 males, S. I, Jardin Marron, 2000–2001, J. Gerlach ( CUMZ, 8­133, 141, 142); 2 males, Grande Barbe, Old Village, 2 June 2001 J. Gerlach ( CUMZ, 8­137); 2 males, Lantana, Lantana North, 30 July­1 August 2000, J. Gerlach ( CUMZ, 8­1§26); 1 male, St Anne Is., 12 December 2001, J. Gerlach ( CUMZ, 8­145).

Figures

FIGURES 15 – Megaselia jorgensis. (15) male, left face of hypopygium; (16) female, vaginal sclerites; (17) female, abdominal tergites 2 – 6. Scale bars = 0.1 mm.

FIGURES 18 – 23. Megaselia species, labrum and labella of proboscis from above. (18) M. jorgensis female; (19) M. jorgensis male; (20) M. mera male; (21) M. mera female; (22) M.

FIGURES 24 – 28. Megaselia species, details of abdomen. (24) M. jorgensis female, tergite 7; (25 – 28) M. mera: (25) female, tergites 6 and 7; (26) female, vaginal sclerites (anterior end facing top of page); (27) male, left face of hypopygium; (28) anal tube from another angle. Scale bars = 0.1 mm.