Melaloncha, Brues, 1904

Brown, Brian V., 2004, Revision of the subgenus Udamochiras of Melaloncha beekilling flies (Diptera: Phoridae: Metopininae), Zoological Journal of the Linnean Society 140 (1), pp. 1-42 : 3-5

MELALONCHA

The terminal segments of female Melaloncha are highly modified for their parasitic way of life. Unlike Phalacrotophora and Melittophora , which retain a membranous segment 7 with a distinct dorsal tergite, segment 7 in Melaloncha is completely sclerotized, forming an ovipositor of various forms ( Figs 8, 9 ). In many species the ventral apex of the ovipositor is deeply cleft, allowing the posterior segments to be extended ventrally.

The section of the abdomen apparently corresponding to intersegment 7–8 in most other phorids is modified in all examined species of Melaloncha , with at least a dorsal, longitudinal, thin sclerite present. In other species the dorsal sclerite is modified with the apex forming a posterior point, usually sheathed in a clear, membranous structure or other lateral processes of unknown function ( Figs 10–12 ). In some species, this sheath has been modified to form a dorsal, threepronged structure ( Figs 8, 9 ) articulating with the sclerite; in some, the intersegment is relatively heavily sclerotized and brown in colour, proximal to the ovipositor. In some species related to M. obscurella Borgmeier there are rows of sclerotized hooks present

2 3 ventral u-shaped lobe sclerite u-shaped ventral lobe sclerite furrow basally on the intersegment. The function of all these modifications of the intersegment is probably to help guide the stylet to the proper location for egg deposition, or to give structural support to the posterior portions of the abdomen.

An argument could be made that the elaborate structures anterior to the stylet are actually part of segment 8, with the stylet formed by segments 9–10. I do not support this idea, however, because the stylet forms an identifiable, sclerotized capsule that is readily comparable with the same sclerotized structure in Phalacrotophora . In both Phalacrotophora and Melaloncha , the ventromedial cleft of segment 8 is a clearly visible landmark in this capsule ( Figs 5 , 13 ).

Posterior to intersegment 7–8 is the stylet, a term proposed by Brown (1993b) for the same structure in species of Apocephalus Coquillett. The stylet consists of the fused elements of segments 8–10 and forms an apically pointed structure for piercing the bodies of hosts, allowing eggs to be deposited therein ( Figs 13, 14 ). Cerci are absent. The stylet is nearly always withdrawn into the preceding body segments (usually within intersegment 7–8) in preserved specimens, resulting in the appearance that the sclerotized por-

13 14

tions of the intersegment, which frequently protrude from the ovipositor in preserved specimens, are the actual terminal portion of the abdomen. The dorsal apex of the stylet is sharply pointed and heavily sclerotized, whereas in Melaloncha the ventral apex is shorter or longer, and extremely reduced. Often, the ventral lobes appear as merely a pair of long, weakly sclerotized rods, that have thin, almost invisible (with stereoscopes) membrane between them ( Fig. 13 ). Apparently, the dorsal apex assumes the major role in piercing the host, whereas the ventral apex merely helps guide the egg out of the body.

Figures

Figures 8–14. Melaloncha species. Figs 8 & 9: Melaloncha (M.) sp. 22. 8. Posterior segments of ovipositor, dorsal. 9. Same, left lateral. Figs 10–12: Intersegment 7–8, dorsal. 10. M. simillima Borgmeier. 11. M. deinocerca Borgmeier. 12. M. trua sp. nov. Figs 13 & 14: Stylet, M. trua sp. nov. 13, ventral. 14, left lateral.

Figures 1–7. Phalacrotophora species. Figs 1–3: P. berolinensis Schmitz. 1. Posterior segments of ovipositor, dorsal. 2. Segments 8–10, dorsal. 3. Segments 8–10, ventral. Figs 4 & 5: Phalacrotophora sp., Ecuador, Napo R. 4. Segments 8–10, dorsal. 5. Segments 8–10, ventral. Figs 6 & 7: Anepisternum, left lateral. 6. P. fasciata (Fallén). 7. P. rufiventris Borgmeier.