Lonchopteridae

McAlpine, David, 2011, Observations on Antennal Morphology in Diptera, with Particular Reference to the Articular Surfaces between Segments 2 and 3 in the Cyclorrhapha, Records of the Australian Museum 63 (2), pp. 113-166 : 127

The Lonchopteridae

In Lonchoptera bifurcata (Fallén) ( L. furcata auct.), which may be taken as morphologically typical of extant taxa of Lonchopteridae , segment 2 shows an apparent combination of plesiomorphic and derived conditions ( Figs 29, 30 ). The approximate radial symmetry of the segment resembles the plesiomorphic one for the Cyclorrhapha. However, the strongly developed angular rim surrounding the partly concave distal articular surface, and the presence of a well developed, elongate conus arising from the centre of this surface suggest the possibility of apomorphies shared with more advanced cyclorrhaphans, but some features of the conus indicate that this may not be so. The conus in the Phoridae and Ironomyiidae bears the button on its distal surface, and this is the usual and perhaps the primitive position for the button in the Eumuscomorpha. However, in Lonchoptera the button is situated at the extreme base of the conus where it adjoins the distal articular surface. I therefore point out the possibility that the lonchopterid conus is an independently derived structure resulting from the simple protrusion of the annular ridge and its associated foramen, in a primitively platypezid-like taxon, into the base of segment 3, without affecting the position of the button. This hypothesis allows for the independent evolution of the conus at least twice in the Cyclorrhapha, but this may not be surprising in view of the fact that a centrally inserted conus has also developed in the orthogenyan genus Dolichopus (Sinclair & Cumming 2006) , and such concealed structure may well have been overlooked in other non-cyclorrhaphous taxa.

Lonchoptera also differs from the Phoridae in retaining a relatively massive main body of segment 2 with a well developed encircling series of setulae, whereas extant phorid taxa have the segment reduced as explained below. A generally overlooked feature of at least some Lonchoptera spp. is the presence of a pair of secondary claw-like structures on the terminal surface of tarsal segment 5. These are concealed by the true claws so that detailed study is difficult (author’s observations with SEM).

The Cretaceous genus Lonchopteromorpha (see Grimaldi & Cumming, 1999), though described under “family Lonchopteridae (?)”, clearly has a bilaterally subsymmetrical (rather than radially subsymmetrical) antennal type, and possibly separate abdominal tergites 1 and 2 (op. cit. fig. 54); it therefore is probably not closely related to the Lonchopteridae . Lonchopteromorpha also differs from Lonchoptera in its short, strongly incrassate hind basitarsus.

Figures

Figures 29, 30. Lonchoptera bifurcata Fallén (fam. Lonchopteridae). (29) Left seg. 2, distal view. (30) Conus, lateral view. ar, annular ridge; bu, pedicellar button; c, conus; da, distal articular surface; r, rim.