Conopidae (D. McAlpine, 2002)

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 : 131-132

The Conopidae

Examples used in this study include Myopa sp. (subfamily Myopinae ), Australoconops unicinctus (Kröber) , and Heteroconops sp. (subfamily Conopinae ). Though these species show a range of variation, a wider range of observations will be necessary to make generalizations for the family.

In Myopa sp. segment 2 is moderately short and stout, narrowed basally and broadly funnel-like distally ( Fig. 42 ). The flange-like rim is continuous without division into dorsal lobes. The external surface is densely microtrichose and bears a number of stout setulae. In several observed examples the setulae on the medial surface are partly or extensively broken or abraded. The distal articular surface is broadly concave and bears numerous fine, simple microtrichia which are not grouped into combs nor located on ridges. The conus rises from the dorsomedial part of the articular surface. It is narrow basally and dilated and bilaterally compressed distally, apparently well sclerotized and rigid; the distal foramen is located subterminally on the outer lateral surface; it has a narrow foraminal ring; the annular ridge is only slightly prominent and bears a moderate number of small compact tubercles, some rounded, some bearing a minute microtrichium. The general surface of the conus is almost devoid of microtrichia, but bears many short, smooth transverse ridges.

Segment 3 is rather short, inflated, and without basal stem. The apparent sacculus is situated on the outer lateral surface, slightly ventrobasally of its centre, and is only slightly larger than numerous sensory pits on this surface, but it is differentiated by the possession of fine trichoid sensilla in the mouth region, as well as one larger ovoid-cylindrical sensillum arising from the floor of the cavity. The arista is shorter than segment 3, inserted slightly laterad of mid-dorsal position on segment 3, and is three-segmented.

In Australoconops segment 2 ( Fig. 43 ) is elongate, gradually expanding distally, with the distal articular surface oblique, concave ventrally and bearing the conus dorsally. The conus is elongate, irregularly subcylindrical, weakly sclerotized and apparently flexible. The distal foramen is exceptionally large, subcircular, without a marked annular ridge, and terminal on the conus. The button was not located, probably because of the irregular surface of the conus. Segment 3 ( Fig. 44 ) is somewhat elongate, bulbous basally and tapered distally. There is a large basal hollow into which the conus is inserted. The apparent sacculus opens on to the lateral surface near the base of the segment. There is a relatively large opening facing basally on the basal swelling of segment 3, which leads into a cavity much larger than that of the sacculus. This cavity ( Fig. 44 , pp), which I term the postpedicellar pouch, in analogy with that of the orthogenyan genus Hormopeza , has a thick transparent wall with a pigmented lining. Its mouth, though microtrichose, lacks the scabrous surface of the sub-basal caecum of some families, and is unlikely to be homologous with that structure. The microstructure of the pouch is not visible in my preparations, and it is not evident whether its function is sensory or glandular. Under CLM the sacculus appears to be superimposed on the pouch (in lateral view), but it is not clear if there is any connection between their walls.

The postpedicellar pouch is present in both sexes of Australoconops unicinctus . It is also present in Heteroconops sp. and probably at least some other taxa of Conopinae . Its opening is usually concealed in whole specimens, as it is on the surface which faces into the concavity of the distal articular surface of segment 2, but it is readily visible in cleared antennae under CLM. The condition in Physocephala texana (Williston) appears to be more complex but has not been examined in detail. The conus of Heteroconops is similar to that of Australoconops but is more elongate. The remarkable resemblance in structure of segment 2 between certain taxa of Conopidae and Pyrgotidae is mentioned under the latter family. I have previously noted variation in the number of aristal segments in the Conopidae (D. McAlpine, 2002) .

Various studies of the Conopidae have failed to demonstrate convincingly its nearest relatives among the schizophoran families. The peculiarities of the conus and postpedicellar pouch appear to be apomorphies restricted to the subfamily Conopinae , and are therefore not relevant to the broader problem of relationships.

During this rapid selective check of conopid morphology, I have noticed major differences in the subscutellum (sensu J. McAlpine, 1981) between taxa. In Stylogaster spp. the subscutellum is large, deep, and medially extended so as almost to divide the postscutellum; in other conopid taxa examined the subscutellum is quite narrowly transverse or vestigial above the large postscutellum. This variation may have taxonomic significance.

Figures

Figures 42–44. Antennae of Conopidae. (42) Myopa sp., right antennal seg. 2. (43) Australoconops unicinctus (Kröber), part of right antennal seg.2. (44) The same, right antennal seg.3. bh, basal hollow; bu, pedicellar button; c, conus; da, distal articular surface; m, mouth of postpedicellar pouch; pp, postpedicellar pouch; sc, sacculus (seen superimposed on postpedicellar pouch).