Curtonotum quinquevittatum, Curran, 1933

Pollock, J. N., 2002, Observations on the biology and anatomy of Curtonotidae (Diptera: Schizophora), Journal of Natural History 36 (14), pp. 1725-1745 : 1734-1736

Curtonotum quinquevittatum anatomy

Since the anatomy of this genus is much better known than that of Cyrtona , the following description is principally limited to the male and female postabdomen.

The abdomen of the male is more cylindrical than that of Cyrtona . There is a single tergite between the large tergite 5 and the epandrium; it is tentatively identi ed here as tergite 7, with the tergite 6 atrophied.

Sternite 5 is large, and trough-shaped. Sternites 6 and 7 are small, variable and ill-de ned, but perhaps both represented, hidden by sternite 5. The hypandrium is trough-like; it helps to house the aedeagus when this is at rest, and guides its movement when in use.

The aedeagus (gure 8) has two valves, which are asymmetrical. The homologies are unclear, but it may be that one valve represents the fused parameres while the other is the main axis of the aedeagus; other interpretations are also possible. The aedeagus is carried on the end of a long curved aedeagal apodeme. Movement of the aedeagal apodeme results in the protrusion of the aedeagus, but there is a de nite limit to the degree to which this can be done. The resting state, and the maximum protrusion possible in Curtonotum quinquevittatum , are shown in gures 8a and 8b respectively. A membrane attached to the sleeve housing the aedeagal apodeme close to where the latter is slightly swollen, restrains further extension when a certain limit is reached. In gure 2 of McAlpine (1987), both the hypandrium and the aedeagal apodeme of C. helvum seem to be extended too far, thus making the aedeagal apodeme resemble an aedeagus. A ‘nodding’ type of articulation of the C. quinquevittatum aedeagus on its base, in the manner of Cyrtona , was not observed and would seem to be impossible.

The paired appendages of the male postabdomen are similar to those depicted for Curtonotum helvum in McAlpine (1987), but the interpretation oVered here is diVerent. The paired appendages next to the anal cerci in Curtonotum are here regarded as postsurstyli; the next pair of appendages are the presurstyli.

There is a minute ejaculatory sclerite (gure 6), from which the ejaculatory duct leads to the aedeagus and hence to the exterior, through the main shaft of the aedeagal apodeme which is proved thereby to be tubular. The tubular condition of the aedeagal apodeme may have led to misunderstandings of the nature of this structure in some accounts (e.g. McAlpine, 1987), in which it has been assumed that the main shaft of the aedeagal apodeme is a basiphallus, that is, a basal part of the aedeagus proper. Curtonotum is thus not the best representative of the family to use in order to determine homologies in this particular area. There is little musculature associated with the ejaculatory sclerite in this species, as the ejaculatory duct shows almost no swelling of its diameter here. I infer that the ejaculatory pump complex has no signi cant mechanical function. It is well innervated, however; it is likely that the ejaculatory sclerite serves mainly or solely as a platform for sense organs concerned with monitoring ejaculation, the ejaculation itself being driven by the more anterior parts of the ejaculatory system.

The testes (gure 7b) are long convoluted orange-brown tubes. The colour covers the testis uniformly, and there is no colourless apical part. Basally, one testis unites with its partner, to form what appears to be a single vessel, still having an orangebrown vestiture. Since the vessel clearly corresponds to a binary structure in Cyrtona , it is possible that it has a double lumen, but this has not been checked by sections. The median vessel is joined by the two very long convoluted colourless accessory glands, and together they debouche into the ejaculatory duct. The two shorter (type II) accessory glands noted in Cyrtona are not present.

The female abdomen (gure 9b) externally is rather unspecialized. Tergites 1–5 are large and well-formed. The last segments (6–8) form a moderately telescopic ovipositor, and the tergites and sternites of segments 6 and 7 are simple and undivided. The sclerites of segment 8 are rather indistinct. The cerci are simple, and not armed with specialized stout upturned setae as described and gured for Curtonotum helvum ( McAlpine, 1987) .

Internally, there is a pouch placed in the female tract, at the same position as the anteroventral brood pouch of Cyrtona . This structure might be a brood pouch also. Specimens have not yet, however, been dissected during the correct season (probably December–January, in northern Zimbabwe) to verify or dismiss the suspicion. In any case, Meier et al. (1997) clearly illustrated a pouch in the oviparous Curtonotum helvum , in which it is somewhat in ated, although eggs have not yet been found within the structure, and perhaps it is not used in this manner. Curtonotum cuthbertson i Duda (but possibly more correctly identi ed as C. sahelense Tsacas , according to Tsacas, 1977) is also known to be oviparous ( Greathead, 1958). The larval substrate is unknown for C. quinquevittatum .

The tarsi bear rows of short squat dual setulae.