Curtonotidae

Pollock, J. N., 2002, Observations on the biology and anatomy of Curtonotidae (Diptera: Schizophora), Journal of Natural History 36 (14), pp. 1725-1745 : 1740-1742

Curtonotidae : its status relative to Ephydroidea sensu lato

The following lists some of the derived features of Curtonotidae , relative to the ephydroid ground plan given above:

(i) only two spermathecae present;

(ii) protrusible aedeagal apodeme present;

(iii) 7th tergite of the male abdomen larger than the 6th (it is possible that this feature relates to Cyrtona only, rather than the family Curtonotidae ).

I agree with Meier et al. (1997) that, from the evidence they present, the so-called third spermatheca of Axinota that has been reported (Del nado, 1969) appears to be a sclerotized ventral receptacle of unusual shape. To say that two spermathecae only are present in the ground plan of Ephydroidea is perhaps premature, however, because three are present in Oestridae and in certain hippoboscids; these ies are considered here to be derived from early ephydroids.

Cyrtona is unusual and perhaps unique within Ephydroidea sensu stricto in the following ways:

(i) It has a symmetrical, articulating aedeagus on a raised pedicel formed by the aedeagal apodeme and ensleeving cuticle. This is a primitive feature in this context, being reported and evaluated here for the rst time for any Ephydroidea sensu stricto, and it is similar to the condition in many other acalyptrate families as well as in Glossina . The Curtonotum striatifrons species group may t the same description, however (see gures 5, 11 and 12 in Tsacas, 1977), except that the aedeagus in such cases is apparently asymmetrical; in C. platyphallum Tsacas (loc. cit. gure 6) the aedeagus might even be symmetrical. In contrast to the above description, McAlpine (1989) described the ground plan ephydroid aedeagus as being ‘...rather short, rigid, and in a relatively xed position’, but the reasons for this characterizatio n were not stated. The identi cation of the aedeagus articulating on a long pedicel as a primitive feature, calls for a reappraisal of the corresponding structure in Glossina , which was seen earlier ( Pollock, 1973) as a modi cation of the male consequent upon the loss of the narrowed terminal female abdominal segments. Glossina can now be regarded as retaining an important primitive feature in this regard. Although both Glossina and Cyrtona are larviparous, Curtonotum is not (as far as is known) and the elongate pedicel on which the aedeagus sits is present in this genus, showing that the aedeagal con guration in question is not to do with larviparity. The fusion of tergites 6 and 7 of the male abdomen in some members of Drosophilidae now appears to be a neomorph as the tergites are not fused in Cyrtona , and therefore presumably not in the ground plan of Ephydroidea (cf. Pollock, 1999: 785).

(ii) The architecture of its male postabdomen includes separate, well-formed and symmetrical tergites 6 and 7; a large symmetrical sternite 6; and a possible remnant asymmetrical sternite 7.

Also regarded as primitive in the context of Ephydroidea are the additional following features, shared with other curtonotids: the subcosta reaching the wing margin independently of vein 1 (R1), and the tarsi having lines of dual setulae. In contrast with the notion that the last character is primitive, Grimaldi (1990) believed that the lines of dual setulae (lines of cuneiform setae, in his terminology) evolved as neomorphs at least three times within Ephydroidea, but in view of the other evidence presented in the present paper, this seems unlikely.

I suggest that, after making due allowances for the presence of larviparity (male anatomy may also be involved to some extent, such as the loss of the postsurstyli), and the derived curtonotid features listed at the beginning of this section, Cyrtona may be regarded as a specially valuable outgroup comparator for studies in the evolution of other ephydroid groups such as Drosophilidae ( Grimaldi, 1990) , having some advantages over Curtonotum in that role.