Colonomyia COLLESS , 1963

Jaschhof, Mathias & Jaschhof, Catrin, 2008, The Ohakunea group in Tasmania, with description of Colonomyia tasmanica sp. n. (Diptera: Sciaroidea), Beiträge Zur Entomologie = Contributions to Entomology 58 (2), pp. 441-453 : 444

Genus Colonomyia COLLESS, 1963

COLLESS 1963: 305, MATILE &TURET 1994, HIPPA &ZASCHHOF 2004, AMORIM & RINDAL 2007: 15.

This genus has an amphinotic distribution ( MATILE & DURET 1994) with six species found in the Neotropical region and three species, including tasmanica sp. n., in the Australasian region. The Neotropical species, with the possible exception of obtusistyla MATILE & DURET , belong to a lineage distinct from the Australasian species ( HIPPA & JASCHHOF 2004). The position of obtusistyla , with regressive adult morphology, is still obscure. The Australasian lineage ( Colonomyia sensu stricto) is characterized as follows ( HIPPA & JASCHHOF 2004, this paper): the setose portion of face is small; the microtrichia on postnotum are large and clustered in circular groups; the number of pale setiform sensilla on the basitarsi is small, i. e. not exceeding five; the apical portion of CuA2 is slightly sinuous; the male tergite 9 is two-lobed; the sperm sac is large, slightly sclerotized, and has a large pubescent bulge close to the primary gonopore; the male sternite 10 is subtriangular; and the female sternum 8 has laterally a sclerotized interior brace. One may expect that when the terminalia of the Neotropical species are studied to the same detail as done here, further differences will appear between the Neotropical and Australasian lineages. Moreover, one may anticipate the generic separation of these two lineages, which will require resolution of the position of obtusistyla .

The male terminalia of Colonomyia s. str. spp. are peculiar for the presence of the large, elaborate sperm sac with a tubular posterior extension, the endophallus ( Fig. 2 ). This is not described for any of the Neotropical species, nor could we observe it in the specimens we have at hand of borea HIPPA & JASCHHOF , of an unnamed species near borea , and of magellanica MATILE & DURET. The sperm pump of Colonomyia s. str. ( Fig. 1B ) has a configuration similar to that in some basal Brachycera (cf. SINCLAIR 2000: figs 20-23) and should function accordingly, i. e. by the ejaculatory apodeme, even though not particularly broad, compressing the sperm sac. The ejaculatory apodeme of Colonomyia s. str. bears three muscles (mI-mIII): mI leading from the apodeme base to the parameres; mII from the apodeme base to the ventrobasal rim of gonocoxites, and mIII from the longitudinal carina to the apical portions of the gonocoxal apodemes. Speciesspecific modifications of this pattern include: mI that in tasmanica has a fascicle leading to the basal portions of the gonocoxal apodemes, and mIII that in albicaulis has a fascicle inserted on the apex of the ejaculatory apodeme. It is likely that the “head-like extension of the ejaculatory apodeme” ( HIPPA & JASCHHOF 2004) is completely or partially referable to the aedeagus, viz. its sclerotized apex.

Quite unusual for Sciaroidea, in Colonomyia s. str. the elaborate, highly flexible construction of the male copulatory organ has a counterpart in the female, which is composed of derivatives of the ninth segment. Of that segment, the tergite, largely internalized, and the gonapophyses form together a complex, expansive apparatus, which occupies the dorsal and posterior walls of the genital chamber. Rigid, sclerotized parts are interlinked through soft connective tissue, which form an apparently quite flexible structure supported by several muscles. In the two Australian species, albicaulis and tasmanica , of which this apparatus has been studied in some detail, its construction is definitely species-specific. One may assume that there is a tight mechanical fit between the male and female structures, but pairs in copula, which might furnish proof, have not yet been found.

Figures

Fig. 2: Colonomyia tasmanica sp. n., paratype male; terminalia, ninth tergite and adjacent structures omitted, dorsal view. 1 = gonocoxite, 2 = gonocoxal apodeme, 3 = gonostylus, 4 = dorsomesal lobe of gonostylus, 5 = paramere, 6 = ejaculatory apodeme, 7 = endophallus, 8 = primary gonopore, 9 = phallotrema, 10 = pubescent bulge, 11 = sperm sac. Length of scale bar = 0.05 mm.

Fig. 1: Colonomyia tasmanica sp. n., paratype males. - A: terminalia, ninth tergite and adjacent structures omitted, ventral view; - B: terminalia, lateral view. 1 = gonocoxite, 2 = gonocoxal apodeme, 3 = gonostylus, 4 = ninth tergite, 5 = paramere, 6 = ejaculatory apodeme, 7 = endophallus, 8 = pubescent bulge, 9 = sperm sac, 10 = tenth sternite, 11 = cercus. Length of scale bar = 0.1 mm.