Ceratrichomyia Seguy

Reemer, Menno & Stahls, Gunilla, 2013, Generic revision and species classification of the Microdontinae (Diptera, Syrphidae), ZooKeys 288, pp. 1-213 : 22-24

Ceratrichomyia Seguy stat. n. Figs 46-58

Ceratrichomyia Séguy, 1951: 14. Type species: Ceratrichomyia behara Séguy, 1951: 14, by original designation.

Description.

Body length: 7-10 mm. Slender, black flies with yellow markings and a constricted abdomen. Head wider than thorax, face and vertex wider than an eye. Face ventrally produced in profile; wider than an eye. Lateral oral margins not produced. Vertex swollen. Occiput narrow ventrally, strongly widened dorsally. Eye bare. Eyes in male not approaching each other; smallest mutual distance much larger than width of antennal fossa. Antennal fossa about as high as wide. Antenna longer than height of head. Basoflagellomere at least three times as long as scape; with long pilosity. Postpronotum pilose or bare. Mesoscutum with transverse suture complete. Scutellum without calcars. Anepisternum with deep sulcus; entirely pilose. Anepimeron entirely pilose. Katepimeron convex; pilose or bare. Wing: vein R4+5 with posterior appendix; vein M1 straight, perpendicular to R4+5 and M; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located around basal 1/4 of cell dm. Abdomen constricted at segment 2. Tergites 3 and 4 not fused, able to articulate independently. Sternite 1 bare. Sternite 4 in male covered by genital capsule, therefore not visible without removing genitalia. Male genitalia: phallus straight or slightly bent dorsad, with spherical base very large, at least as long as remaining part of phallus; phallus furcate near apex; epandrium with or without ventrolateral ridge; surstylus deeply furcate.

Diagnosis. The combination of a complete transverse suture on the mesoscutum and a constricted abdomen is only found in Ceratrichomyia , Indascia Keiser, Indascia, 1958, Thompsodon gen. n. and certain species of Paramixogaster Brunetti, 1923. Males are easily distinguished from all these taxa by the long pilosity of the basoflagellomere, and also by sternite 4, which is covered by the genital capsule. From Paramixogaster this genus also differs by the unfused tergites 3 and 4. Females are unknown.

Discussion. Séguy (1951) attributed one species to this genus. He designated a male and a female as ‘types’, and another male as ‘cotype’. These are here all considered as syntypes. Examination of these three specimens made clear that they belong to three different species, which makes it necessary to designate a lectotype. The male with the following label data is here designated as lectotype. Label 1: "Madagascar, Behara"; label 2 (blue): "Museum Paris, III-38, A. Seyrig"; label 3 (red): “Type”; label 4: " Ceratrichomyia behara type du genre [male symbol] Séguy 50"; coll. MNHN. A redescription of the lecotype is given in the next section of the present paper. By this lectotype designation, the other two syntypes become paralectotypes. The male collected in Bekily (Madagascar) belongs to a new species of Ceratrichomyia , which is described in the present paper as Ceratrichomyia bullabucca spec. n. The female paralectotype, collected in Bekily, is here considered to belong to a previously undescribed species of Paramixogaster , because it possesses all characters described as diagnostic for that genus (see genus account). A description of that species is given under the name Paramixogaster piptotus sp. n. A third species attributed to this genus, Ceratrichomyia angolensis sp. n., is described from Angola.

The long pilosity of the male basoflagellomere was used by Séguy (1951) as a character to set his African genus Ceratrichomyia apart from other Microdontinae . This character is also present in Ptilobactrum Bezzi, 1915, another African taxon. Apparently Séguy was not aware of this, as he did not refer to Ptilobactrum . Cheng and Thompson (2008) did notice the similarity in antennal structure in both taxa and, based on the descriptions, proposed to regard Ceratrichomyia as a subjective junior synonym of Ptilobactrum .

Study of the type specimens of Ceratricomyia and Ptilobactrum revealed that these taxa are in fact very different. While Ceratrichomyia has, for instance, a constricted abdomen with unfused tergites 3 and 4, Ptilobactrum has a conical abdomen with fused tergites 3 and 4. The structures of the male genitalia are also very different (compare Figs 56-58 with 326), e.g. with a deeply furcate surstylus in Ceratrichomyia and an unfurcate one in Ptilobactrum . Considering these morphological differences, and supported by the phylogenetic results of Reemer and Ståhls (in press), Ceratrichomyia is here re-instated as a valid genus.

Diversity and distribution. Described species: 3. Two species are known from Madagascar, one from the African mainland (Angola).