Lactistomyia Melander, 1902

Ale-Rocha, Rosaly, 2008, Revision of the Neotropical genus Lactistomyia Melander (Diptera, Hybotidae, Hybotinae), Zootaxa 1692, pp. 1-25 : 2-3

Lactistomyia Melander, 1902

Lactistomyia Melander, 1902:250 ; 1928:35 (key); Coquillett, 1903:251 (as subgenus of Hybos ); Bezzi, 1909:311 (discussion); Smith, 1967:14 (catalogue); 1977:188 (catalogue).

Type-species: Lactistomyia insolita Melander (monotypy).

Diagnosis. Robust species with thorax and abdomen densely pruinose; scutum strongly arched; proboscis long and rigid; labellum sclerotised without pseudotracheae; palpus long, flattened sidelong with dorsal preapical curved downwards bristle; antenna inserted in the middle of head; eyes holoptic on frons and narrowly dichoptic on face; face long; R4+5 and M1 usually convergent; hind femur swollen, strongly tuberculate and spiny beneath; hind tibia slightly arched to remarkably curved; tarsomere 1 of the hind tarsus rather conical, as long or longer than the following segments together, tarsomeres 2–4 shortened.

Body: 5.5 – 7.5 mm.

Redescription. Head slightly wider than high in frontal view. Eyes holoptic on frons. Upper facets slightly larger than the lower ones. Antenna inserted in the middle of head; postpedicel oval to oval-prolonged, with pointed apex, usually longer than the scape and pedicel together; arista apical, long and nude. Face long, eyes narrowly dichoptic on face. Proboscis long, surpassing the width of head; labellum sclerotised, without pseudotrachaeae, with short sensorial bristles. Palpus slender, laminate, as long as the proboscis, with dorsal preapical curved downwards bristle. Ocellar tubercle slightly protuberant with 1 pair of bristles. Post-cranium convex, pruinose; postocular setae uniserial, discontinuous, lacking in the middle of the post-cranium, upper setae longer than lower ones and bent forward; occipital setae present from the middle of the post-cranium to the buccal opening, disordered and more numerous inferiorly.

Thorax robust; scutum pruinose and densely setose, usually strongly prominent, also pyramidal. Thoracic setae thin, longer posteriorly, the anterior ones reclined and those of the prescutellar disc proclinate; acr multiserial forming a wide dorsal stripe; dc multiserial anteriorly, uniserial in the medium portion of the scutum, separated anteriorly from acr rows by narrow nude line and disordered, indistinct from acr setae on the disc; ial and spal abundant. Notopleuron setose. Pronotum with moderate length, with dorsal longitudinal suture and marginal setae. Laterotergite with short and dense pilosity. Outstanding bristles: 1 or 2 npl; 1 pal; 1 sctl subapical pair. Propleural seta absent.

Fore and mid leg slender, tarsi as long as the tibia. Hind leg robust, coxa with long bristles posteriorly, femur swollen; tibia slightly to remarkably curved, cylindrical or with anterior surface flattened with a soft longitudinal furrow and sharpened on the inner edge; hind tarsus short, one-half to two-thirds length of respective tibia; tarsomere 1 as long as or longer than following segments combined, tarsomeres 2–4 very short. Outstanding bristles: frequently 2–4 preapical bristles on fore tibia; several anterodorsal and some preapical on mid tibia; fore and mid tarsi with outstanding dorsal bristles; mid tarsomere 1 with ventral subbasal bristles; hind femur with ventral row of spines inserted on developed basal tubercles; hind tarsus frequently with anteroventral short spines.

Wing broad, apex usually slightly pointed; hyaline to brown. Stigma present or absent, usually fill out the apex of r1 cell. Sc incomplete. Rs short. R4+5 and M1 convergent. Discal cell long and narrow. Anal cell longer than the bm, with convex apex. Anal lobe developed. CuA2 weak.

Abdomen robust, cylindrical, pruinose. Bristles thin, Tg1 with long bristles, the following tergites with short bristles dorsally and elongate bristles on lateral margins, distinctly longer in the lateral of Tg2 and frequently Tg3. Tg8 short, sclerotised on approximately basal one-third and in lateral margins, the remaining membranous. Segment 8 slightly rotated for the right. Male terminalia asymmetric rotated 45 0–90 0 for the right. Epandrium divided dorsally; right lamella larger, left lamella distinctly shorter than the right lamella with numerous long and strong bristles near distal margin. Surstyli articulated, complex; right surstylus larger than the left. Hypandrium elongate. Postgonites asymmetric united basally forming a complete ring around base of phallus, expanded basally as a disk, more enlarged in the left postgonite; ventral apodeme short. Phallus short and robust, ventral ejaculatory apodeme developed and dorsal apodeme reduced. Cercus reduced. Female terminalia simple; cercus long.

Included species: Lactistomyia dimidiata (Bellardi) ; L. hyalia Bezzi ; L. insolita Melander ; L. lepida sp. n.; L. mammifera Curran ; L. minuta sp. n.; L. nigripes Curran ; L. paranaensis sp. n.; L. pulchra sp. n.; L. serrata Bezzi e L. tuberculata sp. n.. In the “A Catalogue of the Diptera of the Americas South of the United States ” Smith (1967) included the species L. panamensis Curran, 1931 . However Curran (1931) described only two species of Lactistomyia : L. nigripes and L. mammifera . In the page mentioned by Smith (1967) Curran described a species of Empis , E. panamensis ; therefore, Smith (1967) made a mistake changing the generic names.

Geographical distribution. The record of Lactistomyia for the Oriental Region ( Melander, 1928) was due to an identification mistake. L. polita Melander , described for that area, is not congeneric with Lactistomyia . Therefore, until the present, the genus is only registered in the Neotropical Region.

Discussion. The genus Lactistomyia Melander shares with Syndyas Loew , Syneches Walker , Hybos Meigen and Smithybos Ale-Rocha a long rigid proboscis, without pseudotrachaeae. Lactistomyia and Syndyas are most close. The distinction between Syndyas and Lactistomyia is, sometimes, difficult. Chvála (1975) and Ale-Rocha (1999) observed that some diagnostic characters of Syndyas , such as basal area of wing without microtrichia, vein M absent or inconspicuous, hind tibia clavate and hind tarsomere 1 dilated are variable in the genus, mainly in Neotropical and Afrotropical species. Besides, the most prominent characteristics of Lactistomyia , that took Melander (1902) to erect a new genus, are variable (not always the subsequent tibia, for instance, is distinctly curved, forms just slightly arched also happen in the genus), and sometimes are observed in Syndyas or other genera in Hybotinae (hind femur with tubercles at the base of the ventral spinelike bristles or spines is also found in some species of Syndyas , as well as in other genera of Hybotinae as commented by Coquillett [1903]). However, Lactistomyia can be distinguished from Syndyas by the following combination of characters (the states in Syndyas between parentheses): hind tibia slightly to remarkably curved (clavate); hind tarsomere 1 thin, longer or subequal to following tarsomeres combined (expanded, shorter than following tarsomeres combined, except S. subsabinios and S. amazonica [ Chvála, 1975; Ale- Rocha, 1999]); vein M normal (weak or absent); dm cell long (usually short) and base of Rs vein bent in obtuse angle (in right angle). The genus Lactistomyia includes great species, rarely smaller than 5.0 mm while the species of Syndyas are usually smaller. Lactistomyia can be distinguished from Syneches and Hybos by the long, narrow face, articulated left surstylus, short Rs vein and proclinate bristles on the disc; from Smithybos by the long face, articulated surstyli, scutum strongly prominent, acr rows multiserial and wide anal lobe.