Isomerocera Enderlein 1914
Creators: name: Mason, F.
name: Rozkošný, R.
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Stratiomyidae
Isomerocera

description: Genus Isomerocera Enderlein, 1914
Isomerocera Enderlein, 1914: 302.
Type species: Diphysa maculiventris Macquart, 1850 (= Stratiomys quadrilineata Fabricius, 1787), by original designation.
The external morphology of Isomerocera spp. corresponds with the groundplan of the diverse and extensive subfamily Pachygastrinae, which is characterised by the loss of vein M 3 in particular. Nevertheless, Woodley (2001) stated the instability of this character and concluded that the monophyly of the Pachygastrinae is only weakly supported on a world level. Isomerocera (Fig. 1) belongs to the group of pachygastrine genera distinguished by the following features: (1) some medial flagellomeres of the antenna have finger-like projections (Figs 31, 38, 45, 46, 64, 65), (2) the scutellum is armed with four strong spines (Figs 13–16), (3) vein R 2+3 arises beyond crossvein r-m, (4) vein R 4 is present (Fig. 4), (5) the abdomen is short and rounded, markedly convex dorsally (Figs 1–3) and (6) the male terminalia (Figs 6–8) show a unique parameral sheath. From these characters only characters (1) and (6) are apparently apomorphic though partly shared with Ptilocera (see Mason & Rozkošný 2011).
Head of Isomerocera (Figs 2, 30, 37, 44) holoptic in males and dichoptic in females, transverse in dorsal view and almost hemispherical, higher than long in lateral view, eyes bare in both sexes. Facets in upper part of male eye distinctly larger than in lower third, male ocellar triangle prominent in lateral view and frons divided by contiguous eyes into upper short part and lower, broader, subtriangular part, both covered with pale appressed hairs. Postocular area not visible in male but well developed in female. Female ocellar triangle is distinctly elevated above the level of eyes and this elevation visible also in front of the anterior ocellus as a preocellar tubercle (Figs 12 a, b). Female frons nearly parallel-sided, slightly narrower than scape is long. Antenna relatively long and slender, about 2–3× as long as head. Scape 3–4× longer than pedicel and pedicel cup-like, distinctly shorter than first flagellomere. Male flagellomeres 3–5 provided with paired finger-like projections, longer ventral and shorter dorsal ones. In females an additional, short ventral projection on flagellomere 2 distinct. Face slightly arched at middle below antennae. Proboscis (Fig. 25) unmodified and palpus two-segmented (Fig. 26).
Thorax without any apomorphic characters at generic level. Prealar prominence (Figs 21–23) present in front of wing base. Four strong marginal spines on scutellum of Isomerocera quadrilineata (Figs 15, 16) arranged in one plane but in two different planes in I. heteraspis (Figs 13, 14) (see James 1949 b). Wing venation (Figs 1, 4) characterised by vein R 2+3 arising beyond crossvein r-m and presence of R 4. Stronger veins in basal half of wing contrastingly pigmented and virtually all veins reach wing margin. Darkening on wing in front of crossvein r-m characteristic for both species. Wing membrane covered with dense microtrichia reduced in upper half of cup cell. Legs without any special structures, pretarsus corresponding with state found in all families of Homeodactyla (Fig. 27). In Isomerocera quadrilineata, extensive variation in leg colour pattern exists (see Figs 75–88).
Abdomen rounded and dorsally convex (Fig. 3). Silverish white hair patches on terga with extensively variable pattern (see Figs 42, 43, 59–61). Shape of male terminalia unique. Parameral sheath apparently bipartite (though connected by hyaline membrane) in both examined species of Isomerocera. Lateral projections of aedeagal complex unique within Pachygastrinae, represented by apically pointed appendages.
description: Published as part of Mason, F. & Rozkošný, R., 2015, Morphology, taxonomy, distribution and relationships of the Afrotropical genus Isomerocera (Diptera: Stratiomyidae), pp. 75 in African Invertebrates 56 (1) on pages 77-81, DOI: 10.5733/afin.056.0108, http://zenodo.org/record/7661835