Trichommation Engel, 2019

Engel, Michael S., 2019, A new genus of augochlorine bees from northern Venezuela (Hymenoptera: Halictidae), Journal of Melittology 2019 (87), pp. 1-15 : 4-7

Trichommation Engel , new genus

ZooBank: urn:lsid:zoobank.org:act:1EC370C1-806C-49C9-939D-65DE8CD215D2

TYPE SPECIES: Trichommation osculans Engel , new species .

DIAGNOSIS: Trichommation is unique among genera in the Megaloptidia -genus group for the possession of distinct ocular setae (most genera have minute setae, but these are about as long as a single ommatidial diameter, or often less, while in the new genus these setae are more than twice the ommatidial diameter, and often thrice or more). The new genus is most similar to Megommation and Megaloptidia , but differs from both in the pectinate inner metatibial spur (serrate in the former two genera), presence of basal rugae on the basal area of the propodeum (entirely coriarious without other sculpturing in the former two genera), and smaller body size (just under 10 mm in the new genus, while the former two genera are over 11 mm, and frequently 12–15 mm). Apart from the aforementioned traits, the combination of the following further discriminates the genus from others: ocelli enlarged; compound eyes not enlarged, with upper tangent not exceeding level of vertex; labral distal process narrowly triangular, narrower than basal area; labral basal area suborbicular; hypostomal ridge lamellate; probasitarsal brush present; and metabasitibial plate with all borders well defined.

DESCRIPTION: ♀: Mandible short (length from anterior articulation to apex subequal to lower interorbital distance: versus well surpassing it as in Cleptommation ), with acute subapical tooth. Labrum with distal process narrowly triangular, lateral teeth absent ( Fig. 7 ); basal elevation suborbicular, slightly protuberant, with apical surface flatened ( Fig. 6 ). Prementum greatly narrowed and elongate ( Fig. 4 ). Galeal apex acutely pointed ( Figs. 4 , 8 ). Hypostomal ridge lamellate, particularly strongly so posteriorly ( Fig. 8 ); anterior angle rounded. Malar space linear, base of mandible abuting lower tangent of compound eye ( Figs. 2 , 3 ). Epistomal sulcus forming orthogonal angle ( Fig. 3 ). Ocelli greatly enlarged ( Figs. 2 , 3 ); ocellar furrow absent; compound eyes not greatly enlarged, upper tangent not exceeding level of vertex in facial view ( Fig. 3 ); compound eyes with distinct ocular setae ( Fig. 9 ), individual setae longer than ommatidial diameter. Vertex not expanded or ridged posterior to ocelli, short (subequal to ocellar diameter), without ocellar furrow. Antennal flagellum with 10 flagellomeres. Preoccipital ridge rounded. Pronotal lateral angle obtuse, not projected, lateral ridge rounded, dorsal ridge not carinate. Mesoscutum broadly rounded anteriorly; mesoscutal lip low and rounded. Tegula oval. Probasitarsal brush absent. Scopa formed of long, plumose setae on metafemur, setae uniformly golden yellow ( Figs. 1 , 14 ); inner ridge of metatibia with long, branched setae blending to simple setae on outer surface; inner surface of metatibia with dense simple setae. Metabasitibial plate distinct on anterior and posterior borders ( Fig. 15 ), apex acutely rounded. Inner metatibial spur pectinate ( Fig. 16 ), fewer than 10 branches, branches not densely packed together. Forewing with marginal cell apex acute. Hind wing with distal hamuli irregularly spaced (2-1-2). Basal area of propodeum slightly shorter than mesoscutellum, surface coriarious (sensu Harris, 1979), with short, basal rugae ( Fig. 12 ), border between basal area and posterior surface broadly rounded; propodeal pit narrow, slit-like. Metasoma unmodified.

ETYMOLOGY: The new genus-group name is a combination of the Greek words trichós (genitive singular of thríx, meaning, “hair”) and ommation (diminutive of ómma, meaning, “eye”), and is a reference to the setose compound eyes, distinctive among the Megaloptidia -group of genera. The name also refers to the general similarity between this new taxon and the genus Megommation Moure. The gender of the name is neuter.

Figures

Figures 6–7. Labral and clypeal details from holotype female of Trichommation osculans, new ge- nus and species (clypeal angles of marginal area highlighted in green). 6. Direct view of clypeal apex and labral basal area. 7. Oblique view of clypeal apex and narrow labral distal process.

Figures 3–5. Holotype female of Trichommation osculans, new genus and species. 3. Facial view. 4. Ventral view of head. 5. Dorsal habitus.

Figures 8–9. Head details of Trichommation osculans, new genus and species. 8. Lateral oblique view of labiomaxillary complex and hypostomal lamella (arrow points to posterior enlargement of lamella). 9. Detail of compound eye showing fine ocular setae.

Figures 1–2. Holotype female of Trichommation osculans, new genus and species. 1. Lateral habitus. 2. Lateral detail of head and mesosoma.

Figures 14–17. Details of holotype female of Trichommation osculans, new genus and species, and Megommation insigne (Smith). 14. Hind leg of T. osculans. 15. Metabasitibial plate of T. osculans. 16. Inner and outer metatibial spurs of T. osculans. 17. Hind leg of M. insigne.

Figures 10–13. Details of holotype female of Trichommation osculans, new genus and species. 10. Forewing. 11. Detail of mesoscutum, mesoscutellum, and metanotum. 12. Detail of mesoscutellum, metanotum, and basal area of propodeum. 13. Detail of protibial calcar.