Research Article |
Corresponding author: Andrey I. Khalaim ( ptera@mail.ru ) Academic editor: Gavin Broad
© 2017 Andrey I. Khalaim.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Khalaim AI (2017) Contribution to the study of the genus Stethantyx Townes (Hymenoptera, Ichneumonidae, Tersilochinae), with description of a new species from Brazil. Journal of Hymenoptera Research 55: 129-138. https://doi.org/10.3897/jhr.55.5322
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A new species, Stethantyx durrelli sp. n. from Brazil, is described and illustrated. The recently described genus Megalochus Khalaim & Broad is synonymized with Stethantyx. The new species is very similar to S. grandis (Khalaim & Broad), comb. n. but differs by the first metasomal segment being trapeziform in cross-section, the presence of a distinct glymma, and the metapleuron and dorsolateral area of the propodeum being densely punctate, without coarse irregular rugae. These two species are the largest and most conspicuous representatives of the subfamily Tersilochinae. A partial key to species of Stethantyx is provided. Taxonomy and generic limits of Stethantyx are discussed.
Neotropical region, South America, Megalochus , taxonomy, new species, new synonymy, key
Stethantyx Townes is a large New World genus comprising 48 described and many undescribed species, most of which are Neotropical (
Nothing is known about the biology and host preferences of Megalochus but some species of Stethantyx were recorded as parasitoids of the beetle families Nitidulidae and Curculionidae (
The aim of this work is to describe a new species of Stethantyx from Brazil, reconsider the classification of Megalochus and provide a partial key to species of Stethantyx. The taxonomy of the genus Stethantyx is also briefly discussed.
Material of South American Tersilochinae from the Utah State University, Logan, Utah, USA (
Morphological terminology generally follows
The genus Megalochus was described for a single species, M. grandis, occurring from Costa Rica to southern Brazil. This genus was considered to be related to the large Neotropical genus Stethantyx, forming with the latter and the monotypic Australian genus Australochus Khalaim (
Megalochus | Stethantyx | |
Antenna | shortened; flagellomeres strongly transverse | not shortened; flagellomeres weakly transverse to elongate |
Propodeum and metapleuron | with coarse irregular rugae | without rugae |
Sub-basal cell in hind wing | unusually long and narrow | not especially narrow |
First metasomal segment | round in cross-section, very slender, about 6.6 times as long as posteriorly broad | trapeziform centrally in cross-section, 3.3–5.0 times as long as posteriorly broad |
Glymma | lacking | present |
A new species from southern and southeast Brazil, Stethantyx durrelli, intermediate between the genera Megalochus and Stethantyx, was recently discovered. This species is apparently closely related to M. grandis as both are almost identical morphologically and in coloration, except (suprisingly!) for two important diagnostic characters of the genus Megalochus: in S. durrelli, the glymma is present (Figs
1 | Fore wing with first and second abscissae of radius meeting at obtuse angle (Fig. |
2 |
– | Fore wing with first and second abscissae of radius meeting at right angle. Stethantyx radiata species-group |
See key to species by |
2 | Hind wing with mediella (M+Cu) very weakly arcuate and subparallel to submediella (1A), thus the sub-basal cell is unusually long, 5.0–6.0 times as long as broad (Fig. |
3 |
– | Hind wing with mediella (M+Cu) distinctly arcuate; sub-basal cell not unusually long, 2.8–4.0 times as long as broad. Small to moderately large species with body length usually 4.0 to 10.0 mm |
See keys to species by |
3 | First metasomal segment round in cross-section, without glymma. Metapleuron and dorsolateral area of propodeum with coarse irregular rugae. Fore wing with intercubitus about twice as long as abscissa of cubitus between intercubitus and second recurrent vein. Hind wing with nervellus slightly inclivous or vertical. Female with hind femur strongly clavate. Ovipositor with shallow dorsal subapical depression; sheath about 1.4 times as long as first tergite | S. grandis (Khalaim & Broad), comb. n. |
– | First metasomal segment trapeziform in cross-section, with a deep glymma (Figs |
S. durrelli sp. n. |
Stethantyx durrelli sp. n. is very similar to S. grandis but differs from it by the metapleuron and dorsolateral area of propodeum densely punctate on a finely granulate background (Figs
Female. Body length 13.0 mm. Fore wing length about 9.2 mm.
Head rounded posterior to eyes in dorsal view (Fig.
Notaulus rather long, weakly impressed, with a strong longitudinal wrinkle and sometimes with weak adjacent wrinkles (Figs
Fore wing (Fig.
Hind femur slightly clavate (Fig.
First metasomal segment very slender, 5.4 times as long as posteriorly broad, trapeziform in cross-section, arcuate in lateral view, smooth, with glymma situated somewhat behind its middle (Fig.
Head black; palpi, lower half of clypeus and mandible (except black teeth) brownish yellow. Antenna with scape and pedicel dark brown, flagellum black. Mesosoma (including tegula) black. Pterostigma pale brown. Legs brownish yellow; all coxae black; trochanters brown to brownish black; fore and mid femora brownish; hind femur brown, on lower and inner sides brownish black. Metasomal tergite 1 black, following tergites brown. Wings infumate with yellow-brown.
Male. Body length 10.5–13.0 mm, fore wing length 8.4–9.5 mm. Flagellum with 38 flagellomeres (Fig.
The male from São Paulo has metapleuron almost entirely covered with fine vertical wrinkles; dorsolateral area of propodeum with punctures mostly indistinct because of numerous fine wrinkles; basal area rather indistinct (basal longitudinal carinae weak); apical area hexagonal (apical longitudinal carinae ending anteriorly far from the posterior end of basal longitudinal carinae), impunctate; and nervellus less inclivous.
Holotype female (EMUS), Brazil, State of Rio de Janeiro, Teresópolis, 13.III.1966, coll. H. & M. Townes.
Paratypes. 1 male (FSCA), Brazil, State of São Paulo, Boracéia Biological Station, Sangre Grande, 18.XI.1976, coll. T. Rogers, 23KMPO93834. 1 male (EMUS), Brazil, State of Paraná, NE of Curitiba, Campina Grande do Sul, 16.II.1966, coll. H. & M. Townes.
Southern and southeast Brazil (Rio de Janeiro, São Paulo, Paraná).
The new species is named in honour of Gerald Durrell (1925–1995), a well-known British naturalist and author of many popular books about animals.
Stethantyx durrelli sp. n., female, holotype (15–18) and male, paratype (19–21): 15 first tergite, lateral view 16 glymma, lateral view 17 first and second tergites, dorsal view (the arrow points to the hind end of second tergite) 18 apex of ovipositor, lateral view 19 antenna, lateral view 20 propodeum, dorsolateral view 21 propodeum and first tergite, lateral view.
Originally,
Extensive study of Stethantyx in the past decade demonstrated a considerable morphological diversity of this genus, e.g. some species possess a right-angled radial cell, short and thick intercubitus and abscissa of cubitus between intercubitus and second recurrent vein, broad pterostigma, epicnemial (prepectal) carina with dorsal end obliterated and first metasomal segment without glymmae, and some undescribed species are not clearly distinguished from the genera Meggoleus, Probles Förster and Tersilochus Holmgren. Thus, most previously used diagnostic features of Stethantyx (
I am grateful to David Wahl (EMUS) and Kevin A. Williams (FSCA) for loan of valuable material, and Andrew Bennett (Canadian National Collection of Insects, Arachnids and Nematodes, Ottawa, Ontario, Canada) and Gavin Broad (The Natural History Museum, London, UK) for their important suggestions and criticism. Also I wish to thank Alejandro Zaldívar-Riverón (UNAM) for his kind help with taking high quality photographs. This work was supported by the Russian Foundation for Basic Research, grant no. 16-04-00197.