Diachasma

Shirley, Xanthe, Restuccia, Danielle, Ly, Andrew & Wharton, Robert, 2014, A new opiine (Hymenoptera, Braconidae) from Australia with discussion of Diachasma Foerster, ZooKeys 437, pp. 33-44 : 36-38

Taxon classification Animalia Hymenoptera Braconidae

Diachasma

Diachasma Foerster, 1862: 259. Type species: Opius fulgidus Haliday, 1837. Monobasic and original designation.

Atoreuteus Foerster, 1862: 241. Type species: Atoreuteus striatus Foerster, 1862. Monobasic and original designation. Synonymized by Fischer (1971).

Bathystomus Foerster, 1862: 235. Type species: Bathystomus xanthopus Foerster, 1862. Monobasic and original designation. Synonymized by Fischer (1971).

Lytacra Foerster, 1862: 258. Type species: Lytacra stygia Foerster, 1862. Monobasic and original designation. Synonymized by Wharton (1987).

Alysopius Tobias, 1976: 76-77. Type species: Alysopius compressiventris Tobias, 1976. Monobasic and original designation. Synonymized by Fischer (1986).

Diagnosis.

Ventral margin of clypeus even, without teeth or tubercles, truncate to weakly concave; labrum usually flat, always broadly exposed. Occipital carina broadly absent dorsally, present laterally, extending to base of mandible, widely separated from hypostomal carina. Notauli varying from nearly absent to complete and ending in mesoscutal midpit, often sculptured anteriorly; mesoscutal midpit present, varying from punctiform to narrowly elongate. Precoxal sulcus varying from unsculptured and nearly absent to crenulate and extending nearly full length of mesopleuron. Fore wing stigma broad, discrete, with r1 arising from or distad midpoint; second submarginal cell relatively short, with 2RS and 3RSa approximately equal in length; m-cu antefurcal to postfurcal; RS complete to wing margin; 1st subdiscal cell closed (2cu-a present). Hind wing RS poorly developed, often barely indicated distally; m-cu nearly always present, though often weakly developed. First metasomal tergite with or without dorsope. Metasomal tergum 2+3 either smooth or sculptured. Ovipositor sheath varying from barely exserted to extending 0.5 × length of metasoma.

Remarks.

Fischer (1971) placed Atoreuteus and Bathystomus as synonyms of Diachasma , but both have been treated separately in subsequent studies ( Wharton 1988, Quicke et al. 1997). Belokobylskij et al. (2003) listed them under Diachasma , with a note that not all authors agreed with this placement. Yu et al. (2012) also left them in Diachasma . Wharton (1988) noted major differences in external morphology between Atoreuteus and Bathystomus , and these were corroborated by venom gland differences observed by Quicke et al. (1997). Similarly, Wharton (1988) described differences in labral and mandibular morphology that differentiate these two from more typical Diachasma . The type species of both Atoreuteus and Bathystomus also have an exceptionally large pronope. Their placement remains enigmatic, though the shape of the labrum suggests a basal position within Opiinae . They likely merit recognition as separate genera, but we leave them in Diachasma , with reluctance, pending a more rigorous analysis of opiine relationships.

The new species described below belongs to an Australian/New Guinea species group that is also morphologically distinct from typical members of Diachasma (as represented by species such as Diachasma fulgidum and Diachasma hispanicum (Fischer)). These austral species include Diachasma australe (Fischer), Diachasma extasis Fischer, Diachasma kaltenbachi Fischer, and Diachasma tasmaniae Fischer. This group can be characterized as monophyletic by the distal origin of r1 from the stigma (distinctly beyond the midpoint). The included species can be further recognized by the combination of a postfurcal fore wing m-cu, propodeal sculpture with well-developed median longitudinal carina on anterior half, bordered by relatively unsculptured areas, and T1 with well-developed dorsope. Most species also have fore wing 2CUa shorter than 2cu-a.

The type species, Diachasma fulgidum , is unusual in lacking a well-defined malar sulcus and having a relatively flattened scutellum with polished posterior margin.

Species excluded.

Specimens of the species newly described below were compared to primary types and other specimens of nominal species of Diachasma previously described from Australia and New Guinea. During this examination, we discovered that a specimen in HNHM labeled as the lectotype male of Diachasma rufipes Szépligeti, 1905, is a member of the genus Notiopambolus van Achterberg & Quicke. The new combination is Notiopambolus rufipes ( Szépligeti). Several species of Notiopambolus have been described from eastern Australia ( van Achterberg and Quicke1990, Belokobylskij 1992). It is likely that rufipes is a senior synonym of one of these previously described species, but we are unable to place it at this time.

Key to species of Diachasma known from Australia and New Guinea