Syngaster Brullé, 1846

Iqbal, M., Austin, A. D. & Belokobylskij, S. A., 2006, Systematics of the Australasian endemic wasp genus Syngaster Brullé (Hymenoptera: Braconidae: Doryctinae), Journal of Natural History 40 (13 - 14), pp. 819-853 : 823-824

Syngaster Brullé

Syngaster Brullé 1846, p 454 . Type species: Syngaster lepidus Brullé by monotypy ( Viereck 1914); Turner 1918, p 57; Shenefelt and Marsh 1976, p 1332; Quicke et al. 1992, p 1021; Belokobylskij et al. 2004, p 100.

Epitonychus Szépligeti 1902, p 25 . Type species: Epitonychus υariegatus Szépligeti (synonymy by Fahringer 1942).

Diagnosis

Head subcubical. Ocelli small and in almost equilateral triangle. Antennal sockets situated very close together, sometimes almost fused along internal margins. Occipital carina usually present, sometimes absent. Eyes glabrous. Postgenal bridge narrow. Maxillary palps sixsegmented; labial palps four-segmented, third segment not shortened. Antennal scape long and narrow, with distinct constriction basally, with distinct apical lobe dorsally margined by two strong and widely separated lateral carinae, lower carina posteriorly not fused with upper. First flagellar segment weakly curved or straight, usually longer or sometimes shorter than second. Mesonotum high, rounded in lateral view and raised above pronotum. Notauli complete, usually shallow, sometimes deep. Prepectal carina present, postpectal carina absent, Sternaulus distinct and rather deep, almost straight. Propodeum without marginate areas, propodeal tubercles and propodeal bridge absent. Fore wing marginal cell slightly shortened, 2RS and r-m present, second submarginal cell short, 1m-cu almost interstitial, 1cu-a interstitial or postfurcal, first subdiscal cell closed distally, 3CU arising from posterior one-third to one-quarter along distal margin of first subdiscal cell. Hind wing subbasal cell short, m-cu present, basal cell wide distally, RS arising from R, marginal cell without r. Fore tibia with strong spines arranged almost in single row. Hind coxa usually angulate basoventrally but without tooth. Hind basitarsus 0.8–0.9 times as long as segments 2–5 combined. First metasomal tergite with small dorsope. Acrosternite 0.15–0.2 times as long as tergite. Second tergite with deep, curved basal furrow separating basal semicircular area, female with second suture distinct, almost straight or weakly curved laterally. Third tergite with distinct transverse, weakly curved furrow in basal one-third. Ovipositor longer than metasoma, usually almost as long as body.

Taxonomic comments

Syngaster annulicornis Brullé was excluded from the genus by Belokobilskij et al. (2004) and proposed as the type species of Pseudosyngaster Belokobilskij, Iqbal and Austin. The latter genus differs from Syngaster primarily in the second metasomal tergite lacking a semicircular basal area, the metapleuron being coarsely rugose-reticulate, and the metasoma lacking any white coloration. The placement of Syngaster as a junior synonym of Odontobracon Cameron by Szépligeti (1904) was not accepted by subsequent authors. Odontobracon is restricted to the New World, belongs to a different tribe, and is morphologically very different from Syngaster ( Marsh 1988) .

Hosts and biology

Host data are known only for S. lepidus which has been extensively reared from the larvae of Phoracantha spp. as a solitary idiobiont ectoparasitoid, as well as from the genera Coptocerus and Epithora (Cerambycidae) ( Austin et al. 1994; Belokobylskij et al. 2004). Syngaster lepidus has been introduced into South Africa and California as a biological control agent against Phoracantha attacking plantation and ornamental eucalypt trees. This species apparently did not establish in South Africa, but has in California where it is exerting some pressure, along with other introduced parasitoids, on Phoracantha populations ( Austin et al. 1994; Millar et al. 2002a, 2002b).

As outlined by Quicke et al. (1992), S. lepidus is part of a mimicry complex comprising species from three braconid subfamilies that parasitize the eucalypt wood-boring beetle genus Phoracantha in Australia. These wasps all have the same striking orange-red, black and white colour pattern. What is unclear is whether the other species of Syngaster that have a similar colour pattern (namely S. crypticus , S. polychromus , S. steυensi, S. tricolor , and S. υariegates) are also part of this mimicry complex and are parasitoids of Phoracantha spp. or related cerembycids.