Bassettia ASHMEAD, 1887

Melika, G & Abrahamson, WG, 2007, Review Of The Nearctic Gallwasp Species Of The Genus Bassettia Ashmead, 1887, With Description Of New Species (Hymenoptera: Cynipidae: Cynipini), Acta Zoologica Academiae Scientiarum Hungaricae 53 (2), pp. 131-148 : 132-135

Bassettia ASHMEAD, 1887

Bassettia ASHMEAD 1887: 146 ; ASHMEAD 1903: 155. Type species: Bassettia floridana ASHMEAD. Designated by ASHMEAD 1903: 155; WELD 1921: 232 (key to species).

Diagnosis – Closely resembles Plagiotrochus MAYR, 1881 , however, in Bassettia the malar space lacks radiating striae ( Fig. 2 ); the female fore wing margin without cilia ( Fig. 5 ); the median propodeal area is narrow, delimited by nearly straight or slightly outward curved lateral propodeal carina, without or with fragmented median longitudinal carina ( Fig. 6 ); 2nd metasomal tergite with a ring of dense white setae at the base, interrupted dorsally. In Plagiotrochus the malar space with radiating striae; the female fore wing margin with cilia; the central propodeal area is broad, limited by a strongly outward curved lateral propodeal carina, with complete or partially complete median longitudinal carina ( Fig. 7 ); 2nd metasomal tergite without a ring of dense white setae at the base. The asexual females of two Bassettia species ( B. ligni KINSEY and B. pallida ASHMEAD ) and two Plagiotrochus species (P. australis (MAYR) and P. marianii (KIEFFER )) share a unique character within the Cynipini : the vertex has a deep longitudinal depression from the median ocellus to the antennal sockets, with or without a carina at the bottom ( MELIKA et al. 2001).

Another closely related genus is Loxaulus MAYR, 1881 which can be easily distinguished from Bassettia by the structure of the propodeum being similar to Plagiotrochus and the mesoscutum is coriaceous ( MELIKA & ABRAHAMSON 2000).

Bassettia also resembles some Callirhytis FOERSTER, 1869 species, however, the head is higher or equal to its width; malar space without malar sulcus ( Fig. 2 ); the mesosoma is compressed dorso-laterally, usually 1.3–1.5 times as long as high in lateral view; the mesoscutum 1.5–2.0 times as long as broad (Figs 11–13), while in Callirhytis the head is transverse, broader than high; malar space with strong malar sulcus (Fig. 14); the mesosoma is arched, if slightly compressed dorso-laterally, then less than 1.2–1.3 times as long as high in lateral view; the mesoscutum is equal or only slightly longer than broad.

Redescription – Female. Head 2.0–2.5 times as long as broad from above, nearly as high as broad or slightly higher than broad in front view, rounded, never trapezoid; gena broadened behind eye, equal or slightly broader than cross diameter of eye ( Figs 1–2 ); eyes slightly or not converging inward. POD longer or equal to OOD. Occiput, vertex, frons, and gena behind eye finely alutaceous; vertex with or without median longitudinal depression running from median ocellus to antennal sockets and with or without longitudinal carina on its bottom. Lower face with uniform dense short white setae which partially hide coriaceous sculpture. Malar space without sulcus, with a similar sculpture as the lower face, without radiating striae, rarely with faint striae. Anterior tentorial pits deep; clypeus small, rounded, with white short setae. Distance between antennal sockets smaller than distance to eye. Antenna 14-segmented, usually as long as head and mesosoma together. Scape and pedicel strongly flattened, scape nearly as long as broad; F1 longest, nearly as long or longer than scape and pedicel together. F1–F4 filiform, much longer than broad; F5–F10 much shorter, subequal, broader than the previous flagellomeres (Fig. 15). Mesosoma flattened dorso-ventrally (Fig. 11), elongated; notauli complete or incomplete, present at least in posterior 2/3 of mesoscutum, absent in some specimes; parapsidal lines distinct, anterior parallel lines present, indistinct or absent (Figs 12–13). Mesoscutum transversely rugose or finely coriaceous, at least inward of parapsidal lines; transverse sculpture always traceable. Mesoscutellum usually uniformly coriaceous, very slightly overhanging metascutellum, usually with shallow smooth, shiny foveae separated or not by median carina; sometimes foveae are in the form of narrow shiny smooth stripe without median carina. Propodeum with a narrow central shiny area, delimited by two straight nearly parallel or slightly outward curved lateral propodeal carinae; median longitudinal carina very fragmented, indistinct or absent, sides of propodeum outward of central area densely pubescent ( Fig. 6 ). Nucha with longitudinal striae. Fore wing nearly as long as the body, margin without cilia, veins brown or pale, areolet present or absent ( Fig. 5 ). Tarsal claws simple, without basal lobe. First prothoracic tarsomere elongated, nearly equal to subsequent three tarsomeres together. Metasoma elongated, 2nd abdominal tergite occupies half the length of metasoma, with a ring of dense white setae at base, interrupted dorsally (Fig. 16). Prominent part of ventral spine of hypopygium always longer than broad, with few sparse white setae reaching beyond apex of metasoma (Fig. 16). Length is 3.0– 5.5 mm.

Male. Antenna 16-segmented, F1 straight or only very slightly curved, not or slightly incised and broadened apically (Fig. 9). Mesosoma longer than metasoma ( Fig. 18 ). Fore wing margin with cilia, veins pale, indistinct ( Fig. 17 ). 2nd metasomal tergite with few sparse white hairs at base. Otherwise, similar to the female.

Gall. The asexual generation induces stem galls which develop in twigs, hidden under the bark, in the form of elongated larval cells which usually do not cause swellings ( Fig. 8 ). Thus, the only evidence of galling is typically the adults’ emergence holes. The sexual generation induces small oval swellings on leaves, which protrude from both leaf surfaces.

Comments – Previous limits of the genus Bassettia were imprecise as Bassettia included four Callirhytis species that shared some morphological characters thought to be diagnostic for the Bassettia genus. Four species from Bassettia were transferred to Callirhytis : C. aquaticae (ASHMEAD) , C. ceropteroides (BASSETT) , C. herberti (WELD) , and C. quercuscatesbaei (ASHMEAD) ( MELIKA & ABRAHAMSON 2002) .

Distribution – Currently five Bassettia species are known, all from North America north of Mexico. Biology – Alternate asexual and sexual generations are present. ROSENTHAL and KOEHLER (1971) and EVANS (1972) described the sexual generation of B. ligni KINSEY. The present authors also found sexual Bassettia in Florida.

pallida , 7 = Plagiotrochus quercusilicis. 8 = Bassettia ligni , galls

WELD (1921) published a key to four Bassettia species. And, WELD also produced a manuscript key to Bassettia that included all the known species as well as a number of undescribed species (this manuscript key is on file at the USNM). We credit WELD’ s useful notes and manuscript keys to Cynipoidea . Below, we offer a key to the eight valid Bassettia species, including the new ones.

Figures

Figs 1–8. 1–2 = Bassettia pallida, head: 1 = from above, 2 = front view. 3–4 = Plagiotrochus quercusilicis, head:3 = from above, 4 =front view. 5 = Bassettia tenuana, fore wing. 6–7 = propodeum:6 = B.

Figs 17–23. 17–19 = Bassettia archboldi: 17 = fore wing, 18 = body, lateral view, 19 = scutum and scutellum, dorsal view. 20–21 = female antenna: 20 = B. virginiana, 21 = B. pallida. 22–23 = scutum