Selitrichodes neseri Kelly & La Salle

Kelly, Janine, Salle, John La, Harney, Marlene, Dittrich-Schröder, Gudrun & Hurley, Brett, 2012, Selitrichodes neseri n. sp., a new parasitoid of the eucalyptus gall wasp Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae: Tetrastichinae), Zootaxa 3333, pp. 50-57 : 52-56

Selitrichodes neseri Kelly & La Salle , sp. nov.

Figs 2–11

Diagnosis. Selitrichodes neseri is the only known species of Selitrichodes with a distinctly infumated patch behind the marginal vein ( Fig. 7 ). Other diagnostic characters are forewing with 2 setae on submarginal vein and head and body almost entirely dark brown to black without yellow markings, except for the male where the face is yellow.

Description. Female ( Figs 2–8 ). Length 0.87–1.08 mm. Head black. Antenna with scape dark brown (may be lighter apically); flagellum brown. Mesosoma black; gaster dark brown. Coxae black (may be lighter apically); trochanters dark brown; femora dark brown to black; fore and middle tibiae light brown to yellow; hind tibia dark brown with apical third brown to yellow.

Head ( Fig. 4 ). Ocellar triangle without grooves. POL about 2.5 times as long as OOL. Scrobal area without distinct median carina; with a small transverse crack-like suture about halfway between frontal suture and torulus. Torulus level with ventral margin of eye. A broad depression (supraclypeal area) below torulus extending to clypeus and with some pilosity. Gena swollen and with malar sulcus somewhat curved near mouth margin. Clypeal margin bidentate.

Antenna ( Fig. 5 ) with 2 anelli, 3 funicular and 3 claval segments. First anellus longer than second. First and second funicular segments slightly longer than wide (F1 1.13–1.38; F2 2.00–1.38), third slightly wider than long to subquadrate (F3 0.90–1.2). Relative length of funicular segments to pedicel as follows: PDL: F1: F2: F3 = 1: 0.50–0.64: 0.55–0.60: 0.43–0.65. Clava 1.90–2.58 times longer than wide, wider than funicle, with terminal spine; C3 very short and its end broad, tapering slightly apically. Scape slightly flattened.

Mesosoma ( Fig. 6 ). Pronotum very short medially in dorsal view. Midlobe of mesoscutum with one row of 5 adnotaular setae on each side (some setae may form a partial second row). Scutellum with anterior pair of setae located behind middle. Dorsellum rounded posteriorly and overhanging propodeum. Mesosternum convex just in front of trochantinal lobes and without precoxal suture. Propodeum in dorsal view medially shorter than dorsellum. Propodeal spiracle with entire rim exposed and separated from anterior margin of propodeum by less than its largest diameter; rim of spiracle with a seta (seta of left spiracle broken in Fig. 6 ). Paraspiracular carina absent. Callus with 0 or 1 seta.

Forewing ( Fig. 7 ). Hyaline, with a distinct infumated patch behind marginal vein. Submarginal vein with 2 dorsal setae. Costal cell with one or more setae and a line of ventral setae near apex. Relative length of wing veins to stigmal vein as follows: CC: MV: STV: PMV = 2.83–4.33: 3.08–4.78: 1: 0.33–0.45: PMV one-third to just less than one-half length of stigmal vein. Speculum small and open posteriorly, the cubital line of setae not extending to basal line; speculum with one or more setae dorsally and with one to a few small setae on underside of wing. Wing disk beyond speculum densely pilose.

Metasoma ( Fig. 8 ). Gaster distinctly longer (1.56–1.66 times) than mesosoma . Hypopygium reaching less than half length of gaster. Cercus with 3 setae, subequal in length and slightly curved. Ovipositor sheath slightly protruding, short in dorsal view.

Male ( Figs 9, 10 ). Length 0.65–0.73 mm. Head dark brown to black, with yellow markings on lower face generally extending dorsally from mouth margin beyond toruli for about half distance to anterior ocellus, and laterally to inner eye margin and not reaching malar sulcus except in lighter specimens sometimes extending beyond malar sulcus onto gena. Antennae light yellow to white, funicle darker in some specimens. Legs light yellow to white, except for darker femora. Mesosoma and gaster dark brown to black, with base of gaster lighter. Gastral petiole very light yellow to white.

Antenna ( Fig. 10 ) with 2 anelli, 3 funicular and 3 claval segments. F1 and F2 quadrate to slightly longer than wide, F3 wider than long, with each successive segment increasingly broader. Funicle and clava without compact subbasal whorls of long setae. Scape with ventral plaque less than one-quarter length of and situated near apex of scape.

Material Examined. Holotype female ( ANIC): Laboratory reared at the Agricultural Research Council, Plant Protection Research Institute, emerged in culture x.2010 (originally from Australia, Queensland, Nanango, S. 26º41’19.3”S; E. 151º59’02.75”E, S. Neser, ex. leaf, petiole and twig galls on Eucalyptus sp., ix 2010).

49Ψ 115ɗ paratypes. Same data as holotype (49Ψ 54ɗ as follows: 17Ψ 24ɗ ANIC; 17Ψ 15ɗ SANC; 5Ψ 5ɗ BMNH; 5Ψ 5ɗ USNM; 5Ψ 5ɗ QMB); same data as holotype except emerged in culture ix.2010 (61ɗ ANIC).

Etymology. Named in honour of Stefan Neser, who first collected the species and provided valuable information on its biology.

Notes on biology. Specimens of S. neseri were exposed to ungalled Eucalyptus grandis x Eucalyptus camaldulensis (hybrid/clone number: GC540) potted plants to determine their possible role as a gall former or primary parasitoid. Unlike its congener S. globulus ( La Salle et al. 2009) , it was confirmed that S. neseri is not a gall former.

Selitrichodes neseri were reared on galled E. grandis x E. camaldulensis (GC540) potted plants in the FABI quarantine facility at an average room temperature of 26º C. Males and females were released into a sleeve enclosing the galled branches and leaves, and honey paper added to the sleeves to extend the longevity of adults. Galls exposed to S. neseri contained mature larvae or pupae of L. invasa . The sleeves were removed and the branches cut shortly before the anticipated emergence of the S. neseri offspring. Plant material was subsequently placed in large, unventilated polyethylene containers (“cake savers”) to allow monitoring of emerging specimens. Developmental time in the laboratory (egg-to-egg) ranged from 18–30 days. Selitrichodes neseri can be successfully reared under laboratory conditions, even in mature galls on severed shoots (Stefan Neser, pers com.), as is evident by the number of generations (10) and large numbers of adults reared within the first year. Dissections of L. invasa galls exposed to S. neseri showed single, relatively large eggs present externally on mature L. invasa larvae or pupae ( Fig. 11 ), as well as S. neseri larvae feeding on mature L. invasa larvae and pupae. This indicated that S. neseri is a primary parasitoid of L. invasa and not an inquiline.

Galls induced by Quadrastichus gallicola Prinsloo & Kelly on Erythrina lysistemon (Fabaceae) resemble galls of L. invasa , but were not found to be suitable for oviposition by S. neseri . More detailed studies of the biology and host range of S. neseri are underway.

The biological control of L. invasa has to remain a priority for all countries involved in the commercial production of susceptible species of Eucalyptus . Selitrichodes neseri is an additional parasitoid that shows much promise for biological control of this pest.

Figures

FIGURES 1, 2 (Photos: Stefan Neser): 1, Twig, petiole and leaf lamina galls as found at type locality on young plant of Eucalyptus sp.; 2, Selitrichodes neseri inserting ovipositor into a Leptocybe invasa gall on Eucalyptus grandis x Eucalyptus camaldulensis (GC 540).

FIGURES 3 – 8. Selitrichodes neseri female: 3, dosolateral habitus; 4, head in frontal view; 5, antenna in lateral view; 6, mesosoma in dorsal view; 7, wing in dorsal view; 8, metasoma in dorsal view.

FIGURES 9 – 11. 9 and 10, Selitrichodes neseri male: 9, dosolateral habitus; 10, antenna in lateral view. 11, Selitrichodes neseri eggs on a pupa of Leptocybe invasa (more than one egg probably a cage artefact) (Photo: Stefan Neser).