Stethynium breviovipositor Huber, 2006

Huber, John T., Mendel, Zvi, Protasov, Alex & Salle, John La, 2006, Two new Australian species of Stethynium (Hymenoptera: Mymaridae), larval parasitoids of Ophelimus maskelli (Ashmead) (Hymenoptera: Eulophidae) on Eucalyptus, Journal of Natural History 40 (32 - 34), pp. 1909-1921 : 1916-1919

Stethynium breviovipositor Huber , n. sp.

( Figures 9–17 )

Type material

Holotype: female (ANIC), cleared and dissected under three coverslips on slide labelled: (1) ‘‘ Australia: NSW Wagga Wagga, ex. Ophelimus maskelli leaf galls on Eucalyptus camaldulensi s’’; (2) ‘‘em. from mature larvae vii. 2005 in quarantine culture, Bet Dagan Israel, Z. Mendel’’; and (3) ‘‘ Stethynium breviovipositor Huber Holotype female dorsal’’. Paratypes: 14 females and seven males pinned on cards, six females and two males on slides in Canada balsam (ANIC, BMNH, CNC, USNM).

Diagnosis

Ovipositor and sheaths short, arising midway along gaster at about level of apex of mesophragma ( Figures 11, 12 ); gaster with large orange inclusion internally near base of ovipositor; fore wing with lobe of posterior margin behind venation somewhat flattened ( Figure 1 ); anterior scutellum with narrow longitudinal median strip (5area between placoid sensilla on slide-mounted specimens) contrasting strongly with darker lateral areas, and the lateral areas contrasting distinctly with light-coloured posterior scutellum.

Among the species examined, none are similar to S. breviovipositor . All have either distinctly wider or narrower fore wings except S. flavinotae , which differs by its long, blacktipped ovipositor. No species has the large orange inclusion inside the gaster characteristic of S. breviovipositor . Stethynium ophelimi (described above) differs most distinctly from S. breviovipositor by its much longer, black-tipped ovipositor sheaths.

Description

Female. Body pale yellow to cream coloured. Eyes and ocelli grey, sometimes with a pink tinge. Trabeculae black. The following brown: mandible (especially the teeth), a minute area partly around each ocellus, a faint, diffuse area or, sometimes, more distinct small spot on each side of foramen magnum, anterior two-thirds of midlobe of mesoscutum, a spot medially on lateral lobe of mesoscutum, a spot on anterior margin of axilla and a paler one on posterior margin, anterior scutellum except for narrow, longitudinal median strip ( Figure 11 ), propodeum dorsally, and gaster dorsally, except laterally and sometimes also apically. A large orange inclusion inside gaster ( Figures 11, 12 ) often gives a greyish appearance (seen externally) to apicoventral part of gaster. Ovipositor scarcely darker than surrounding sterna. Wings uniformly hyaline, with venation light brown. Funicle and, especially, clava light brown to brown. Legs pale yellow, except for dark brown apical tarsomere of each leg.

Body length 585 (485–640, n 510, critical point-dried specimens). Head width 262 (224–292, n 55). Antenna ( Figure 5 ) with inner surface of scape transversely striate; funicle with all segments at least slightly longer than wide and without longitudinal sensilla; clava with six longitudinal sensilla. Length/width ratios (n 54 or 5, except scape52): scape 2.30–2.42, pedicel 1.43–1.59, fl 1 1.38–1.71, fl 2 2.13–2.48, fl 3 2.25–2.52, fl 4 1.85–2.35, fl 5 1.41–1.89, fl 6 1.54–1.96, clava 2.81–3.11. Measurements length (width) (n 55 or 6): 82–92 (31–37), pedicel 49–55 (25–36), fl 1 26–33 (17–19), fl 2 35–44 (15–18), fl 3 35–41 (15–16), fl 4 32–40 (16–20), fl 5 21–40 (19–23), fl 6 32–44 (19–25), clava 112–134 (38–44). Mesosoma with adnotaular seta slightly nearer anterior than posterior margin ( Figure 11 ). Posterior scutellum length/width50.69–0.78. Mesophragma posteriorly widely rounded ( Figure 11 ). Fore wing length (including humeral plate) 654 (587–730), width 238 (205– 268), length/width 2.76 (2.68–2.87, n 53), with discal microtrichia moderately sparse (especially behind stigmal vein), with lobe of posterior margin behind venation somewhat flattened ( Figure 9 ), and with longest marginal cilia 128 (124–136), just over half as long as wing width. Hind wing length 568 (502–654), width 44 (41–49), and longest marginal cilia 119 (108–129), about 2.7 times hind wing width. Metasoma with lateral margins of gaster more or less parallel-sided, converging to wide and blunt apex ( Figure 11 ). Ovipositor sheaths straight, evenly narrow along entire length ( Figure 12 ), and not exserted; ovipositor straight along its entire length and not extending beyond apices of sheaths ( Figures 11, 12 ).

Male. Body mostly black. Yellow (sometimes pale brown): face, most of vertex except around ocelli, gena, lower occiput, pronotal shoulders, narrow longitudinal median streak on anterior scutellum, posterior scutellum (especially lateral margins), and prosternum. Mesosternum varies from almost black to moderately light brown. Flagellum light brown.

Body length 605 (485–665, n 57, critical point-dried specimens). Antennal measurements (n 51, length only): scape 71, pedicel 43, fl 1 56, fl 2 61, fl 3 62, fl 4 67, fl 5 71, fl 6 70, fl 7 74, fl 8 75, fl 9 71, fl 10 73, fl 11 71. Length/width ratio of fl 6 1.94. Each flagellomere apparently with eight longitudinal sensilla. Genitalia with aedeagus, in lateral view, flattened dorsally and parameres at some distance from aedeagal apex ( Figures 16, 17 ).

Biology

Galls containing late second or third instar larvae were found to be suitable for successful development of Stethynium . A female wasp (the species could not be ascertained) inserts its ovipositor into the gall, most probably through a stomatal pore; these are found on both the adaxial and abaxial surfaces of the galls. Perhaps, S. ophelimi manages to parasitize second larvae of O. maskelli , reaching them with its relatively long ovipositor, whereas S. breviovipositor may only reach mature host larvae when they fill the gall chamber and are thus easier to reach with a short ovipositor. It seems that eggs and first instar larvae are ignored by the wasp, whereas the pupa is unsuitable for development. Stethynium survived for a relatively short period. Male and female survival seemed to be similar. Food has a significant effect on adult survival (F 7, 16526.9; P,0.0001, one-way ANOVA; SAS Institute 2002). Wasps fed with honey and water solution, with or without fresh young leaves present, lived for about 2 days. Wasps that were not given food or water, or that were given only water, or that were placed on leaves with galls 58–62 days after oviposition, survived for 1 day only. The low mean survival on galled foliage and Eucalyptus flowers suggests that neither nectar nor pollen feeding, nor host feeding occur.

Figures

Figures 8, 9. Stethynium spp. (8) S. ophelimi, male genitalia, dorsal. (9) S. breviovipositor sp. n., wings.

Figures 10–13. Stethynium breviovipositor, female. (10) Antenna. (11) Mesosoma and metasoma, dorsal. (12) Body, lateral. (13) Head, anterior.

Figures 14–17. Stethynium breviovipositor, male. (14) Antenna. (15) Mesosoma and metasoma, dorsal. (16) Mesosoma and metasoma, lateral. (17) Genitalia, lateral.

Figures 1–3. Stethynium ophelimi sp. n., female. (1) Wings. (2) Antenna. (3) Holotype, mesosoma+metasoma, dorsal.

Figures 4–7. Stethynium ophelimi. (4) Female body, lateral. (5) Holotype, head, anterior, and antenna. (6) Male head and antenna. (7) Male mesosoma and metasoma, dorsal.