Oobius whiteorum Triapitsyn

Triapitsyn, Serguei V., Petrice, Toby R., Gates, Michael W. & Bauer, Leah S., 2015, Two new species of Oobius Trjapitzin (Hymenoptera, Encyrtidae) egg parasitoids of Agrilus spp. (Coleoptera, Buprestidae) from the USA, including a key and taxonomic notes on other congeneric Nearctic taxa, ZooKeys 498, pp. 29-50 : 38-41

Taxon classification Animalia Hymenoptera Encyrtidae

Oobius whiteorum Triapitsyn sp. n. Figures 11b, 26-29, 32, 35

Avetianella sp.: Loerch and Cameron 1983: 1798-1799 (egg parasitoid, host information); Trjapitzin 2001: 738 (list).

Type material.

Holotype female [UCRC] on slide (Fig. 11b) with following five labels: "USA, Pennsylvania, Venango Co., Bullion, 8.VII.1982, C. R. Loerch, Ex. Agrilus anxius Gory eggs", "Mounted by V. V. Berezovskiy 2014 in Canada balsam", " Avetianella sp. ( Encyrtidae ) Det. J. LaSalle", [magenta] " Oobius whiteorum Triapitsyn HOLOTYPE ♀", [database label] "Univ. Calif. Riverside Ent. Res. Museum UCRC ENT 401252". The holotype is in good condition, complete, dissected under 3 coverslips.

Paratypes: same data as the holotype, 4 ♀ on points and 1 ♂ on slide [UCRC].

Description.

FEMALE (holotype). Body somewhat flattened, dark brown to black; appendages brown except tarsi light brown; scape and pedicel a little darker than flagellum, and F6 just slightly lighter than other flagellar segments but still brown.

Frontovertex and mesonotum with faint mesh-like sculpture [very difficult to see in dry-mounted specimens]. Pronotum, mesoscutum, axillae, and scutellum with short, dusky setae; scutellum also with a pair of long, fine setae near posterior margin.

Head (Fig. 28) with ocelli in an obtuse triangle, posterior ocellus about its diameter away from eye margin. Transfacial and inner orbital sutures absent. Mandible 3-dentate; palpal formula 4-3.

Antenna (Fig. 26) inserted below lower eye margin. Radicle about 0.2 × total scape length, rest of scape slender, 4.1 –4.2× as long as wide, a little wider in the middle, with faint longitudinal sculpture. Pedicel longer than any funicle segment. F1-F3 about as long as wide, F4-F6 longer than wide; F1-F3 subequal, F4-F6 each progressively a little longer than the preceding funicle segment; F1-F3 without mps, F4 with 1 mps, F5 with 2 mps, and F6 with 3 or 4 mps. Clava 2.8 × as long as wide, and slightly shorter than combined length of F2-F6; each claval segment with 3 mps; apical claval segment obliquely truncate ventrally.

Mesosoma (Fig. 28) shorter than gaster. Mesoscutum about 1.6 × as wide as long. Scutellum wider than long, almost as long as mesoscutum.

Wings (Fig. 27) not abbreviated, forewing extending far beyond apex of gaster. Forewing 2.1 × as long as wide, hyaline; marginal setae very short; disc densely setose, linea calva interrupted posteriorly by rows of setae, filum spinosum present. Hindwing 3.7 –3.8× as long as wide, hyaline; longest marginal seta 0.18 × maximum wing width.

Mesotibial spur as long as mesobasitarsus.

Ovipositor occupying about 0.5 × length of gaster, exserted markedly beyond gastral apex (by 0.36 × total ovipositor length); ovipositor length:metatibia length ratio 1.3:1. Outer plate of ovipositor with 1 subapical seta.

Measurements of the holotype (mm, as length or length:width). Body (of the dry-mounted specimen prior to slide-mounting): 0.66; head: 0.19; mesosoma: 0.313; gaster: 0.35; ovipositor: 0.283. Antenna: radicle: 0.039; rest of scape: 0.151; pedicel: 0.06; F1: 0.021; F2: 0.021; F3: 0.021; F4: 0.028; F5: 0.035; F6: 0.044; clava: 0.155. Forewing: 0.677:0.314; longest marginal seta: 0.021; hindwing: 0.5:0.133; longest marginal seta: 0.024.

Variation (paratypes). Body (Fig. 35) length 0.66-0.75 mm (dry-mounted specimens).

MALE (paratype). Body length (of the dry-mounted specimen prior to slide-mounting) 0.66 mm. Head and mesosoma dark brown, gaster brown; scape and pedicel brown, flagellum light brown; legs light brown to brown. Antenna (Fig. 32) with scape minus radicle 3.2 × as long as wide; funicle segments longer than wide, more or less subequal in length (F5 and particularly F6 slightly longer), F1 and F2 without mps, F3 with or without mps, F4-F6 and clava with mps; flagellar segments with very long setae (slightly longer than each funicle segment’s width and about as long as width of clava); clava entire, 2.6 –2.7× as long as wide, a little wider than funicle segments. Mesosoma about as long as gaster. Forewing 1.9 × as long as wide, hyaline. Hindwing 3.5 × as long as wide, hyaline. Genitalia (Fig. 29) typical for the genus.

Diagnosis.

Among the Nearctic species of Oobius , Oobius whiteorum is most similar to Oobius dahlsteni , from which it differs by the proportions of the funicle segments of the female antenna, as indicated in the key. In Trjapitzin’s (2001) key to the world species of the former genus Avetianella (s. str.) in which this new species mostly fits, as characterised by Noyes (2010) in having the outer plate of the ovipositor being conspicuously distally elongate and ribbon-like and always with only a single subapical seta, it keys to Oobius dahlsteni . Oobius whiteorum differs from Oobius depressus , to which it is also somewhat similar, by a relatively less flattened body and by the much smaller body size in females; according to Girault (1916), the body length of the latter species is 1.15 mm. Oobius whiteorum differs from the North American species, but Neotropical species Oobius hasmik (Trjapitzin), known from Mexico ( Trjapitzin 2001) and also Costa Rica ( Noyes 2010), by the “closed” linea calva (Fig. 27) on the forewing ( “open”, not interrupted, in Oobius hasmik , Fig. 21) and also by the different proportions of the scape of the female antenna (Figs 26 and 20, respectively). In Noyes (2010), Oobius whiteorum keys to the same couplet with Oobius lutron Noyes from Costa Rica and Brazil, from which it differs by each of F4-F6 of the female antenna being of different length and longer than wide (Fig. 26) whereas in Oobius lutron F4-F6 are subequal and each quadrate or hardly longer than broad ( Noyes 2010).

Host.

Agrilus anxius Gory on European white birch ( Betula pendula ).

Etymology.

This species is named in honor of Lisa and Michael White of Chicago, Illinois, USA, good friends of the author’s family.

Comments.

According to Loerch and Cameron (1983), additional voucher specimens of the egg parasitoids of Agrilus anxius were deposited by them in PSUC; any of them belonging to this species are non-type specimens. Unfortunately, due to a renovation of the museum, point-mounted specimens in that collection are now inaccessible (A. Deans, personal communication).

The following paratypes [UCRC] of Oobius hasmik were examined, all collected at Las Barracas (~30 km E of Santiago, 23°28'02"N, 109°27'01"W, 50 m), Baja California Sur, Mexico: 1 ♀ on point with following five labels: "Mex. Baja Cal. Sur Las Barracas 17 - V - 1985", "Coll. P. DeBach Pan trap", " Avetianella ♀ Det. V. Trjapitzin May 1997", [red] "Paratypus ♀ Avetianella hasmik Trjapitzin", "Praep. micr. 22M" (an antenna, head, and a forewing were detached from this specimen; they are mounted on a slide with following two labels: " Avetianella hasmik ♀ Trjapitzin México: Baja California Sur, Las Barracas. Pan trap 17.V.1985 (Coll. P. DeBach) 22M Antena, cabeza, ala anterior", [red] "Paratypus Avetianella ♀ hasmik Trjapitzin"); also 16 ♀, 1 ♂ on points, all collected by P. DeBach during 1985 and 1986, as indicated by Trjapitzin (2001).