Thyreodon walkerae, 2004

Gauld, Ian D. & Janzen, Daniel H., 2004, The systematics and biology of the Costa Rican species of parasitic wasps in the Thyreodon genus-group (Hymenoptera: Ichneumonidae), Zoological Journal of the Linnean Society 141 (3), pp. 297-351 : 326-327

10. THYREODON WALKERAE GAULD SP. NOV.

Fore wing length 19.9–20.5 mm; clypeus convex, with apex strongly pointed medially and conspicuously flared outwards; malar space 0.4–0.5 times basal mandibular width; maxillary palp long with second palpomere broadened and flattened; lower face centrally coriaceous to slightly rugose; frons with a pair of dorsally divergent crests between antennal sockets and with a sharp carina extending from outer rim of antennal sockets upwards, close to and parallel with eye margin; frons centrally weakly rugose; ocelli small, the lateral ocellus separated from eye by about 1.3 times its own maximum diameter; head in dorsal view punctate, with gena rather evenly rounded behind eye, occipital carina strong, its lower end sharp, abruptly in-turned but not reaching hypostomal carina; antenna setaceous, with 58–60 flagellomeres, the 20th slightly transverse, 0.9 times as long as broad, the subapical ones with setae which are shorter than the diameter of the flagellomere. Pronotum short with anterior margin strongly and broadly reflexed, and with posterior margin centrally swollen, forming a blunt angular ridge which is separated from the anterior margin by a deep U-shaped groove ( Fig. 26 ); epomia weak but discernible on upper part of pronotum; propleuron sparsely punctate, slightly convex, with lower corner flattened but not peripherally impressed; mesoscutum finely punctate, with broad, shallow, reticulated notauli which are confluent posteriorly, inner anterior margin of notaulus forming a sharp, high, transverse crest ( Fig. 38 ); scuto-scutellar groove very deep, laterally margined by a very strongly raised, simple carina; scutellum with close, fine punctures, convex; mesopleuron finely and sparsely punctate, with a shallow sternaular impression; metapleuron finely punctate with a few ridges anteriorly; propodeum laterally weakly flattened, quite finely reticulate, rounded and without a ridge above and behind the spiracle; propodeum posterodorsally reticulate, centrally with a single longitudinal impression. Fore leg of female rather stout, with coxa with a bluntly rounded protuberance behind trochanteral insertion, with 5th tarsomere about 0.9 times as long as preceding two tarsomeres, with tarsal claw long and with close pectinae; hind coxa in profile moderately small, its hind end more or less level with hind end of propodeum; hind femur slender, about 6 times as long as maximally deep; hind tarsus of male with moderately dense, coarse, long pubescence ventrally. Fore wing with abscissa of Cu 1a between Cu 1b and 2 m-cu 0.7–0.8 times as long as abscissa of Cu 1 between cu-a and 1 m-cu. Metasoma with tergite I slen- der, anteriorly subcylindrical; tergite II, in lateral view, 2.6–2.7 times as long as posteriorly deep. Male with subgenital plate small and convex, covered with dense coarse black hair; claspers quite long, the dorsal distal apex obliquely truncate, the lower margin slightly angulate near apex, but with apex without a broadly Vshaped indentation; dorsal margin with a deep median notch, basally slightly expanded; aedeagus in profile slender, with apex expanded, rounded on extreme apex, with a weak lateral keel.

A black species with proximal 0.6 or more of flagellum yellow-whitish; wings uniformly brownish black infumate.

Remarks: Thyreodon walkerae is named in honour of Annette K. Walker, in recognition of her identification of thousands of Microplitis wasplets ( Braconidae ) reared by the ACG caterpillar inventory. Thyreodon walkerae closely resembles two sympatric species, T. morosus and T. erythrocera , which are also black with black-tipped yellow-white antennae. It differs from T. morosus in having the propodeum, in lateral view, reticulate, and without a longitudinal ridge above and behind the propodeal spiracle. Unlike T. erythrocera , which has the anterior part of the notaulus more or less flat, T. walkerae has a pronounced transverse mesoscutal crest. It also differs from T. erythrocera in having the lower face coriaceous to rugose, rather than coarsely punctate, and in having the posterior ridge of the pronotum quadrate in profile, not overhanging the transverse groove.

Biological notes: Thyreodon walkerae is only known to occur in Costa Rica. Almost all individuals were collected or reared in the forest on Volcán Cacao in Sector Cacao of the ACG, although one adult has been taken on the Caribbean side of the country in Limón Province. T. walkerae has been reared on 60 occasions ( Table 1) from the larvae of Xylophanes hannemanni feeding on species of Rubiaceae , notably Coussarea austin-smithii (ten), Psychotria panamensis (nine), Psychotria sp. (six), Palicourea padifolia (six), Psychotria correae (five) and Psychotria eurycarpa (four) [96-SRNP-7049; 97-SRNP-1184; 97-SRNP-1189; 97-SRNP-1190; 97-SRNP-1211; 97-SRNP-1246; 97-SRNP-1276; 97-SRNP-1293; 97-SRNP-1303; 97-SRNP-1304; 97-SRNP-1306; 97-SRNP-1309; 97-SRNP-1348; 97-SRNP-1354; 97-SRNP-1355; 97-SRNP-1380; 97-SRNP-1385; 97-SRNP-1387; 97-SRNP-1400; 97-SRNP-1404.1; 97-SRNP-1419; 97-SRNP-1437; 97-SRNP-1441; 97-SRNP-1449; 97-SRNP-1473; 97-SRNP-1479; 97-SRNP-1512; 97-SRNP-1517; 97-SRNP-1535; 99-SRNP-766; 99-SRNP-852; 99-SRNP-1038; 00-SRNP-9644; 00-SRNP-9663; 00-SRNP-9674; 00-SRNP-9695.01; 00-SRNP-9713; 00-SRNP-9728; 00-SRNP-9731; 00-SRNP-9734; 00-SRNP-9744; 00-SRNP-9748; 00-SRNP-9761; 00-SRNP-9762; 00-SRNP-9791.1; 00-SRNP-9795; 00-SRNP-9808; 00-SRNP-9809; 00-SRNP-9813; 00-SRNP-9836; 00-SRNP-9840; 00-SRNP-9873; 00-SRNP-9876; 00-SRNP-9914; 01-SRNP-6941; 01-SRNP-6968; 01-SRNP-6971; 01-SRNP-6972; 01-SRNP-6973; 01-SRNP-6977]. The parasitoids kill their host as a prepupa and spin a cocoon in late June to early July, and emerge as adults the following year between late April and early June. This species is unambiguously univoltine, and adult wasps are present exactly during the peak availability of X. hannemanni caterpillars (which are approximately univoltine, despite their rain forest habitat). T. walkerae has never been encountered in more than 5 years of Malaise trapping in the exact forest understorey habitat that is rich in parasitized X. hannemanni caterpillars. Adults of what appear to be this wasp have been observed walking and flying clumsily among the understorey foliage during the daytime, apparently searching for host caterpillars.

We view T. walkerae as unambiguously a specialist on T. hannemanni caterpillars, because it has never been encountered in 370 rearings of 11 other species of Xylophanes (and many other sphingids) taken in the same sites (and often the same food plant) as the T. hannemanni caterpillars.

Material examined: Holotype ♀, COSTA RICA, Guanacaste Prov., Area de Conservacion Guanacaste, Sector Cacao, Sendero Arenales, eclosed 27 June 1998 (Franco) [97-SRNP-1387] ( JHVC) . Paratypes: COSTA RICA: Guanacaste Prov.: 1 ♀, Guanacaste National Park, Estacion Cacao , 1000–1400 m, v–vi.1990 (Guadamuz) ( INBio ) ; 22 ♀, 37 ♂, same locality, reared as per data listed above (Janzen & Hallwachs) ( JHVC) : Limón Prov.: 1 ♂, Rio Segunda & Rio Banano , 500 m, iv.1985 (Solís) ( INBio ) .

Figures

Figures 21–26. SEM photographs of Thyreodon spp., pronotum, lateral; 21, T. whitfieldi; 22, T. laticinctus; 23, T. darlingi; 24, T. rivinae; 25, T. morosus; 26, T. walkerae.

Figures 33–38. SEM photographs of Thyreodon spp. 33–36, propodeum, dorsal; 33, T. santarosae; 34, T. atriventris; 35, T. rivinae; 36, T. darlingi. 37–38, mesoscutum dorsal; 37, T. darlingi; 38, T. walkerae.