Thyreodon rufothorax, 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 : 337-339

20. THYREODON RUFOTHORAX CAMERON STAT. NOV.

Thyreodon rufothorax Cameron, 1886 : plate 12. Holotype ♀, PANAMA (BMNH) [examined].

Thyreodon rufithorax Cameron : Cameron, 1886: 290. [Mis-spelling of rufothorax .]

Tipulophion rufithorax (Cameron) Schulz, 1903: 249 . [Mis-spelling of rufothorax .]

[ Thyreodon atriventris (Cresson) Townes & Townes, 1966: 186 . Misidentification.]

Fore wing length 20.7–22.2 mm; clypeus rather flat, with apex out-flared, with a rounded point medially; malar space more or less obliterated; maxillary palp long, with second palpomere strongly broadened and slightly inflated; lower face centrally finely punctate; frons with a single weak vertical crest between antennal sockets and without a low carina extending from outer rim of antennal sockets upwards, close to and parallel with eye margin; frons centrally rugose; ocelli very large, the lateral ocellus contiguous with eye; head in dorsal view with gena rather evenly rounded behind eye, occipital carina strong, its lower end sharp, but not reaching hypostomal carina; antenna setaceous, with 53–54 flagellomeres, the 20th slightly elongate, 1.1–1.2 times as long as broad, the subapical ones with setae which are longer than the diameter of the flagellomere. Pronotum short with anterior margin strongly and broadly reflexed, and with posterior margin centrally weakly swollen, forming a low rounded ridge which is separated from the anterior margin by a deep U-shaped groove; epomia absent; propleuron sparsely punctate, with lower corner rounded, peripherally not impressed but slightly flared outwards; mesoscutum finely and sparsely punctate, with narrow, shallow, slightly transversely striate notauli which are almost confluent posteriorly, inner anterior margin of notaulus unspecialized; scuto-scutellar groove moderately deep, long, laterally margined by thickened, simple carinae; scutellum smooth, very finely punctate, rather flat; mesopleuron finely punctate, usually with a rather shallow sternaular impression, sometimes this impression obsolescent; metapleuron finely punctate to granulate, with a few rugae dorsally; propodeum laterally slightly flattened, very coarsely reticulate, with a sharp strongly raised tubercle above and behind the spiracle; propodeum posterodorsally very coarsely reticulate, centrally without a trace of a shallow longitudinal impression. Fore leg of female rather slender, with coxa with a very low, bluntly rounded protuberance behind trochanteral insertion, with 5th tarsomere 0.5–0.6 times as long as preceding two tarsomeres, with tarsal claw long and with fine, close pectinae; hind coxa in profile moderately large, its hind end projecting well behind level of hind end of propodeum; hind femur slender, about 6 times as long as maximally deep; hind tarsus of male with dense, moderately long pubescence ventrally. Fore wing with abscissa of Cu 1a between Cu 1b and 2 m-cu 1.50–1.60 times as long as abscissa of Cu 1 between cu-a and 1 m-cu. Metasoma with tergite I moderately slender, anteriorly subcylindrical or slightly dorsoventrally depressed; tergite II, in lateral view, 1.5–1.7 times as long as posteriorly deep. Male with subgenital plate small and convex, with rather sparse hair; claspers quite long, the dorsal apex produced into a short spine-like projection, the lower margin rounded, not angulate before apex; aedeagus in profile with apex expanded, apically weakly flattened, with a sharp lateral keel.

A mainly orange-brown species with interocellar area, flagellum, metasoma, and hind leg blackish brown, fore and mid tarsus slightly infuscate; wings hyaline with basal cell, distal 0.5 or so of marginal cell and proximal part of 3rd submarginal cell blackish infumate.

Remarks: Thyreodon rufothorax is easily separated from most other Thyreodon by the combination of its very large ocelli and eyes (which are contiguous, and the latter occlude the malar space almost entirely), coloration and pattern of the fore wings ( Fig. 9 ). However, in these features and most others, it closely resembles T. atriventris and the two species are widely intermingled in museum collections of wild-caught ‘ T. atriventris ’; it was discussed under this species earlier ( Gauld, 1988). Both sexes of the two species are most easily separated by the wing colour pattern, and the colour of the hind coxa, which is black in T. rufothorax and orange-brown in T. atriventris . Additionally, the male claspers of T. rufothorax do not have the pronounced ventral angulation found in all individuals of T. atriventris ( Figs 62, 63 ).

Biological notes: Thyreodon rufothorax is a Mesoamerican species that occurs in both Panama and Costa Rica (and possibly further afield, but as it has frequently been confused with T. atriventris , other locality records require verification). In Costa Rica it occurs below about 600 m elevation (and is sympatric over this range with T. atriventris ). This broad geographical range is congruent with the broad range of its known host caterpillars (see below). It comes frequently to lights placed out in the forest, which, coupled with its large size and gaudy colour, is the reason why there are so many individuals in the INBio collections (see below). From this we also deduce that it searches for caterpillars at night (as well as possibly in the daytime). It (and/or T. atriventris ) has been encountered in the daytime visiting the fly- and wasppollinated flowers of Allophylus occidentalis (Sapindaceae) , Forsteronia spicata (Apocynaceae) and Trigonia rugosa (Trigoniaceae) (along with Rhynchophion flammipennis ).

All but one rearing record of Thyreodon rufothorax are from caterpillars of Pachylioides resumens (Sphingidae) [81-SRNP-664; 82-SRNP-598; 89-SRNP-393; 91-SRNP-2439; 99-SRNP-7108; 01-SRNP-14720] ( Janzen & Hallwachs, 2003). These caterpillars were feeding on Forsteronia spicata (Apocynaceae) , a common woody vine in the understorey (saplings) and upper levels of secondary successional dry forest in Sector Santa Rosa of the ACG. Of 229 wild-caught dry forest Pachylioides resumens caterpillars, 5% were attacked by T. rufothorax ( Table 2). However, 3% of these 229 caterpillars were killed by tachinid fly larvae before they reached the prepupal stage, and a few of these caterpillars may therefore have had T. atriventris larvae in them (nothing is known of the competitive abilities of young Thyreodon larvae in the face of co-occupation of a caterpillar by tachinid fly larvae). The single rearing from Pachygonidia drucei is from a total sample of ten larvae ( P. drucei is a very low-density larva wherever it is found), and it was feeding on the rare woody vine Doliocarpus dentatus (Dilleniaceae) in the same dry forest with the Pachylioides resumens caterpillars. The large green caterpillars of P. resumens and P. drucei are superficially very similar in shape, weight and body size (see photographs in Janzen & Hallwachs, 2003). Both caterpillars make a shallow and nearly silk-free pupation chamber in the litter, and T. rufothorax spins its large, hard, tough cocoon in the centre of this chamber. The caterpillars that were parasitized ranged from second to last (fifth) instar when captured.

Not enough Pachylioides resumens and Pachygonidia drucei larvae have been reared from the ACG rain forest (five and five, respectively) to know if it even uses these two caterpillars there, much less at what frequency it might occur. Because more than 15 000 other sphingid larvae of about 65 species have been reared from the ACG dry forest, we feel comfortable in concluding that P. resumens and P. drucei are the sole species attacked by T. rufothorax . Both of these species of caterpillars occur throughout the Costa Rican range of T. rufothorax collected as adults at lights.

T. rufothorax stays in the cocoon for 41–89 days (in one case, 332 days) ( Janzen & Hallwachs, 2003). Lineages that eclose within 1.5–3 months are probably having 2–3 generations during the rainy season, as both species of host caterpillars are among those that have 2–3 consecutive generations during the rainy season (rather than being univoltine or migrating out of the dry forest by the middle of the rainy season). The wasps that remain about 1 year in the cocoon are being univoltine. These generalizations are based on four T. rufothorax that eclosed after parasitizing P. resumens , one that eclosed after parasitizing P. drucei and four more that only survived to the cocoon stage after parasitizing P. resumens (the cocoons of T. rufothorax can be distinguished by being slightly smaller and less angular than are those of T. atriventris ). We have no knowledge of adult survival, but adults are not encountered at light or in Malaise traps during the dry season (a season when there are no dry forest P. resumens or P. drucei caterpillars), and are most common at lights during the early rainy season, when they are presumably eclosing from cocoons spun either at the beginning or the end of the previous rainy season. In short, T. rufothorax has 2–3 generations per 6-month rainy season but some individuals behave in an univoltine manner.

The biology of T. rufothorax is nearly identical to that of T. atriventris , except for the choice of caterpillars to parasitize. Two Cidaphus rostratus ( Ichneumonidae : Mesochorinae ) have been reared as hyperparasites of T. rufothorax [86-SRNP-176.1, 93-SRNP-2308]. The host caterpillars were collected as third instars feeding on Forsteronia spicata . The newly eclosed hyperparasites cut exit holes in the anterior end of the T. rufothorax cocoon 1 or 2 years after spinning. The cocoon was in a dry bottle at ambient temperature inside a non-airconditioned house in the forest. C. rostratus is the only species of hyperparasite entered in the inventory that remains more than 1 year in the cocoon (and see Thyreodon sharkeyi ).

Material examined: Holotype ♀, PANAMA, Bugaba , 260–500 m (Champion) ( BMNH).

Non-type material: COSTA RICA: Alajuela Prov.: 1 ♂, Caño Negro , 20 m, v.1993 (Martinez) ( INBio ); 1 ♀, Monteverde, Estacion Laguna Pocosol, 850 m, vii.1991 (Bello) ( INBio ): Guanacaste Prov.: 2 ♂, Barra Honda National Park, 3 km NW Nacaome, 100 m, vii.1992 (Reyes) ( INBio ); 1 ♀, Guanacaste National Park, Estacion Los Almendros, 300 m, v.1994 (López) ( INBio ); 3 ♀, 3 ♂, Guanacaste National Park, reared as per data above (Janzen & Hallwachs) (JHVC); 1 ♀, 2 ♂, Guanacaste National Park, Estacion Maritza, W slope Volcán Orosi, 560 m, vi, viii.1990 (Blanco) ( INBio ); 3 ♀, 6 ♂, Guanacaste National Park, Estacion Murcielago, 8 km SW Cuajiniquil, 100 m, vi.1994 ( Caño ) ( INBio ); 1 ♀, Guanacaste National Park, Estacion Pitilla, 680 m, iii–iv.1989 (Gauld & Mitchell) (BMNH); 5 ♀, Guanacaste National Park, Estacion Pitilla, 9 km S Santa Cecilia, 700 m, iv.1990, iii–iv.1992, v.1993, iv.1995 (Rios & Moraga) ( INBio ); 6 ♀, 1 ♂, Guanacaste National Park, Finca Jenny, 30 km N Liberia, 240 m, vii.1992, vii.1993 (Araya) ( INBio ); 8 ♀ 5 ♂, Santa Rosa National Park, 300 m, v–vi.1985 (Janzen & Hallwachs) ( INBio ); 4 ♀, 1 ♂, same locality, vi.1989 (Gauld & Mitchell) (BMNH); 3 ♀, 2 ♂, same locality, vi–vii.1990, vi.1992 (Parataxonomists) ( INBio ); 3 ♀, 3 ♂, same locality, reared as per data listed above (Janzen & Hallwachs) (JHVC): Heredia Prov.: 1 ♀, La Virgen del Socorro, 1.5 km SE Cariblanco, 0 m, ii.1997 (Janzen) ( INBio ): Limón Prov.: 1 ♀, 4 ♂, Cerro Cocori, Finca Rojas, 150 m, iv–v.1992, vii.1993, iii.1994 (Rojas) ( INBio ): Puntarenas Prov.: 1 ♂, Estacion Agulas, Sendero Perruja, 300 m, iii.1998 (Azofeifa) ( INBio ); 1 ♂, Finca Cafrosa, 1.7 km E Escuela de Progreso, 1270 m, iii.1996 ( Chinchilla ) ( INBio ); 2 ♂, Finca Cafrosa, Embalce, 800 m NW de Tigra, 1280 m, iii.1996 (Navarro) ( INBio ); 4 ♀, 1 ♂, Carara Biological Reserve, Estacion Quebrada Bonita, 50 m, viii–x.1989 (Gauld) (BMNH); 18 ♀, 5 ♂, same locality, v–vi.1990, v, xi.1992 i.1994 (Parataxonomists) ( INBio ); 1 ♂, Osa Peninsula, Bosque Esquinas, 200 m, iii.1994 ( Segura ) ( INBio ); 1 ♀, Osa Peninsula, Corcovado National Park, Estacion Sirena, 0–100 m, x.1989 (Gauld) (BMNH); 7 ♀, 1 ♂, same locality, i.1990, viii.1991, i, v, xi.1993, iv.1994, iv.1995 (Parataxonomists) ( INBio ); 1 ♀, Osa Peninsula, Estacion Esquinas, 0 m, ii.1993 ( Segura ) ( INBio ); 8 ♀, 13 ♂, Osa Peninsula, Rancho Quemado, 200 m, i, viii, xii.1991, ii–iii, v.1992, xi.1993, v.1994 (Marin & Quesada ) ( INBio ).

Figures

Figures 7–14. Fore wings, showing colour patterns. 7, Rhynchophion flammipennis, normal form. 8, Rhynchophion flammipennis, dark form. 9, Thyreodon rufothorax. 10, T. atriventris. 11. T. maculipennis. 12. T. walkerae. 13. T. zitaniae. 14. T. papei.

Figures 53–63. Apex of metasoma and male genital capsule, lateral; 53, T. maculipennis; 54, T. erythrocera; 55, T. whitfieldi; 56, T. laticinctus; 57, T. zitaniae; 58, T. papei; 59, T. morosus; 60, T. schauffi; 61, T. darlingi; 62, T. rufothorax; 63, T. atriventris.