Thyreodon santarosae, PORTER, 1986

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 : 317-319

3. THYREODON SANTAROSAE PORTER

Thyreodon santarosae Porter, 1986: 133 . Holotype ♂, COSTA RICA (USNM) [examined].

Fore wing length 17.2–21.8 mm; clypeus convex, with apex pointed medially; malar space 0.4–0.5 times basal mandibular width; maxillary palp long with second palpomere strongly broadened and flattened; lower face centrally coarsely punctate; frons with a raised quadrate prominence between antennal sockets and with a high, rather blunt carina extending from outer rim of antennal sockets upwards, close to and parallel with eye margin; frons centrally rugose, but with the impressions above the antennal sockets transversely striate; ocelli small, the lateral ocellus separated from eye by about 1.3 times its own maximum diameter; head in dorsal view with gena rather evenly rounded behind eye, occipital carina strong, its lower end not reaching hypostomal carina; antenna setaceous, with 62–64 flagellomeres, the 20th transverse, 0.6–0.7 times as long as broad, the subapical ones with setae which are shorter than the diameter of the flagellomere. Pronotum short with anterior margin thickened and weakly reflexed, and with posterior margin centrally quadrately swollen, forming an angular projecting ridge which is separated from the anterior margin by a deep U-shaped groove; epomia absent; propleuron sparsely punctate, with lower corner rounded, peripherally with a few coarse punctures above lower corner; mesoscutum moderately coarsely punctate, with broad, very shallow, reticulated notauli that are confluent posteriorly, inner anterior margin of notaulus unspecialized; scutoscutellar groove deep but short, laterally margined by raised, simple carinae; scutellum punctate, broad and convex; mesopleuron moderately closely and quite coarsely punctate, without a sternaular impression; metapleuron finely punctate with a few obscure diagonal ridges; propodeum slightly globose, laterally not flattened, punctate, without a ridge above and behind the spiracle; propodeum posterodorsally smooth with scattered punctures, centrally with a single shallow longitudinal impression. Fore leg of female rather stout, with coxa with a low, bluntly rounded protuberance behind trochanteral insertion, with 5th tarsomere 1.2–1.3 times as long as preceding two tarsomeres, with tarsal claw long and with fine, close pectinae; hind coxa in profile moderately small, its hind end more or less level with hind end of propodeum; hind femur slender, about 5 times as long as maximally deep; hind tarsus of male with moderately short, dense 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 moderately slender, anteriorly slightly laterally compressed; tergite II, in lateral view, 1.5–1.6 times as long as posteriorly deep. Male with subgenital plate small and convex, covered with fine hair; claspers quite long, the dorsal apex obliquely truncate, the lower margin rounded before apex, and with a very shallow, broad dorsal notch; aedeagus on profile with apex up-turned, weakly inflated, rounded.

Generally a dark brownish black species with distal parts of legs yellowish brown; wings yellowish brown with periphery blackish infumate. Males always with lower face bright yellow, sometimes with genae and fore and mid legs yellow-marked too, and with most of body reddish brown.

Remarks: Thyreodon santarosae is immediately recognizable by the rather globose, polished and punctate propodeum ( Fig. 33 ), which is quite unlike that of any other Central American Thyreodon , although it is similar to the South American species T. marginipennis (Brullé) . Both species also have a raised quadrate prominence between their antennal sockets ( Fig. 15 ), quite unlike the frons of other species, and have the scutellum rather broad posteriorly. T. santarosae differs from T. marginipennis in that the carinae flanking the scuto-scutellar groove are simple, rather than strongly anteriorly flattened. The propodeum of T. marginipennis bears sparse rugae centrally and anteriorly, although it is otherwise rather like that of T. santarosae .

Biological notes: Thyreodon santarosae is only known to occur in the drier areas of north-western Costa Rica. Only four individuals have been wild-collected but 26 individuals have been reared [84-SRNP-948a; 84-SRNP-1116; 84-SRNP-1124; 84-SRNP-1207; 84-SRNP-1263.1; 84-SRNP-1267; 89-SRNP-283; 91-SRNP-1160; 93-SRNP-2673; 94-SRNP-3669; 95-SRNP-7645; 95-SRNP-10554; 96-SRNP-5780; 96-SRNP-7438; 96-SRNP-7439; 96-SRNP-7448; 96-SRNP-7458; 96-SRNP-7460; 96-SRNP-7465; 96-SRNP-7484; 96-SRNP-7488; 96-SRNP-7815;

96-SRNP-10019; 98-SRNP-12089; 98-SRNP-12187.01; 98-SRNP-12274] ( Janzen & Hallwachs, 2003). This wasp ( Porter, 1986) has evolutionarily left behind the Sphingidae and moved on to the large and naked scolibearing (not hairy, not urticating) caterpillars of ceratocampine Saturniidae ( Gauld, 1988; Janzen & Gauld, 1997). They are superficially sphingid-like in aspect. This is the only species of Thyreodon known to have moved on to Saturniidae (though the structurally similar T. marginipennis is an obvious additional candidate; to date the biology of this species is unknown). T. santarosae has been reared from all seven species of the medium-sized ACG dry forest Ceratocampinae ( Othorene purpurascens , Othorene verana , Ptiloscola dargei , Syssphinx quadrilineata , Syssphinx mexicana , Syssphinx molina , Syssphinx colla ). It probably does not parasitize the three very large ceratocampine saturniids Citheronia and Eacles that occur in this habitat, given that 443 of them have been reared without encountering this wasp. The small larva of Adeloneiva isara, the single remaining ACG dry forest ceratocampine, may be too small to be an adequate host (32 rearing records, Janzen & Hallwachs, 2003). T. santarosae is most easily reared by collecting a large batch of last instar caterpillars of S. molina from the crowns of large Pithecellobium saman trees. The host caterpillars feed on a variety of species of trees, shrubs and vines in the Fabaceae (Janzen, 2003) , except that O. verana feeds in the crowns of large oak trees ( Quercus oleioides , Fagaceae ) and O. purpurascens feeds in the crowns of large Manilkara chicle (Sapotaceae) trees. All of these caterpillars pupate in a depression at the interface of the litter and soil, and the T. santarosae cocoons are spun in these depressions. Adult T. santarosae search for caterpillars in full daylight, running clumsily over the foliage in the crowns of large trees. Despite its obvious abundance in the ACG dry forest, this wasp has never been caught in 12 trap years of Malaise traps placed in the understorey and on forest edges.

This wasp may eclose any time between May and October (during the first two-thirds of the rainy season). Some pupae are dormant for a full year, from June–August through to the following May–June, and are therefore effectively univoltine. Others eclose after only 34–54 days, whereas others remain dormant for 60–100 days. The result is that there can be ovipositing adults in the habitat throughout May–October. During this time there are generally some ceratocampine caterpillars present (especially those of Syssphinx molina ), though the largest numbers are available in June–July ( Janzen, 1993).

Material examined: Holotype ♂, COSTA RICA, Guanacaste Prov.: Santa Rosa National Park , 300 m (Janzen & Hallwachs) ( USNM).

Non-type material: COSTA RICA: Guanacaste Prov.: 2 ♂, Guanacaste National Park, Finca Jenny, 31 km N Liberia, 240 m, xi.1988, vi.1994 (Araya) ( INBio ); 14 ♀, 12 ♂, Guanacaste National Park, reared as per data listed above (Janzen & Hallwachs) (JHVC); 1 ♀, Rincon de la Vieja National Park, Estacion Las Pailas, 800 m, viii–ix.1993 (Rodriguez & Sihezar) ( INBio ): Puntarenas Prov.: 1 ♀, Carara Biological Reserve, Estacion Quebrada Bonita, 50 m, vi.1990 ( Zuñiga ) ( INBio ).

Figures

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.

Figures 15–20. SEM photographs of Thyreodon spp. 15–16, head, anterior, showing interantennal area; 15, T. santarosae; 16, T. walkerae. 17–18, mesopleuron, lateral; 17, T. morosus; 18, T. walkerae. 19–20, propodeum, lateral; 19, T. whitfieldi; 20, T. laticinctus.