Argogorytes caerulescens (R. Turner 1914)

Argogorytes caerulescens (Turner)

Gorytes caerulescens Turner, 1914:251 [; Kandy, Ceylon; type in British Museum (Natural History)].—Maidl and Klima, 1939:55 [listed].

Argogorytes caerulescens (Turner).—Bohart and Menke, 1976:492 [listed].

This rare species is known from only two females, the type from Kandy, presumably Udawattakele Sanctuary, and a specimen from Weddagala in the Sinharaja Jungle. These localities are at altitudes of 100–640 m, and have an average annual rainfall of 1950–3900 mm. Argogorytes caerulescens is distinguished from its congeners as well as the other Ceylonese nyssonids by the metallic blue integument.

The genus Argogorytes is a diverse group, and I suspect that eventually the species may be allocated to two or more genera or subgenera. A primary division in the genus may be into a group of relatively few species having a narrow pygidium with few setae in the female and a larger group with a broad triangular pygidium densely clothed with decumbent setae (Figures 13, 14). These pygidial characters are similar to those in the crabronid genus Lestica, in which females of the subgenus Solenius have the narrow pygidium whereas in typical Lestica the female pygidium is broad and triangular. Some species of Solenius are known to nest in sound or rotten wood, while several of typical Lestica nest in the soil. I surmise that similar biological characters may separate these two groups of species in Argogorytes. Females of the group with a broad pygidium nest in the soil (Callan, 1980), but the nesting habits of those with a narrow pygidium are unknown.

Argogorytes caerulescens is unique in the genus in that it has a more robust form, the pronotal collar is elevated anteriorly into a narrow lamella, the forewing costa is not curved outward near base, and abdominal terga II–IV have a narrow, reflexed, apical lamella (Figure 10). Other unusual features, which, however, are found in a few other Argogorytes, are the presence of an apical spur on the outer surface of the fore- and midtibiae, plantulae present on tarsal segments I–IV, abdominal terga II–IV without an apical fringe of dense short setae, and the narrow, subparallel-sided, female pygidium.

FEMALE.—Length 11–12 mm. Body form more robust than in other Argogorytes; head, thorax, and abdomen metallic blue, antenna and legs black. Wings infumated, forewing more strongly so, stigma black, veins dark brown. Vestiture short, silvery, erect and denser on head, sparser on thorax, somewhat denser on abdomen, rather abundant, dense silvery pile on median and posterior parts of second abdominal sternum, and posterolaterally on sterna III–V.

Head height from apex of clypeus to occiput 0.9 times width; eyes slightly diverging above, inner margin slightly emarginate halfway between antennal insertions and anterior ocellus; interocular distance at base of clypeus 0.95 times that at anterior ocellus; clypeus twice as wide as high, apical margin in middle shallowly incurved, surface with scattered large punctures interspersed among dense small punctures; lower half of front with contiguous small punctures and a weak median carina, upper half with somewhat larger punctures, many of them separated by half the diameter of a puncture; vertex punctation similar to that on upper front; temples with rather dense small punctures.

Pronotal collar with an anterior, transverse, low, erect lamella; scutum anterolaterally with contiguous small punctures, elsewhere with large contiguous punctures or pits; scutellum in middle with a narrow, transverse, raised smooth area, posteriorly with a small circular pubescent pit, elsewhere with contiguous punctures a bit smaller than those on scutum; metanotum similarly punctate, slightly raised in middle; mesopleuron adjacent to pronotal lobe coarsely, closely pitted, remainder with strong, close, oblique to longitudinal ridges with fine, interspersed, minute, piliferous punctures; metapleuron smooth with moderately dense, fine, piliferous punctures; triangular propodeal enclosure with coarse, slightly irregular longitudinal rugae margined laterally by short oblique rugae, the rest of dorsal area with longer oblique rugae; posterior propodeal surface with rugulae radiating outward and upward from abdominal insertion; lateral propodeal surface mostly smooth but with a curved posterolateral ruga; fore- and midtibiae with an apical spur on outer surface; plantulae present on tarsal segments I–IV.

Abdominal terga I–III with small punctures mostly separated by 0.5–1.0 times the diameter of a puncture, tergum IV with smaller, similarly spaced punctures except a narrow anterior strip closely punctate, tergum V with fine, moderately dense punctures; terga II–IV with a narrow reflexed lamella at apex (Figure 10); pygidium (Figure 14) narrow, moderately short, sub-parallelsided, with a rounded median ridge and a lateral groove bearing a few setiferous punctures; first sternum with a strong complete median keel; sternum II raised into a median rounded prominence about a third from base.

MALE.—Unknown.

SPECIMENS EXAMINED.—CENTRAL PROVINCE, Kandy District: 1, Kandy, Nov, O.S. Wickwar (type; London).

SABARAGAMUWA PROVINCE, Ratnapura District: 1, Sinharaja Forest, Weddagala, 18–21 Jun, Krombein et al. (USNM).

There is only one species in Sri Lanka, the rarely collected endemic Lestiphorus greenii (Bingham). Another species occurs in India and may be collected ultimately in Sri Lanka.