Brachystegus basalis (F. Smith 1856)

Brachystegus basalis (Smith)

Nysson basalis Smith, 1856:355 (, India; type in Hope Department of Entomology, Oxford University).—Gerstaecker, 1867:112 [listed].—Handlirsch, 1887:401 [translation into German of original description].—Bingham, 1897:269, 270 [quotation of original description].—Dalla Torre, 1897:567 [listed].—Turner, 1914:254, 255 [, ; South and West India].—Maidl and Klima, 1939;134 [listed].—Bohart and Menke, 1976:469 [listed].

Smith's unique male type is indubitably a Brachystegus, not a Nysson, for it possesses the apical fringes of dense, long, curled setae on sterna II–V and the irregularly serrate outer surface of the hind tibia that characterize the former genus but are lacking in Nysson. The type is on a short pin bearing a small rectangular label that is blank on the upper surface and bears a scrawled “Ind.” on the lower. It is 9.1 mm long and agrees well with most of the specimens examined.

The rarely collected B. basalis occurs in Sri Lanka at low altitudes from near sea level to about 150 m. We collected only two females and a male, and I have seen one other male from Sri Lanka. I have also examined two females and seven males from India including the type. Typically the pale markings are ivory but they are pale yellow in a male from Tranquebar, South India, and bright yellow in a male from Colombo, Sri Lanka. Also two males from Moyar Camp, Nilgiri Hills and Coimbatore, both South India, have light red rather than dark femora and tibiae.

FEMALE.—Length 7.0–9.1 mm. Black, the following ivory: small round spot behind and laterad of posterior ocellus and transverse oval posterolateral spots on terga I–IV, those on I large, on II slightly smaller, and III–IV quite small; mandible reddish except basally and at tip, and occasionally anterior tibia beneath and middle tibia entirely. Vestiture appressed, silvery, quite dense on lower part of front, temple, pronotal dorsum, mesopleuron and -sternum, coxae and femora beneath, upper half of declivous surface of tergum I, sternum II, and particularly dense on clypeus and dorsal propodeal surface laterad of enclosure. Wings slightly infumated except marginal cell and apex of forewing more strongly so; stigma and veins brown.

Eyes diverging above, interocular distance at base of clypeus 0.6 times that at anterior ocellus; clypeal apex bare, thickened, bidentate in middle; frontal carina stronger than in B. dubitatus, extending 0.4 times distance to anterior ocellus; upper front with large, mostly contiguous pits bearing many micropunctures from which tomentum arises (Figure 8), interspaces between pits not micropunctate.

Pronotal dorsum weakly ridged; scutum, scutellum and mesopleuron contiguously pitted, the pits larger than on front and in B. dubitatus; propodeal enclosure dorsally with a few longitudinal rugae, posteriorly irregularly rugose; posterolateral propodeal tooth moderately developed, somewhat stouter than in B. dubitatus; posterior propodeal surface with a few longitudinal rugulae in middle that enclose weak small rugulose reticulations, laterad of which are a few rugulae radiating outward and upward from abdominal insertion and enclosing larger, weak, rugulose reticulations.

Disk of tergum I with moderately large subcontiguous punctures that become more separated laterally, interspaces with small punctures; terga II–IV with more scattered, larger punctures except posteriorly, and with abundant small punctures in interspaces between large ones; tergum V with subcontiguous, moderately large punctures; pygidium convex but not so strongly as in B. dubitatus, closely and moderately punctate, apex rounded, distance between lateral carinae at base 0.7 times length of pygidium; sternum II gently convex toward base.

MALE.—Length 7.1–9.2 mm. Color and vestiture as in female except tergum V frequently with small posterolateral spot (present in type), pale markings pale or bright yellow in two of eight specimens, and femora and tibiae light red in two.

Sculpture as in female except as follows: last flagellar segment enlarged, concave beneath and more strongly so than in B. dubitatus; tergum VI posteriorly with a lateral carina that terminates in a backwardly directed tooth; apical margin of tergum VII narrowly rounded out between lateral teeth so that apex appears tridentate.

SPECIMENS EXAMINED.—EASTERN PROVINCE, Trincomalee District: 1, 1, Trincomalee, China Bay, 0–30 m, 8–11 Oct, Krombein et al. (USNM).

WESTERN PROVINCE, Colombo District: 1, Colombo, Mar, Wickwar (Colombo); 1, Labugama Reservoir Jungle, 2–4 Feb, Krombein et al. (USNM).

INDIA. 1, no other data (Oxford; Smith's type); 1, Quetta, Aug (London); 1, Coimbatore, on bush, Fletcher (London); 1, Nasik, Bombay Presidency (London); 2, Coimbatore, South India, Aug, Sep, Nathan (USNM, Corvallis); 1, Moyar Camp, Nilgiri Hills, South India, 2900 ft (885 m), May, Nathan (Corvallis); 1, Tranquebar, South India, Feb, Nathan (Corvallis).

Only four of the 31 genera recognized by Bohart and Menke (1976:481–523) are known to occur in Sri Lanka, Argogorytes Ashmead, Lestiphorus Lepeletier, Ammatomus Costa and Hoplisoides Gribodo. I have seen specimens of an apparently undescribed species of Dienoplus Fox from central and southern India, so that taxon may be found ultimately in Sri Lanka.

One decidedly anomalous species, Argogorytes caerulescens (Turner) is endemic in Sri Lanka. I have seen an undescribed species from India that may be found eventually in Sri Lanka.