Pison nigellum Krombein

Pulawski, Wojciech J., 2018, A Revision of the Wasp Genus Pison Jurine, 1808 of Australia and New Zealand, New Guinea, and the Pacific Islands (Hymenoptera: Crabronidae), Proceedings of the California Academy of Sciences 65, pp. 1-584 : 543-546

Pison nigellum Krombein

Figures 1320-1329.

Pison nigellum Krombein, 1949b:401 , ♀, ♂. Holotype: ♀, Caroline Islands: Pohnpei Island (formerly Ponape): Kolonia (USNM), paratypes examined. – Krombein, 1949b:384 (in key to Sphecidae of Micronesia), 1950b:139 (nesting in cliffs); Yasumatsu, 1953:134 (in list of Pison of Pacific islands), 144 (bibliographic references; Caroline Islands); R. Bohart and Menke, 1976:336 (in checklist of world Sphecidae ); Gess, 1981:70 (nesting in pre-existing cavities reported).

RECOGNITION.– Pison esakii and P. nigellum are the only Pacific Islands species with black setae on the upper frons, thorax, and propodeum. Subsidiary recognition features are: punctures several diameters apart on frons, several diameters apart on scutal disk and propodeal dorsum, setae of lower gena sinuous, up to about 1.5 × midocellar diameter long and appressed on tergum I, ocellocular distance about 0.3 × hindocellar diameter, and gastral terga without silvery, apical fasciae. Unlike P. esakii , the propodeum of P. nigellum lacks the longitudinal carina separating the dorsum from the side (carina present in P. esakii ), the median sulcus and carina on the dorsum are inconspicuous (well defined in P. esakii ), and the propodeal posterior surface is unridged in dorsal half (conspicuously ridged throughout in P. esakii ).The two species have different geographic distributions: P. esakii is known from Guam and the adjacend island of Rota, whereas P. nigellum occurs on the island of Pohnpei.

DESCRIPTION.– Frons dull, finely punctate, punctures several diameters apart (Fig. 1322). Occipital carina slightly expanded ventrally (carina width about 0.2 × midocellar diameter). Posterior mandibular margin slightly emarginate (Fig. 1324). Gena narrow in dorsal view (Fig. 1323). Labrum emarginate. Anteromedian pronotal pit transversely elongate, about as long as midocellar diameter. Propleuron sparsely punctate anteriorly. Scutum either foveate or not foveate along flange, with short longitudinal ridges adjacent to posterior margin; scutal punctures fine, several diameters apart (about 1-2 diameters apart next to foremargin); interspaces aciculate. Tegula not enlarged. Mesopleural punctures several diameters apart; interspaces aciculate. Postspiracular carina present, about 1.5 × as long as midocellar diameter; integument depressed between postspiracular carina and episternal sulcus. Metapleural sulcus not costulate between dorsal and ventral metapleural pits. Propodeum without longitudinal carina separating side from dorsum and posterior surface; dorsum and side unridged, minutely punctate, punctures several diameters apart); dorsum in female with inconspicuous middle carina in shallow sulcus (Fig. 1325), carina in some specimens exending only to dorsum midlength, without sulcus in male; posterior surface microscopically punctate (punctures several diameters apart), unridged in dorsal half, in ventral half with shallow concavity on each side of median sulcus (concavity ridged, but ridges visible only from certain angles). Posteroventral forefemoral surface finely punctate, punctures 2-4 diameters apart. Hindcoxal dorsum with outer margin sharply carinate. Horizontal part of tergum I, tergum II, and sternum II with microscopic punctures that are many diameters apart, interspaces mesally unsculptured, shiny.

Setae black on the head, thorax, and propodeum except silvery on lower frons laterally and on clypeus laterally, erect on upper frons and scutum (here varying in length from about 0.5 × to about 0.8 × midocellar diameter), not concealing integument on clypeus; setae of lower gena sinuous, up to about 1.5 × midocellar diameter in length; terga I and II glabrous mesally. Terga without setal, silvery fasciae.

Body all black.

♀.– Upper interocular distance equal to 0.48-0.52 × lower interocular distance; ocellocular distance equal to 0.2 × hindocellar diameter, distance between hindocelli equal to 0.5-0.6 × hindocellar diameter; eye height equal to 1.06 × distance between eye notches. Free margin of clypeal lamella roundly arcuate to slightly sinuous (Fig. 1320). Dorsal length of flagellomere I 2.5-2.6 × apical width, of flagellomere IX 2.1-2.2 × apical width. Mandible: trimmal carina with small incision at about midlength. Length 7.5-8.0 mm; head width 2.1-2.3 mm.

♂.– Upper interocular distance equal to 0.66 × lower interocular distance; ocellocular distance equal to 0.3 × hindocellar diameter, distance between hindocelli equal to 0.6 × hindocellar diameter; eye height equal to 1.10 × distance between eye notches. Free margin of clypeal lamella arcuate, with rounded midpoint (Fig. 1321). Dorsal length of flagellomere I 2.4 × apical width, of flagellomere X 1.2 × apical width. Mandible with abductor ridge. Sternum VIII truncate apically (minimally concave), without apicolateral corner (Fig. 1326). Genitalia: Figs. 1327, 1328. Length 6.8 mm; head width 1.9 mm.

NESTING HABITS.– Krombein (1950) reported that the species was nesting in a clay bank, probably using abandoned burrows of other insects.

GEOGRAPHIC DISTRIBUTION (Fig. 1329).– Known only from island of Pohnpei (formerly Ponape) in the Caroline Archipelago.

RECORDS (all specimens examined except those from Mount Tamatamansakir and except the allotype male are paratypes of Pison nigellum ).– FEDERATED STATES OF MICRONESIA: Pohnpei Island: Kolonia (1 ♀, BISH; 1 ♀, USNM), Mount Tamatamansakir (4 ♀, BISH) , Roi (1 ♀, BISH; 2 ♀, USNM), Reitao (1 ♀, BISH) , Ronkiti (2 ♀, BISH; 1 ♀, CAS; 2 ♀, USNM), Tamon-Reitao (1 ♀, BISH; 1 ♀, USNM), Wonel (1 ♀, BISH) , no specific locality (3 ♀, 1 ♂, BISH; 1 ♀, CAS; 3 ♀, USNM) .