Cresson Pate, 1938

Packer, Laurence, 2021, A Revision of Cresson Pate (Hymenoptera, Apoidea, Bembicidae) with the description of two new species, Journal of Hymenoptera Research 85, pp. 81-117 : 81

Cresson Pate, 1938

Cressonius Bradley, 1956: 257. Unnecessary emendation.

Type species.

Nysson parvispinosus Reed, 1894: 641, by original designation and monotypy.

Diagnosis.

Cresson can be separated from other South American nyssonine wasps by the combination of i) metatibia lacking teeth, with bristles that clearly arise from an articulation in a socket; ii) metasomal sterna lacking lateral lobes as opposed to lobes present (compare Fig. 5 herein with fig. 154 in Bohart and Menke 1976); iii) metasomal terga with posterior margins thickened and appearing double-edged (Fig. 4 , yellow curly bracket) versus simple and iv) a Υ-shaped crest on the lower frontal area with the apices of the paired arms recurved (Figs 1-3 ). Feature i) separates Cresson from Idionysson Pate, 1940, Metanysson Ashmead, 1899, Neonysson Bohart, 1968, and Zanysson Rohwer, 1914, ii) separates it from both Antomartinezius and Perisson , iii) separates it from Losada Pate, 1940 and Nysson and iv) from Epinysson Pate, 1935, Foxia Ashmead, 1898 and all aforementioned genera except Antomartinezius and Perisson .

Description.

Colouration: Black with white to cream coloured markings on face, pronotal collar (rarely absent), pronotal lobe, scutellum (rarely absent), legs, subapical bands on most terga, sometimes on sterna; red markings on metasoma absent to extensive. Both sexes with labrum and base of mandible pale, female with clypeus pale laterally, black medially, male clypeus entirely pale except lip orange-brown.

Pubescence: Silvery appressed to subappressed setae extensive on face, genal area, dorsal surface of pronotum, most of mesopleuron (sparser anteriorly and ventrally, absent posteriorly), posterolaterally on scutellum, metanotum, dorsolateral area of propodeum and sometimes on T1, setae of scutellum and metanotum anteriorly or anterolaterally oriented; fine erect setae longer on upper part of face, shorter on mesoscutum and mesopleuron, vertically oriented dense row of short setae occupying space between extreme apical margin of terga and base of succeeding tergum, metasomal sterna with scattered longer erect setae; male with median setal fringes on S2-S5 situated in a gap in the apical sternal depressions, lateralmost fringe setae longest, posteromedially oriented but sparser than more posteriorly oriented remaining fringe setae.

Surface sculpture: Microsculpture largely absent, integument shiny, punctures bimodal in size on face and mesoscutum, minute punctures sparsely scattered among interspaces between larger mostly dense punctures; larger punctures especially on face and mesoscutum with minute punctures at their bottoms and often with several punctures aggregated in groups with edges raised, sometimes giving somewhat striate appearance; minute punctures more numerous on metasomal terga and sterna among distinct larger punctures; junctions between mesoscutum and scutellum and between meso- and metapleuron foveate, the latter finely so; lateral surface of pronotum and posterodorsal part of lateral surface of propodeum obliquely costate; posterior portion of mesopleuron, metapleuron and rest of lateral surface of propodeum generally lacking sculpture, glassy smooth; posterior surface of propodeum coarsely sculptured; metapostnotum rugoso-striate dorsally. Portion of metasomal terga posterior to graduli (usually hidden beneath preceding tergum) imbricate, dull; sterna with similar imbricate areas more extensive. Metasomal terga and sterna with most punctures separated by distance greater than their diameters, except last metasomal tergum with coarse, irregularly shaped, almost crowded punctures; last visible sternum with small, scattered punctures; apical impressed tergal and sternal depressions with row of punctures at their base.

Structure: Head 1.3-1.5 × wider than long; labrum short, transverse, apical margin slightly concave to transverse medially; clypeus short, apicomedially concave with pronounced bevelled edge, lip approximately half as wide as clypeus; supraclypeal area small, sometimes hidden beneath ventral expansion of frontal crest, crest Ϋ-shaped, ventral margin of crest swollen with angulate ventral incision, in frontal view crest obscures the medial margin of the antennal socket lateroventrally, medially the crest is conspicuously developed, almost lamellate, dorsal arms less developed, recurved, space between median lamella and entire recurved arm with one dorsolaterally oriented lamella and varying number of subparallel carinae; space between lateral margin of supra-antennal area and compound eye with frontal depression extending upwards for a variable distance below lower tangent of median ocellus, dorsal margin of depression often ill defined; inner margin of compound eyes markedly convergent below, shortest distance between them at base of clypeus; occipital and hypostomal carinae complete, lamellate. Scape longer than wide, slightly produced basoventrally, integument somewhat translucent for apicoventral one-third of length; pedicel with medial surface globose, conspicuously narrowed towards base, lateral surface straighter; male apical flagellomere falcate, concave below narrowing to acute apex. Pronotum with vertical carina that in dorsal view appears as a tooth, pronotal collar in dorsal view transverse anteromedially, convex anterolaterally; in profile gradually rounded onto anterior declivitous surface except abruptly and angulately so medially. Mesoscutum posterolaterally markedly reflexed upward, projecting over medial margin of tegula. Lateral propodeal spine conspicuous, acute. Mesotibia of male with one apical spine, mesobasitarsus of male with ventral setal fringe; female lacking rake spines on protarsus; metatibia slightly concave apicodorsally, extreme apex angulate dorsally, lacking robust spines or teeth; arolia in both sexes small. Three submarginal cells, second cell petiolate; stigma subequal in size to prestigma; hindwing media diverging beyond cu-a by more than twice the length of the latter; jugal lobe somewhat larger than tegula. Metasomal terga posterior margins double-edged. T2 transversely depressed anteriorly. Apical tergum of both sexes with apicolateral margin spinose; in females, the medial pair longer than others, in males the single median spine is short. S2 swollen anteromedially and depressed anterolaterally. Metasomal sterna not extended laterally as lobes, male S2-S5 with apical sternal depression abruptly absent medially, this area in female sometimes slightly concave.

Figures

Figure 4. Apex of T 1 and base of T 2 of female C. parvispinosus to show measurement of puncture spacing (diameter (d) - blue line, interspace length (i) red line (here i ~ 2 d as indicated to the bottom right) and the double-edged nature of the apex of the tergum, indicated by the yellow curly bracket. Scale bar: 100 µm.

Figure 5. Oblique ventral view of metasoma of male C. parvispinosus to show apicomedial setal fringes situated within the medial gap in apical sternal depressions along with the angles formed at the margin of the gap (inset). The angle formed by the red and blue lines indicates the anterior angle, that formed by the blue and yellow lines the posterior angle. Scale bar: 0.5 mm.

Figures 1 - 3. Supra-antennal areas of C. parvispinosus 1 standard light photomicrograph of male, red line indicates measurement of length of the area, the blue line indicates its width. Scale bar: 0.5 mm. 2 ESEM of female, the white arrow indicates the lamella. Scale bar: 300 µm. 3 ESEM of another female showing different number of carinae to that in figure 2. Scale bar: 200 µm.