Jethsura pyriformis

Jethsura pyriformis (Provancher)

Figs 5–6, 11

Ischnus pyriformis Provancher, 1875: 109. Lectotype: ♀ [University of Laval Entomology Collection, Quebec, Canada]: Designated by Gahan & Rohwer (1917). Not examined.

Jethsura ferruginea Cameron, 1902: 374. Holotype: ♀ [Natural History Museum, London, UK]: Synonymized by Townes (1961). Not examined.

Diagnosis. Among Jethsura species, J. pyriformis is immediately recognizable by the overall brownish-red color, whereas at least the head and mesosoma are black in other species. Jethsura pyriformis shares a striking superficial resemblance to an undescribed Stenodontus species that it co-occurs with in southeastern Arizona. Jethsura pyriformis can be differentiated from this undescribed Stenodontus by the anterior constriction of T6 and the shorter first flagellomere in females, and the bidentate mandible with a highly reduced ventral tooth in both sexes. In Stenodontus, the mandible is always unidentate without a trace of a ventral tooth.

Description. Female (Fig. 5A–H). Body length: 8.0– 9.9 mm; fore wing length: 4.4–5.3 mm.

Color. Overall brownish-red with highly variable yellowish marks on mesosoma and black along mesosomal sclerite margins. Head brownish-red, except for dark red mandibular apex, medial paraocular area varying from yellowish to brownish-red and supra-antennal area infrequently (5% of specimens) dark brown to black medially. Antenna: scape and pedicel brownish-red; F1/2 usually anteriorly brownish-red and brown posteriorly, infrequently entirely black; F2/3–F6/8 black; F7/8–12/13 yellow-white to yellow; F13/14–28/29 black. Mesosoma brownish-red, except the following areas yellowish to varying degrees: anterior margin of pronotum with yellowish color stronger anteriorly, posterodorsal corner of pronotum, subalar ridge, and scutellum; approximately 10% of specimens with these areas entirely brownish-red. Legs brownish-red, except for approximately 20% of specimens with fore and middle coxae yellowish anteriorly and tarsomere 5 of fore, middle and hind legs dark brown. Metasoma brownishred. Wing: membrane clear; basal 0.1–0.2 of wing with veins white, remaining sections brown.

Head. Head subquadrate. Mandible moderately wide (MI: ~3.0×). Clypeus smooth and coarsely punctate with punctures separated by 0.5–1.0× their diameter. Supraclypeal area densely, coarsely punctate with punctures separated by 0.2–0.5× their diameter laterally, sparser and finer medially. Gena smooth and finely punctate with punctures separated by 1.5–3.0× their diameter, denser posteriorly. Supra-antennal area smooth and densely, finely punctate with punctures separated by 0.2–0.8× their diameter. Vertex smooth and finely densely punctate medially becoming sparse laterally. Hypostomal and occipital carinae meeting at or slightly before mandibular base. Antenna with 28–29 flagellomeres.

Mesosoma. Of normal width, not laterally flattened. Dorsal 0.5 of pronotum smooth and densely punctate at margins, ventral 0.5 rugulose-punctate. Propleuron smooth and finely, densely punctate with punctures subadjacent. Mesonotum smooth, anterior 0.3 finely, densely punctate becoming denser and indistinct anteriorly, remainder densely punctate with punctures separated by 0.2–1.0× their diameter. Scutellum smooth and moderately punctate with punctures separated by 0.8–1.5× their diameter. Mesopleuron densely punctate with punctures adjacent to subadjacent, some confluent forming transverse rugulae, sparser on speculum. Ventral division of metapleuron densely punctate with punctures adjacent to subadjacent. Propodeum: of normal width, slightly wider than long; weakly rounded mediolaterally; dorsal face densely punctate to partially rugulose-punctate laterally becoming smooth or coriaceous anteromedially; posterior face densely rugulose-punctate; pleural carina well-developed, remainder obsolete to subobsolete except for median longitudinal carina well-developed posteriorly and posterior transverse carina well-developed laterally. Legs of normal length. Hind femur normal, not anteroposteriorly flattened.

Metasoma. MS1 smooth and varying from sparsely punctate to moderately punctate, usually with postpetiole sparser. T2 smooth and densely punctate with punctures separated by 0.5–1.0× their diameter, posterior margin impunctate. T3–7 densely punctate, except for impunctate posterior margins and becoming smoother at posterior tergites. Gastrocoelus varying from shallow to well-developed. Thyridium subobsolete; narrow, 0.4–0.5× as wide as interthyridial width; distant from T2 anterior margin by 0.2–0.3× tergite length.

Male (Fig. 6A–C). Body length: 7.3–9.6 mm; fore wing length: 4.6–5.9 mm. As in female, except for: head yellow with supra-antennal area black medially, gena varying from yellow with posterior margin reddish-brown to nearly entirely reddish-brown, and occiput black; yellowish-white markings on mesosoma much more extensive with the entirety of ventral and dorsal margins of pronotum, subalar ridge, and tegula yellowish-white; propleuron and anterior 0.2 of mesopleuron usually yellowish-white and propodeum usually with posterior submedial yellowish-white marks; black areas around mesosomal sutures more extensive and pronotum medially black; head wider than in female; clypeus narrower than female.

Material examined. Non-type material : See supplementary file.

Distribution. Widely dispersed in the Nearctic region from Newfoundland, Canada to Saltillo, Mexico and from the eastern seaboard to central Colorado and southeastern Arizona (Fig. 11).

The presence of J. pyriformis in the Palearctic should be considered with caution. Two specimens identified by Erich Diller were reported from Hirvensalmi and Tuusula, Finland by Ranin (1982). Only the former specimen could be found at the Finnish Museum of Natural History (J. Paukkunen pers. comm.) and its identity as J. pyriformis was confirmed via examination of the specimen images. Given the occurrence of J. pyriformis as far north as Newfoundland, Canada, it is plausible that it may occur in Finland, although the lack of further specimens (E. Diller pers. comm.) collected in recent decades may indicate that the Finnish specimens were part of an adventive population that has since been extirpated.

Comments. Jethsura pyriformis exhibits considerable chromatic variation in both males and females but particularly in the former. In males, the black areas along the mesosomal sutures and the yellowish-white markings are especially variable. The extent of these black and yellowish-white markings is negatively correlated. For instance, one exceptional male has a predominantly black mesosoma with the typical yellowish-white markings replaced by brownish-red markings. More frequently, males are overall lighter in color with yellowish-white markings more extensive and occasionally with yellowish-white marks appearing in irregular places like the third lateral area of the propodeum. Despite the range of J. pyriformis spanning over 25 degrees of latitude, no geographic signal in either color or size was observed.