Peristenus howardi Shaw

Goulet, Henri & Mason, Peter G., 2006, Review of the Nearctic species of Leiophron and Peristenus (Hymenoptera Braconidae: Euphorinae) parasitizing Lygus (Hemiptera: Miridae: Mirini:), Zootaxa 1323 (1), pp. 1-118 : 60-62

Peristenus howardi Shaw

( Figs. 59, 60 , Table 17)

Peristenus howardi Shaw, 1999: 371 . Type locality: USA: Idaho, Canyon Co., Parma. Holotype, female (ESWU), not seen, labelled: “ Idaho, Canyon County , Parma, 4 August 1997, C. R. Baird, host: L. hesperus Knight nymph swept in alfalfa, emerged 3 September 1997.

Diagnosis. Clypeus black or dark brown, not densely punctate (especially between lateral ocellus and inner eye margin), forewing vein r generally absent, and a multivoltine life cycle associated with all generations of Lygus .

Description. FEMALE. Colour. Head, mesosoma and metasoma black. Legs generally straw coloured, metacoxa brown to black; basal 0.3–0.5 of metatibia usually straw coloured or occasionally light reddish brown, and apical 0.5–0.7 of metatibia, and metatarsomere 1 clearly darker than basal 0.3–0.5 of metatibia, but metatarsomeres 2–5 less dark than metatarsomere 1. Palpi, tegula and mandible (except apex) straw coloured. Scape to flagellomere 2 straw coloured, thereafter brown to dark brown. Stigma dark brown and straw coloured in basal 0.3.

Structure. Flagellum with 18–20 flagellomeres (respectively 12%, 73% and 12% of 17 specimens) and flagellomeres enlarged in apical 0.5. Few of the preapical flagellomeres subquadrate (none 3%, one 15%, two 9%, three 29% and four 44% of 34 specimens). Length of gena behind eye 0.91–1.09 times as long as length of eye. Height of eye 1.34–1.52 times as long as minimum distance between inner eye margins (as in Fig. 18 ). Maximum width of head behind eyes subequal (0.93–0.97) to maximum head width at eye level. Occipital carina developed in dorsal third. Metasomal tergum 1 with lateral edges clearly convergent (posterior margin 2.1–2.4 times as wide as narrowest width near base) and elongate (medial length of tergum 1.5–1.7 times maximum width at posterior end). Radial cell length 0.94–1.13 as long as stigma width (as in Figs. 58–63 ). Forewing vein r in most specimens not developed (78% based on 100 specimens) and short ( Fig. 59, 60 ), and basal cell of forewing (except extreme base) pubescent (as in Fig. 54 ).

Sculpture. Punctures on vertex 5–10 µm in diameter, on frons and mesoscutum about 10–15 µm in diameter (a little larger than diameter of ommatidia). Punctures 20–25 µm apart on vertex (especially between lateral ocellus and inner eye margin), 5–15 µm apart on frons to 5–10 µm apart near antennal socket, and 20–25 µm apart on mesoscutum. Punctures on mesopleuron generally dense, occasionally scattered. Clypeus generally smooth, rarely punctate all over. Metasomal tergum 1 with about 10–12 longitudinal ridges, these often anastomosing on disc and forming a puncture­like sculpture.

MALE. Unknown.

Taxonomic notes. The holotype was not seen, but several specimens reared in a laboratory colony in Delaware originating from the type locality have been studied. The lack of r vein in the forewing, discovered by Shaw ( Day et al. 1999), applies to the holotype. The character is not seen in all specimens of this species studied and it also shows up frequently in adults of closely related species. Nevertheless, evidence discussed below supports its specific status.

Adults of P. howardi are most similar to those of P. broadbenti . Almost no structural differences were found between P. howardi and P. broadbenti . Adults of P. howardi differ from those of P. broadbenti in the development forewing vein r, the lack of males, and a multivoltine life cycle. A summary of measurement differences between P. broadbenti and P. howardi is given in Table 17.

Almost no structural differences were found between P. howardi and P. gillespiei . Adults of P. howardi differ from those of P. gillespiei in the development of the forewing vein “r”, males unknown, and the multivoltine life cycle. A summary of measurement differences between P. howardi and P. gillespiei is given in Table 17.

Adults of P. howardi could easily be confused with those of P. braunae a darkly coloured species. They are easily distinguished from those of P. braunae by the colour of the clypeus and metatibia, by the puncture density on the vertex especially between the lateral ocellus and the inner eye margin, by the the ratio of eye height to minimal distance between eye inner margins, and the ratio of length of flagellum to maximum width of head between outer eye margins.

Host and biological notes. Adults of P. howardi have been reared from field­collected Lygus hesperus and in the laboratory on L. lineolaris ( Day et al. 1999) . Adults occur from early May to late September with peaks of abundance probably in mid June, late July, and early September. This is a multivoltine species. Females of this species parasitize nymphs of all generations of Lygus .

Material examined and range. 56 (56♀) adults were studied. All were reared from Miridae . The species is known from the northern portions of the Great Basin in Idaho and Washington.

USA. DE: Newark , Laboratory colony from ID, Canyon Co., Parma (52♀; CNCI, USDA, USNM) . ID: Canyon Co., Parma (5♀, not seen; ESUW) . WA: Benton Co., EWSU Exp. Station N of Prosser (4♀; ESWU, CNCI) .

Figures

FIGURES 59–66. 59–63. Radial cell and stigma of forewing. 64. Hind wing. 65–66. Basal and subbasal cells of hind wing.

FIGURES 13–24. 13–22. Frontal view of head. Code: “a” ventral edge of clypeus. 23–24. Dorsal view of head.

FIGURES 50–58. 50–52. Forewing. 53–54. Basal and subbasal cells of forewing. 55–58. Radial cell and stigma of forewing.