Peristenus relictus (Ruthe)

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 : 35-37

Peristenus relictus (Ruthe)

( Figs. 8 habitus, 22, 44, 49, 57, Table 6)

Microctonus relictus Ruthe, 1856: 305 . Type locality: Germany. Lectotype, female (BMNH), not seen, designated by Richards, 1967: 177, and labelled (based on Loan, 1974b): “ Lectotype (British Museum (Nat. Hist.) lectotype label; B. M. Type Hym. 3C714; 59–101 Germany; 20; M. relictus Rut., Ruthe coll. 59–101; Microctonus relictus Ruthe 1856 , ♀. Lectotype Richards 1966”.

Leiophron relictus ; Richards, 1967: 177.

Peristenus relictus ; Loan, 1974b: 213.

Peristenus stygicus Loan, 1973: 272–273 . Type locality: Poland, Dziekanow Lesny (near Warsaw). Holotype, female ( Institute of Zoology , Polish Academy of Sciences, Warsaw), not seen . Paratypes seen: 9 males and 4 females ( CNCI and USNM) . Holotype reared from a nymph of Lygus rugulipennis , collected in 1967, and emerged in May 1969. Synonymy by Achterberg (2001: 378) .

Diagnosis. Mesoscutum mostly impunctate and hind legs dark brown to black.

Description. FEMALE. Colour. Body black ( Figs. 8 , 22 , 44, 49 ) occasionally with blackish red tinge on ventral surface of mesothorax or behind upper margin of eye. Leg colour variable. Typically: hind leg mainly dark brown with base of tibia reddish brown; mid leg with coxa, femur and mesotarsomere 5 brown, with tibia and tarsomeres 1–4 reddish brown; foreleg procoxa reddish brown with remainder of leg light reddish brown. In a few specimens legs either darker, with all coxae dark brown to black ( Fig. 49 ), pro­ and mesofemora and basal 0.5 of profemora dark brown, and tarsomere 5 of all legs brown, or paler with hind leg brown, and mid leg and forelegs light reddish brown. Scape, pedicel and flagellomeres 1, or 1 and 2 usually reddish brown, the following flagellomeres dark brown to black. Stigma dark brown and straw coloured in basal third.

Structure. Flagellum with 16–18 flagellomeres (respectively 8%, 74% and 18% of 100 specimens) and flagellomeres enlarged in apical 0.5. Length of gena behind eye 0.90–1.05 times as long as length of eye. Height of eye 1.2–1.3 times as long as minimum distance between inner eye margins. Maximum width of head behind eyes subequal (0.93–0.97) to maximum head width at eye level. Occipital carina not developed in dorsal 0.3. Metasomal tergum 1 with lateral edges clearly convergent (posterior margin 1.7–2.3 times as wide as narrowest width near base) and elongate (medial length of tergum 1.7–2.1 times maximum width at posterior end). Radial cell length 0.5–0.8 times as long as stigma width. Forewing vein r lacking, and basal half of basal cell sparsely pubescent, glabrous in spots and distinctly less pubescent than 1 st discal cell.

Sculpture. Punctures on vertex from 10–15 µm to commonly 20–25 µm in diameter, frons and mesoscutum about 20–25 µm in diameter (a little smaller than diameter of ommatidia). Punctures 40–80 µm apart on vertex, 25–40 µm apart on frons, and 15–25 µm apart near antennal socket, 25–75 µm apart on anterior 0.3 of mesoscutum. Punctures on mesopleuron generally scattered or occasionally dense, forming a horizontal row and/or carina above mesocoxa. Clypeus generally glabrous except for row of long setae along anterior margin. Metasomal tergum 1 with about 10–12 longitudinal ridges, these often anastomosing on disc and forming a puncture­like sculpture.

MALE. Colour. As in female.

Structure. Flagellum with 17–19 flagellomeres (respectively 22%, 55% and 23% of 100 specimens) and flagellomeres narrow in apical 0.5. Height of eye 0.88–1.0 times as long as minimum distance between inner eye margins. Otherwise structure and sculpture as in female.

Taxonomic notes. Adults of P. relictus differ from those of any known North American species by the puncture development on the mesoscutum, and hind leg colour. A summary of measurement differences between P. relictus and P. digoneutis is given in Table 6.

Adults of P. relictus differ from those of P. rubricollis by puncture development on the posterior 0.7–0.8 of mesoscutum ( Fig. 44 ), the face colour ( Fig. 22 ), the spot development behind eye of females ( Fig. 8 ), the head colour of males, and the leg colour (especially hind legs) ( Figs. 8 , 49 ). A summary of measurement differences between P.relictus and P. rubricollis is given in Table 6.

Host and biological notes. In Europe, adults of this species have been reared from nymphs of species from a wide variety of tribes and subfamilies of Miridae . Adults have been recorded from all species of Lygus studied. In North America, this species has been reared mainly from nymphs of Lygus lineolaris in the laboratory, and Lygus shulli Knight in the field in California. Adults occur from May to early September in Europe with peaks of abundance in early June and in late July. This is a bivoltine species.

Material examined and range. About 850 adults were studied. Of these, 565 were from Europe, 284 reared from laboratory colonies from Europe and North America and 31 reared (15♂, 16♀) from North America. There have been several attempts at establishing this species. C. H. Pickett proved its establishment in 2001 around Sacramento and in 2002 in Santa Cruz County. For the history of introduction into North America see Ball et al. (1999), Pickett et al. (1998, 2000, 2002). The species is known from three counties in California.

USA. CA: Monterey Co., Castroville (8♂, 8♀; CNCI, CDFA) ; Sacramento Co., Sacramento 38º35.607'N 121º29.519'W (4♂, 4♀; CNCI, CDFA) ; Santa Cruz Co., Harkins slough (4♂, 3♀; CNCI, CDFA) .

Figures

FIGURES 6–12. 6–9. Habitus with frontal view of head. Codes: “a” clypeal colour; “c” metacoxal colour; “f” metafemoral colour; “g” facial colour; “h” genal spot. 10–12. Lateral view of metatibia.

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

FIGURE 37–49. 37. Lateral view of antenna. 38–39. Last six flagellomeres in lateral view. 40–44. Dorsal view of mesosoma. 45–49. Lateral view of mesosoma.