Peristenus digoneutis Loan, 1973

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 : 32-34

Peristenus digoneutis Loan

( Figs. 6 habitus, 19, 25, 31, 32, 43, 45, 68, 77, 78, 79, 80, 81, 82, 84, 87, Table 5)

Peristenus digoneutis Loan, 1973: 273–274 . Type locality: Poland, Dziekanow Lesny (near Warsaw). Holotype, male ( Institute of Zoology , Polish Academy of Sciences, Warsaw), not seen.

Holotype reared from a nymph of Lygus rugulipennis Poppius , collected in 1969, and emerged in May 1970. Paratypes seen: 9 males and 4 females ( CNCI and USNM) .

Diagnosis. Mesoscutum densely punctuate, without occipital carina in upper third of head, metacoxa straw coloured, and flagellum with 17–19 flagellomeres in females, and 17–20 in males.

Description. FEMALE. Colour. Body colour variable. Typical specimens coloured as follows: head dark brown or black except for light reddish brown clypeus, face, and lower 0.3 of gena, and reddish brown along inner, upper and dorsal portion of outer margin of eye ( Figs. 6 , 19 , 25 , 84 ); mesosoma dark brown or black except for reddish brown or brown on posterodorsal corner of pronotum and anteroventral corner of mesepisternum ( Fig. 45 ); metasoma brown, but paler at side and ventrally ( Fig. 77 ). Rarely, body completely black, or body brown with head, prothorax and mesothorax light reddish brown. Legs, palpi and tarsomere 5 straw coloured (as in Fig. 11 ). Flagellum straw coloured at base becoming reddish brown in apical 0.3–0.6. Stigma brown and straw coloured in basal third (as in Fig. 60 ).

Structure. Flagellum with 17–19 flagellomeres (respectively 5%, 43% and 52% of 100 specimens) and flagellomeres enlarged in apical 0.5. Length of gena behind eye 0.9–1.1 times as long as length of eye. Height of eye 1.25–1.4 times as long as minimum distance between inner eye margins. Maximum width of head behind eyes subequal (0.94–0.96) to maximum head width at eye level. Occipital carina not developed in dorsal third or at most suggested by shallow transverse sculpture ( Fig. 32 ). Metasomal tergum 1 with lateral edges clearly convergent (posterior margin 2.0–2.9 times as wide as narrowest width near base), and elongate (medial length of tergum 1.4–1.8 times maximum width at posterior end) ( Fig. 68 ). Radial cell length 0.8–1.1 as long as stigma length (as in Fig. 58 ). Forewing vein r lacking (as in Figs. 57 , 59, 60 ) or vein rarely developed, and basal cell almost completely densely pubescent and about as densely pubescent as first discal cell.

Sculpture. Punctures on vertex, frons and mesoscutum about 7–15 µm in diameter (similar to diameter of ommatidia). Punctures 20–30 µm apart on vertex and 10–20 µm apart on frons, 15–30 µm apart on mesoscutum. Punctures on mesopleuron varying from almost completely smooth to very densely punctate. Clypeus generally glabrous except for row of long setae along anterior margin. Metasomal tergum 1 with about 10–12 longitudinal ridges, these commonly anastomosing on disc and forming a puncture­like sculpture ( Fig. 68 ).

MALE. Colour. As in female, but body of males often paler.

Structure. Flagellum with 17 to 20 flagellomeres (respectively 1%, 35% 54% and 10% of 100 specimens) and flagellomeres narrow in apical half. Height of eye subequal (0.88–1.0) to minimum distance between inner eye margins. Otherwise structure and sculpture as in female.

Geographical variation. At the northern limit of its range (e.g., in southern Quebec and northern Germany) or in mountain regions (e.g., Austria), a few specimens with complete black body have been found. In these regions, intermediate colour patterns are seen in many individuals.

Taxonomic notes. Adults of P. digoneutis have been confused with those of P. rubricollis (Thomson) ( Loan 1973) . Loan (1973) correctly segregated the two species on colour pattern and number of flagellomeres. In addition, the two species differ in the preferred mirid hosts and in their life cycle. A summary of measurement differences between P. dignoneutis and P. rubricollis is given in Table 5.

Adults of P. digoneutis differ from those of P. relictus in puncture development on the mesoscutum, face and leg colour, and the length of the radial cell. A summary of measurement differences between P. digoneutis and P.relictus is given in Table 5.

Host and biological notes. In Europe, P. digoneutis has been reared from several Stenodemini and Mirini species. The attack level is extremely low except for Lygus and Adelphocoris hosts ( Haye et al. 2005). In North America, P. digoneutis has been reared mainly from nymphs of Lygus lineolaris and Adelphocoris lineolatus and only once from a nymph of Leptopterna dolobrata (Linnaeus) . Adults have been recorded from May (late May in cold temperate regions) to September with peaks of abundance in early June and in late July ( Loan and Bilewicz­Pawinska 1973). This is a bivoltine species.

Material examined and range. Over 6,800 adults were studied. Most specimens were left in cold storage. About 1,800 specimens were pinned and mounted, about 960 from Europe and 823 (339♂, 360♀ and 125♂ / ♀) from North America. We have included W. H. Day published records as “( WHD)” with no reference to the number of specimens ( Day et al. 1998, 2000, 2003). We have seen many of these specimens and they were all correctly identified. Several attempts at introducing this species from Europe were made between 1979 and 1988. By 1984, it was certainly established at Warren Co., New Jersey. Day et al. (1990, 1998, 2000, 2003) recorded the history of its introduction into North America and its subsequent expansion. Based on specimens submitted by C. Pickett in 2003 this species was successfully established at two sites in California. In eastern North America , the species has been encountered within a rectangle formed by northern New Jersey, southern Quebec, Nova Scotia and southern Ontario. The northernmost record, Bois Francs, QC, is at the northern end of the sugar maple range at the southern fringes of the boreal ecozone .

CANADA. NS: near Berwick , 45º01.846'N 64º46.185'W (1♂) . ON: London (6♂, 8♀) ; near Mountain , 45º02'02''N 75º27'10''W (2♂, 2♀) ; Ottawa (2♀) . QC: near Bois Francs , 46º32'45''N 75º57'04''W (1♀) ; near Hemmingford , 45º02'41''N 73º31'54''W (20♂, 11♀) ; near Hemmingford , 45º00'56''N 73º32'11''W (57♂, 65♀) ; near Riviėre Ouelle , 47º25.657'N 70º00.989'W (1♀) ; near Ste. Clotilde , 45º10'05''N 73º40'53''W (231♂, 230♀) ; near St. Cyrille­de­Wendover , 45º57.258'N 72º27.846'W (1♂) . USA. CA: Sacramento Co., Sacramento (3♂, 3♀; CDA, CNCI) ; Santa Cruz Co., Harkins slough (1♀; CDFA) . CT: Hartford Co., near Suffield ( WHD) ; Lichtfield Co., near Bakers field ( WHD) . DE: New Castle Co., Newark (14 ♂ / ♀; USDA) . MA: Franklin Co., near Deerfield ( WHD) ; Hampden Co., near Agawam ( WHD) . ME: Kennebec Co., near E. Monmouth ( WHD) ; Oxford Co., near Fryeburg ( WHD) . NH: Belknap Co., near Belmont ( WHD) ; Carroll Co., near E. Conway ( WHD) ; Coos Co., near Twin Mountain ( WHD) ; Grafton Co., near Orford ( WHD) ; Hillsboro Co., near Milford ( WHD) ; Merrimac Co., near Concord ( WHD) ; Rockingham Co., near Epping ( WHD) ; Strafford Co., near Madbury ( WHD) . NJ: Blairstown (2♂, 1♀, 76♂ / ♀; USDA) ; Branchville (1; USDA) ; Hamburg (3♂ / ♀; USDA) ; Newton (8♂, 8♀: USDA) ; Rancocas (9♂ / ♀; USDA) ; Squire Corner (1♂ / ♀; USDA) ; Vernon (1♂ / ♀; USDA) ; Woodstown (1♂, 3♂ / ♀; USDA) ; Gloucester Co., Aura (1♀; USDA) ; Morris Co., near Long Valley ( WHD) ; Hunterdon Co., near Hampton ( WHD) ; Mercer Co., near Pennington ( WHD) ; Sussex Co., near Fredon ( WHD) ; Warren Co., near Marksboro ( WHD) . NY: Albany Co., Albany (4♂, 3♀), Preston Hollow ( WHD) ; Broome Co., near Itaska ( WHD) ; Cataraugus Co., near Great Valley ( WHD) ; Cayuga Co., near Scipio Center ( WHD) ; Chenango Co., near Norwich ( WHD) ; Clinton Co., near W. Chazy ( WHD) ; Columbia Co., near Hudson ( WHD) ; Cortland Co., near Marathon ( WHD) ; Delaware Co., near Lake Placid ( WHD) ; Dutchess Co., near Hibernia ( WHD) ; Greene Co., near Coxsackie ( WHD) ; Madisson Co., near Nelson ( WHD) ; Oneida Co., near Paris station ( WHD) ; Onondaga Co., near Pompey ( WHD) ; Otsego Co., near Richfield Station ( WHD) ; Rensselaer Co., 42º55.296'N 73º35.011'W (11♀), near Poestenkill ( WHD) ; Saratoga Co., near Waterford ( WHD) ; Schoharie Co., near N. Blenheim ( WHD) ; Schuyler Co., near Burdett ( WHD) ; Seneca Co., near Fayette ( WHD) ; Steuben Co., near Bath ( WHD) ; Sullivan Co., near Roscoe ( WHD) ; Tioga Co., near Berkshire ( WHD) ; Tompkins Co., Ithaca (1♀; CNCI) , near Lansing ( WHD) ; Washington Co. , 43º10.362'N 73º30.025'W (1♀; CNCI) ; 42º21.221'N 73º32.365'W (3♂, 11♀), near Easton ( WHD) ; Wyoming Co. , near Silver Springs ( WHD) . PA: Bradford Co., near Terrytown ( WHD) ; Carbon Co., near Beltzville ( WHD) ; Columbia Co., near Benton ( WHD) ; Luzerne Co., near Conyngham ( WHD) ; Lycoming Co., near Calvert ( WHD) ; Monroe Co., near Kresgville ( WHD) ; Northampton Co., near Windgap ( WHD) ; Northumberland Co., near Elysburg ( WHD) ; Potter Co., near Brookland ( WHD) ; Sullivan Co., near Dushore ( WHD) ; Susquehanna Co., near Dundaff ( WHD) ; Tioga Co., near Wellsboro ( WHD) ; Wyoming Co. , near Factoryville ( WHD) . VT: Bennington Co., near S. Schaftbury ( WHD) ; Essex Co., near Lunebrug ( WHD) ; Windham Co., near Vernon ( WHD) .

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.

FIGURES 25–36. 25–27. Dorsal view of head with insert to show sculpture. 28–31. Lateral view of head. 32–33. Posteroir view of head. Code: “a” dorsal end of occipital carina. 34. lateral view of antenna. 35–36. Last five flagellomeres in lateral view.

FIGURES 79–87. 79–80. Frontal view of head (MnEy­Ey = minimum eye distance). 81–82. Lateral view of head (GL = genal length, EyL = eye length, EyH = eye height). 83–84. Dorsal view of head (LOL lateral ocelli length, POL posterior ocelli length, OOL ocellar ocular length, MxHdW = maximum head width, MxGW = maximum genal width). 85. Radial cell and stigma of forewing (RcL = radial cell length, StW = stigma width). 86. Lateral view of seven last flagellomeres (L= length, W = width). 87. Dorsal view of metasomal tergum 1 (L = length, MxW = maximum width, MnW = minimum width).

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.

FIGURES 67–78. 67–68. Dorsal view of metasomal tergum 1. 69–70. Ventral view of metasomal segment 1. 71–72. Lateral view of seven last flagellomeres. 73–74. Lateral view of first three flagellomeres. 75–76. Dorsal view of protarsus. 77–78. Lateral view of metasoma.

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

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