Megastigmus pinsapinis Hoffmeyer, 1931

Roques, A. & Skrzypczyńska, M., 2003, Seed-infesting chalcids of the genus Megastigmus Dalman, 1820 (Hymenoptera: Torymidae) native and introduced to the West Palearctic region: taxonomy, host specificity and distribution, Journal of Natural History 37 (2), pp. 127-238 : 177-181

Megastigmus pinsapinis Hoffmeyer

(figures 7, 20, 57, 76, 96, 114, 133, 152)

Megastigmus pinsapinis Hoffmeyer, 1931b: 264 . Holotype X, Spain, 29 May 1930 (depository unknown).

Female

Body length (without ovipositor) 4.2 mm. Body colour black and yellow. Face, parascrobal area, circumorbital area and gena bright yellow, temple yellow with outer eye margin black; frons, vertex and occiput black. Pilosity on head mostly dark, with conspicuous pale bristles. Antenna brownish with scape and pedicel yellow with black markings. Thorax predominantly black except lateral panel of pronotum yellow, suture of prepectus and tegula light brown, mesopleuron dark brown with acropleuron and upper mesepimeron lighter. Pilosity black on thorax even on yellow parts. Legs yellow except hind coxa black, front and mid-tarsi brownish yellow. Propodeum black except callus brown, with pale pilosity. Dorsum of gaster black with limited lateral infuscations, remainder orange-yellow. Ovipositor sheaths black.

Head rounded in dorsal view, 1.2× as broad as long. Antennal scape 0.9× as long as pedicel, anellus and first funicular segment combined; first funicular segment elongate, 1.2× longer than the following segments (figure 20). Pronotum and mesoscutum with strong arched cross-striae. Scutellum 1.3× as long as broad, the anterior part with transverse cross-striae tending to reticulation, the frenal area weakly wrinkled (figure 133). Forewing stigma very elongate, 2.1× as long as broad; upper part of stigmal vein comparatively elongate, 0.9× as long as stigma length; uncus elongate, 1.2× longer than stigma width (figure 57). Propodeum with a curved median carina. Ovipositor sheaths 1.2× as long as body. Distal part of dorsal valve of ovipositor with blunt teeth (figure 96).

Male

Body length 3.9 mm. Body colour black and yellow. Face, parascrobal area and gena bright yellow, temple yellow with outer eye margin black; frons, vertex and occiput black. Head pilosity mostly black, even on lower face. Scape and pedicel shining black above, yellowish beneath; remainder of antenna brown. Thorax with dorsum entirely black but lateral and ventral parts mostly bright yellow, including lateral panel of pronotum, prepectus, tegula, acropleuron and mesopleuron; metapleuron black. Pilosity mostly black on thoracic dorsum but pale on callus. Legs mostly yellow except hind coxa with longitudinal black patches on outer surface and conspicuous black dots at base of bristles on inner surface; pilosity pale on coxa. Propodeum black except callus yellow with conspicuous black dots at base of bristles. Gaster mostly bright yellow with a black dorsum extending laterally in three distinct, large, triangular stripes.

Head about 1.1× as broad as long in dorsal view. Antennal scape 0.9× as long as pedicel, anellus and first funicular segment; first funicular segment elongate, about 2× as long as wide, the following segments tending to subquadrate (not figured— see Pintureau et al., 1991). Pronotum and mesoscutum with strong cross-striae. Scutellum 1.3× as long as broad, the anterior part with coarse cross-striae and the frenal area with weak irregular wrinkles (figures 7, 152). Forewing stigma elongateoval, 1.6× as long as broad; upper part of stigmal vein comparatively elongate, 0.5× as long as stigma length; uncus short, 0.5× as long as upper part of stigmal vein (figure 76); basal cell closed with 35 bristles. Propodeum with a median carina interrupted in the middle (figure 7). Aedeagus small, rounded, digitus with four small teeth (figure 114).

Variation

The above description is based for female on a specimen emerged from Abies pinsapo (June 1858, coll. Sichel) and for male on a specimen emerged from Cedrus atlantica (Barjac, France, 25 May 1997, J. P. Fabre leg.) both deposited at MNHN. In the other examined specimens, body length varied from 4.0 to 5.6 mm in females, from 3.9 to 4.2 mm in males. Only the colour of lateral parts of thorax was variable in females, prepectus, acropleuron and upper mesepimeron being entirely yellow in some specimens from southern France. Mid-coxa could show black patches and hind coxa could be entirely yellow beneath. Specimens from southern France observed by Hussey (1957) also presented distinct longitudinal carinae across the frenal area.

No variation in male colour was observed but a few French specimens showed an asymmetrical morphology: presence of five teeth on the left digitus versus four teeth on the right one (Pintureau et al., 1991), presence of a female-like stigma (2× as long as broad) on the right forewing versus a male-like stigma (1.6× as long as broad) on the left one (Marcelly Forest, AR).

Sex ratio

Mostly reproducing by thelytokous parthenogenesis (Pintureau et al., 1991). Males are very scarce, about 1 W:4000 X (Fabre et al., 1994).

Hosts

Develops in seeds of both cedars ( Cedrus spp. ) and some European firs ( Abies spp. ) ( Pinaceae ). Observed in the natural range of Cedrus atlantica (Milliron, 1949; El Hassani and Messaoudi, 1986; Pintureau et al., 1991; Bouaziz, 1993; Bouaziz and Chakali, 1998) and Abies pinsapo (Hoffmeyer, 1931b) . It has extensively colonized the plantations of C. atlantica and A. pinsapo in southern France (Berland, 1950; Hussey, 1957; Roques, 1983; Fabre, 1986, 1989; Pintureau et al., 1991; AR) and Italy (USNM). In French arboreta, it also attacked other exotic cedars ( C. brevifolia , C. deodara and C. libani ), the introduced Caucasian fir, A. nordmanniana and the native A. alba (Roques, 1983; Ostermeyer, 1990; AR).

Distribution

Originating from North Africa and/or Spain; probably introduced to France with cedar seeds (Pintureau et al., 1991). The present range covers the major part of the western Mediterranean basin, but the species is also present in more northern locations (e.g. north-central France; Roques, 1983). Recorded from Algeria (Pintureau et al., 1991; Bouaziz, 1993; Bouaziz and Chakali, 1998); France (Berland, 1950; Hussey, 1957; Roques, 1983; Fabre, 1986, 1989; Pintureau et al., 1991); Italy (USNM); Morocco (Roques, 1983; El Hassani and Messaoudi, 1986; El Hassani et al., 1994) and Spain (Hoffmeyer, 1931b).

Comments

Two other species, M. schimitscheki and more scarcely M. suspectus , are capable of attacking seeds of Cedrus spp. in the West Palearctic. The face colour allows the females of the three species to be differentiated. It is entirely yellow in M. pinsapinis whereas that of M. suspectus always shows more or less extended black markings, and that of M. schimitscheki is entirely black except the oral area orange-brown. M. schimitscheki also differentiates from the two others by the thorax colour (entirely black versus presence of lateral yellow spots in the two others), the sculpture of the frenal area (mostly smooth with a few short longitudinal carinae versus wrinkled), and a less elongated forewing stigma (1.6× as long as broad versus 1.7–2.2×). The female of M. pinsapinis differs from that of M. suspectus by a shorter black spot on temple, which never reaches gena (versus extending to gena in the other species), the colour of some lateral parts of thorax (prepectus, tegula and acropleuron yellow to light brown versus black), and the colour of coxae (fore-coxa yellow; mid-coxa yellow sometimes with black markings; hind coxa brownish to black with yellow markings versus all coxae black with the distal parts of fore- and mid-coxa yellow).

Males of M. schimitscheki differ by the thorax and coxae entirely black whereas lateral parts of thorax and coxae are partly yellow in the two other species. Males of M. pinsapinis always present a yellow hind coxa whereas this coxa is black in M. suspectus .

A total of six other species compete for fir seeds. Diagnostic characters are given in the chapter regarding M. milleri .

Material examined

Algeria: 2 X, ex. Cedrus atlantica, Chréa , May 1993, K. Bouaziz ( AR) . France: 4 X, ex. A. alba, Les Barres (45), May 1981 ( AR) ; 5 X, ex. Abies nordmanniana, Amance arboretum (54), June 1982 ( AR) ; 1 X, ex. A. pinsapo , June 1858, Sichel ( MNHN) ; 15 X, ex. A. pinsapo, Catus (46), May 1982 ( AR) ; 1 W, ex. C. atlantica, Barjac (30), 25 May 1997 ( JPF) ; 1 W, ex. C. atlantica, Marcelly (11), 30 April 1999 ( JPF) ; 9 X, ex. C. atlantica, Les Barres , May 1981 ( AR) ; 62 X, ex. C. atlantica, Mt Ventoux , 15 May 1980 ( JPF) ; 12 X, ex. C. atlantica, Mt Ventoux (84), 15 May 1993, French National Forestry Office ( AR) ; 3 X, ex. C. brevifolia, Les Barres , May 1990, R. Ostermeyer ( AR) ; 3 X, ex. C. deodara, Les Barres , June 1989 ( AR) ; 2 X, ex. C. libani, Les Barres , May 1981 ( AR) ; 10 X, ex. Cedrus sp. , Apt (84), J. Gobert, 1947 ( MNHN) . Italy: 1 X, ex. C. atlantica, PQ, US quarantine ( USNM) . Morocco: 2 X, ex. C. atlantica, Azrou , May 1985, A. El Hassani ( AR) .