Megastigmus pistaciae Walker, 1869

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 : 185-188

Megastigmus pistaciae Walker

(figures 9, 22, 39, 59, 78, 116, 135, 154)

Megastigmus pistaciae Haliday, Walker, 1869: 313 [nomen nudum].

Megastigmus pistaciae Walker, 1871: 35 . 2 Syntypes X, ‘South of France, on Pistacia terebinthus, M. Joudras coll.’ and ‘Tuscany on Pistacia lentiscus ’ (BMNH [examined]).

Trogocarpus ballestrerii Rondani, 1877: 35 . Lectotype X (Boucĕk, 1974: 245), Italy (La Specola, Firenze [not examined]). Synonymy by Masi, 1934: 210.

Female

Body length (without ovipositor) 3.4 and 3.5 mm. Body colour predominantly pale yellow. Head entirely pale yellow. Pilosity pale on lower face, black on remainder of head. Antenna mostly brownish; scape and pedicel yellowish. Thorax mostly pale yellow; pronotum and mesonotum pale yellow with longitudinal, somewhat indistinct red-brownish stripes; metanotum and scutellum darker, orange to red-brownish. Pilosity black on thoracic dorsum. Legs yellowish. Forewing stigma light brown. Propodeum dark orange. Gaster mostly orange-yellow. Ovipositor sheaths black.

Head about 1.1× as broad as long in dorsal view. Antennal scape elongate, as long as the combined length of pedicel, anellus, first funicular segment and one-half of second funicular segment; funicular segments 1–3 about 1.6× as long as wide, then tending to subquadrate (figure 22). Pronotum and mesoscutum with regular cross-striae. Scutellum elongate, 1.4× as long as broad, the anterior part with cross-striae tending to reticulation, the frenal area with longitudinal carinae (figure 135). Forewing stigma oval-oblique, 1.2× as long as wide; upper part of stigmal vein comparatively short, 0.2× as long as stigma length; uncus as long as upper part of stigmal vein (figure 59). Propodeum without median carina. Ovipositor sheaths much shorter (0.5×) than body, nearly 0.6× as long as gaster and thorax combined, 1.1× as long as gaster. Distal part of the dorsal valve of the ovipositor with the third median tooth enlarged (figure 9).

Male

Body length 3.3mm. Body predominantly yellow with a few dark parts. Head entirely yellow. Pilosity pale on lower face, but black on parascrobal area and vertex. Antenna mostly brownish with scape yellowish. Thorax entirely yellow with long, black bristles; four bristles in arched rows along lateral margins of scutellum. Legs yellowish. Wings subhyaline; forewing stigma dark brown, darker than in female. Propodeum yellow. Gaster quite entirely black with yellow spots on first apparent and last tergum.

Head rounded, nearly 1.2× as wide as long in dorsal view. Antennal scape elongate, 1.2× as long as the combined length of pedicel, anellus and the first two funicular segments; funicular segments more elongate than in female, about twice as long as wide (figure 39). Mid-lobe of mesoscutum very elongate, about 1.8× as long as broad, more than 2× longer than the transcutal line; pronotum and mesoscutum with regular cross-striae; scutellum 1.3× as long as broad, the anterior part with coarse cross-striation tending to reticulation, the frenal area with arcuate wrinkles (figure 154). Stigma oval-oblique, about 1.4× as long as wide; upper part of stigmal vein about 0.3× as long as stigma length; uncus as long as upper part of stigmal vein (figure 78). Propodeum without median carina. Aedeagus truncated, digitus with three teeth (figure 116).

Variation

The above description is based on the type material of M. pistaciae for female and, for male, on a specimen from Ceriale nr Albenga, Italy (3 September 1972, Z. Boucĕk leg., MNHN). In the other examined specimens, body length varied from 2.6 to 3.5 mm in females, from 2.0 to 3.5 mm in males. Female colour ranged from whitish in pale specimens to rust-yellow in darker ones. Males were more variable in colour than females, with forms much darker than the type material. In these forms, head, margins of mesoscutum, propodeum and coxae were black. Gaster could be yellow to brownish yellow with a dorsal black line more or less extending laterally on the first four terga (Zerova and Seryogina, 1994) .

Sex ratio

Reproducing by thelythokous parthenogenesis. Males were very scarce (less than 1 W: 1000 X) in rearings of pistaccio nuts from Europe, North Africa and Iran but De Stefani (1917) noticed ratios of 6 W:760 X in Pistacia vera and 1 W:37 X in P. terebinthus in Italy. Males seemed more common in the USA (58 X: 1356 X, i.e. 4.1% of males, caught in yellow traps at Chico, CA, Rice and Michailides, 1988; 3 W:50 X emerged from pistaccio nuts, Placerville, CA, AR).

Hosts

Develops in seeds of Pistacia spp. (Anacardiaceae) . In the native areas, recorded from P. atlantica (Davatchi, 1958; AR), P. integerrima (Rice and Michailides, 1988) , P. lentiscus (Agnostopoulos, 1938; AR), P. mutica (Nikol’skaya, 1935, 1952; Davatchi, 1956, 1958; Lozovoi, 1965; Zerova and Seryogina, 1994), P. terebinthus (De Stefani, 1908, 1917, 1918; Agnostopoulos, 1938; Davatchi, 1956; AR) and P. vera (De Stefani, 1917, 1918; Nikol’skaya, 1934, 1935, 1952; Davatchi, 1956, 1958; Jarraya and Bernard, 1971; Çanakçioglü, 1993; Zerova and Seryogina, 1994; USNM). It shifted on exotic P. chinensis introduced to California (Rice and Michailides, 1988). The pinkpepper tree, Schinus molle , was also listed as a host (Furth, 1985 in Grissell, 1999; Rice and Michalides, 1988) but confusion with a peppertree seed chalcid, M. transvaalensis , may have occurred. Previous records on Eucalyptus (e.g. Escherich, 1938, 1942) are probably erroneous.

Distribution

Coastal Mediterranean areas to Afghanistan (USNM), Iran (Davatchi, 1956, 1958; Abai and Adeli, 1984) and China (USNM). Introduced to California (Rice and Michailides, 1988; AR) and Mexico (USNM). In Europe, known from Bulgaria (Boucĕk, 1977); Cyprus (Rice and Michailides, 1988); France: southern part including Corsica (Davatchi, 1956, 1958; AR); Greece (Agnostopoulos, 1938; AR); Italy including Sicily (De Stefani, 1908, 1917, 1918; Greco and Nucifora, 1999; AR); Israel (Furth, 1985 in Grissell, 1999; USNM); Portugal (AR); former Soviet Union: from Crimea and Transcaucasia to Turkmenia and Uzbekistan (Nikol’skaya, 1934, 1935, 1952; Lozovoi, 1965; Nikol’skaya and Zerova, 1978; Zerova and Seryogina, 1994; USNM); Turkey (Schimitschek, 1944; Özkazanç, 1982; Çanakçioglü, 1993); Ukraine (Lozovoi, 1965); former Yugoslavia: Croatia, Montenegro (Boucĕk, 1977; AR). Also observed in North Africa: Algeria (USNM); Morocco (Davatchi, 1958); Tunisia (Jarraya and Bernard, 1971; AR).

Comments

No other Megastigmus species is yet known to develop in Pistacia seeds in the West Palearctic but two species of Eurytomidae ( Eurytoma pistaciae Rondani and E. plotnikovi Nikol’skaya) compete for the resource in the major part of the distribution area (Davatchi, 1956, 1958; Jarraya and Bernard, 1971; Boucĕk, 1974, 1977). M. pistaciae can be easily recognized by the large stigma on forewing.

Material examined

Afghanistan: 1 X, PQ, US quarantine service ( USNM) . Algeria: 1 X, ex. P. lentiscus, US quarantine service Miami ( USNM) . China: 1 X, 1 W, ex. ‘seeds of Pistacia ’, EQ# 059182, 3 June 1938, US quarantine service ( USNM) . Croatia: 43 X, ex. P. terebinthus, Gruda , August 1989 ( AR) . France: 1 X syntype, ex. P. terebinthus , south of France , M. Joudras ( BMNH) ; 15 X, ex. Pistacia lentiscus, Rognes (13), August 1990, ( AR) ; 15 X, ex. P. terebinthus, Saint-Chinian (34), July 1990, ( AR) ; 20 X, ex. P. terebinthus , Menton (06), August 1992 ( AR) ; 1 X, ex. P. lentiscus , December 1950, J. Ghesquière ( MNHN) ; 15 X, ex. P. terebinthus, La Ciotat (13), August 1993, ( AR) ; 13 X, ex. P. terebinthus, Fréjus (83), August 1992 ( AR) ; 22 X, ex. P. terebinthus, Rondinara (Corsica) , July 1987 ( AR) . Greece: 39 X, ex. P. terebinthus, Pylos , August 1991 ( AR) . Israel: 1 X, ex. P. terebinthus , ‘ Palestine’ , PQ, US quarantine service ( USNM) . Italy: 1 X syntype, ex. P. lentiscus , Tuscany ( BMNH) ; 1 W, Ceriale nr Albenga , 3 September 1972, Z. Boucĕk ( MNHN) ; 2 X, Sicily, 1911, De Stefani ( MNHN) . Mexico: 1 X, ex. seed Pistacia, Saltillo , May 1987, V. Carapia ( USNM) .

Portugal: 81 X, ex. P. terebinthus, Corveiro , 23–25 August 1993 ( AR) ; 44 X, ex. P. terebinthus , Cabo Espichel, 20–25 August 1993 ( AR) . Tunisia: 10 X, ex. P. atlantica, Sidi Khedr , 15 July 1995 ( AR) ; 10 X, ex. Pistacia lentiscus, Semeche , 25 July 1995 ( AR) ; 13 X, ex. P. terebinthus, Tabarka , 13 August 1987 ( AR) ; USA: 65 X, 3 W, ex. Pistacia sp. , Placerville, CA, 24 February 1994, N. Rappaport ( AR) ; 30 X, 1 W, ex. Pistacia chinensis, Placerville, CA , 15 April 2000 ( AR) . Uzbekistan: 1 X, ex. P. vera, Taschkent, PQ US quarantine service ( USNM) . Yugoslavia: 15 X, ex. P. terebinthus, Kotor (Crna Gora), August 1989 ( AR) .