Megastigmus rosae Boucĕk, 1971

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 : 193-195

Megastigmus rosae Boucĕk

(figures 24, 61, 99, 137) Megastigmus pictus of Wachtl, 1884: 214 (according to Boucĕk, 1970b) [misidentification]. Megastigmus pictus of Hoffmeyer, 1931b: 265 (according to Boucĕk, 1970b) [misidentification]. Megastigmus rosae Boucĕk, 1971: 43–44 . Holotype X, Botanical Garden, Wien, A, Novitzky

leg. (BMNH [examined]).

Female

Body length (without ovipositor) 2.4 mm. Colour mainly yellowish with brownish black markings. Head yellowish with a broad dark brown spot extending on vertex including the ocelli, and connected with extensively dark occiput. Pilosity pale on lower face, black on head dorsum. Antenna brown with scape yellowish beneath. Pronotum mainly yellow; whole mid-lobe and anterior part of lateral lobes of mesoscutum, whole scutellum, axilla (except a spot at inner corner), metanotum, mesopleuron, metapleuron and propodeum dark brown to black. Pilosity dark on thoracic dorsum. Legs mainly yellowish, with hind coxa black basally. Propodeum brown with a black band on anterior margin. Gaster dorsally brownish with faintly indicated cross-bands but sides mainly yellowish. Ovipositor sheaths black.

Head 1.5× as broad as long in dorsal view, with the eyes hardly protruding. Antennal scape elongate, 1.3× as long as pedicel, anellus and first funicular segment combined; pedicel 1.8–1.9× as long as broad, longer (1.2×) than first funicular segment (figure 24). Pronotum and mesoscutum with fine cross-striae. Scutellum fewly elongate, 1.1× as long as broad, the anterior part reticulate-striate, the frenal area nearly smooth with short carinae extending longitudinally from both the frenal line and the hind margin (figure 137). Forewing stigma rounded, about 1.2× as long as broad, with an upper part of stigmal vein longer (1.4×) than uncus (figure 61); basal cell with disc bearing 7–10 hairs. Propodeum with a rather straight, double median carina. Ovipositor sheaths distinctly smaller (0.7×) than body, 0.9× as long as gaster and thorax combined. Distal part of dorsal valve of ovipositor with strong median teeth, the third one being larger than others (figure 99).

Male

Not observed. According to Boucĕk (1971): body length 2.7 mm; very similar to female in body colour and structure; head and antenna hardly different, pedicel slightly longer (1.2×) than first funicular segment; stigma hardly broader than in female.

Variation

The above description is based on the type material of M. rosae . In the other female specimens we examined, body length varied from 2.1 to 3.2 mm. The specimens from southern Europe ( Bulgaria, Croatia, France) were highly variable but usually showed a thorax colour lighter than that of the type, mostly dirty yellowish with variable black to brown patches on dorsum. Lighter specimens (e.g. from the French Alps) presented a black band on anterior margin of mid-lobe of mesoscutum, a black patch on outer axilla, two black lines on metanotum, prepectus and mesepimeron being dark brown. In darker specimens (e.g. from Bulgaria), black covered anterior part of mid-lobe of mesoscutum, notula, axilla, metanotum, mesopleuron, metapleuron and propodeum. In specimens from southern Europe , forewing stigma was slightly infuscate and more elongate (1.5× as long as broad) than in type, with uncus as long as upper part of stigmal vein. The median carina on propodeum was often simple in specimens from southern Europe .

Sex ratio Boucĕk (1971) estimated it as 31:1. There were no males in our samplings.

Hosts

Develops exclusively in seeds of Rosa spp. (Rosaceae) . Recorded from R. arvensis (AR) , R. canina (Zerova and Seryogina, 1994; AR), R. ferruginea (AR) , R. pendulina (AR) , R. rubiginosa (AR) , R. tschatyrdagi and R. turkestanica (Zerova and Seryogina, 1994) , and Rosa sp. (Boucĕk, 1971; Nikol’skaya and Zerova, 1978). In Bulgaria, we observed emergences of both M. aculeatus and M. rosae from the same rose hips as did Zerova and Seryogina (1994) in Russia.

Distribution

From the southern Alps to central and southern Europe, Caucasus and Siberia: Austria (Boucĕk, 1971), Bulgaria (AR); Croatia (AR); former Czechoslovakia (Cĕrmak, 1952, as M. pictus ; Boucĕk, 1971); France (AR); Poland (MS); Russia (Siberia, AR; Crimea, the Caucasus, Tadjikistan, Turkmenistan; Nikol’skaya and Zerova, 1978; Zerova and Seryogina, 1994); Switzerland (MS).

Comments

Two other species, M. aculeatus and M. nigrovariegatus , co-exist with M. rosae in Rosa seeds of the West Palearctic. Diagnostic characters for separating the three species are given in the chapter concerning M. aculeatus .

M. rosae kondaricus Zerova and Seryogina , was identified on Rosa kokanica Regel in the Pamir Altaï mountains of Tadjikistan (Zerova and Seryogina, 1994). According to the original description, the female differs from M. rosae by a longer body (2.6–3.5mm), a wider stigma surrounded by a limited infuscated area and the absence of carina on propodeum. The male has a longer body (2.8–3.5 mm), predominantly black except light spots on vertex, around the eyes, on pronotum, on the basis of scutellum, and on axilla. Its forewing stigma is surrounded by a limited infuscated area. Sex ratio (1:1) highly differed from the one usually observed in M. rosae .

Material examined

Austria: 1 X, Wien, 1957, S. Novitzky ( BMNH) . Bulgaria: 30 X, ex. Rosa canina , Sofia, June 1994 ( AR) ; 12 X, ex. R. arvensis, Dolno Kamarci , June 1996, D. Pilarska ( AR) ; 15 X, ex. R. canina, Saranci , June 1996, D. Pilarska ( AR) . Croatia: 6 X, ex. Rosa sp. , Gruda , 24 April 1990 ( AR) . Czech Republic: 2 X, ex. R. canina, Kromerĭz , July 1992 ( AR) ; 1 X, ex. Rosa sp. , Trĕbic ˘, June 1992 ( AR) . France: 9 X, ex. R. canina, Briançon (05), elev. 1200 m, 3 April 1996 (20°C), ( AR) ; 2 X, ex. R. ferruginea, Briançon , elev. 1200 m, July 1990, ( AR) ; 8 X, ex. R. pendulina, Névache (05), elev. 1600 m, July 1994, ( AR) ; 7 X, ex. R. rubiginosa, Briançon , elev. 1200 m, 20 April 1996 (20°C) ( AR) ; 1 X, beating Rosa sp. , Brouis Pass (06), 19 July 1992, J. Y. Rasplus ( AR) . Poland: 1 X, ex. R. canina, Ojców Natl. Park , 25 May 1990 ( MS) ;

Russia: 5 X, ex. Rosa sp. , Bratsk (Siberia), June 1989, A. Chavagnat ( AR) .

Switzerland: 1 X, ex. Rosa sp. , Sion , April 1999 ( MS) .