Eurytoma striolata, RATZEBURG, 1848

Delvare, Gérard, Gebiola, Marco, Zeiri, Asma & Garonna, A. P., 2014, Revision and phylogeny of the European species of the Eurytoma morio species group (Hymenoptera: Eurytomidae), parasitoids of bark and wood boring beetles, Zoological Journal of the Linnean Society 171 (2), pp. 370-421 : 407-411

EURYTOMA STRIOLATA RATZEBURG, 1848

( FIGS 27A–H , 28A–C , 29E–H , 32J–O , 33D–I , 34J–L , 35A–F )

Eurytoma striolata Ratzeburg, 1848: 177 . Original description.

Host: Scolytus (= Eccoptogaster ) intricatus (Ratzeburg, 1837) .

Euritoma Masii Russo, 1925: 76–84 . Original description. Italia: Sicilia.

Hosts: Chaetoptelius vestitus (Mulsant & Rey, 1860) , Scolytus (= Eccoptogaster ) amygdali Guerin, 1847 , Hylesinus toranio (Danthoine, 1788) (= oleiperda Fabricius), Phloeotribus scarabaeoides Bernard. Host plants: Pistacia , Olea europaea .

= Eurytoma morio Boheman : Szelényi, 1976: 175 (Erroneous synonymy).

Eurytoma kemalpasensis Narendran, Tezcan & Civelek, 1995: 84 . Original description. Turkey.

Host: Scolytus rugulosus (Müller, 1818) .

= Eurytoma kemalpasensis Narendran, Tezcan & Civelek, 1995 syn. nov.

Type material

Eurytoma striolata . None. The Ratzeburg collection was destroyed and all types lost. The original description just quotes: ‘Length 1.8 mm. Very similar to the previous species (= E. aciculata ) but propodeum with broad and shallow trough in centre, which has not the rough sculpture of the other ones but is finely transversely striolate. Gaster relatively long and acute and with ovipositor exerted for 1/8 of gaster length’ (translated from German). The mention of Scolytus intricatus (= oak bark beetle) suggests that E. striolata parasitizes beetles infesting deciduous trees. ‘Hr. Nördlinger’ (= Hermann Nördlinger) evidently published the book ‘Essai sur les formations géologiques des environs de Grand-Jouan, près Nozay Loire-Inférieure’ in 1847 and ‘Mémoire sur les essences forestières de la Bretagne’ in 1845. This helps us to situate Grand-Jouan in the region Paysde-la-Loire, France, and department Loire-Atlantique, and confirms that Nördlinger did work on forest insects. Eurytoma kemalpasensis . Holotype ♀ (in QMBA). For labelling, see Figure 9I . Eurytoma masii . Lectotype ♀, here designated, glued on the top rectangular card of a series that includes two other males, most probably conspecific with this female and labelled ‘ Eurytoma Masii Russo Typi ♀ ♂ ’ (handwriting) (in MES) . The male on the medium card is obscured by glue; it seems to belong to the minor form of E. striolata . The female shows the distinctive characters of the species.

Remarks

The comparison with E. aciculata suggests specimens of small size, with black legs and scape. Furthermore, the description of the propodeum and gaster is in accordance with the series of small specimens of E. melanoneura or E. kemalpasensis . The minor forms of these latter species have darker appendices, the gaster is more elongate than in the major forms, with the ovipositor occasionally somewhat exerted; the description of the propodeum is also in agreement ( Figs 26G , 35B, D ). The choice between the two names was made in accordance with the type locality. We had sequenced specimens of E. melanoneura from the UK, from where the species was described. Our sampling included a few specimens similar to E. kemalpasensis from the same region as where E. striolata was described. Therefore, we assigned these specimens to E. striolata .

Eurytoma masii was synonymized with E. morio by Szelényi (1976). It is here removed from this synonymy and instead synonymized with E. striolata , showing all the distinctive characters of the species (see below).

Variation

Major form ( Figs 27A–H , 28A–C , 29E–H , 32J–L , 34D– F , 35A, B, E, F ). Size 3.15–3.75 mm. Lateral panel of

pronotum, pro- and mesocoxae, acropleuron, edge of oral fossa and subantennal stripe dark. Scape and fore tibia at least partly, sometimes entirely, testaceous. Head transverse in dorsal view, 1.80–1.90 times as wide as long. Malar space about 0.70–0.75 times height of eyes. Outline of genae straight. Clypeus deeply emarginate. Lower face mostly punctured with short radiating ridges. Setation dense and thick. Gena almost completely punctured. Vertex punctured as well. All funicular segments longer than wide, fusiform, decreasing in length, bearing numerous MPS. Clava broadly rounded apically. Notauli appearing as impressed lines, not obliterated by the sculpture of the mesoscutum. Median channel of propodeum incompletely delimited, the bottom with dull, coriaceous sculpture, median ridge incomplete and irregular. Metacoxa densely setose dorsally from base. Lower surface of costal cell completely setose, bearing numerous short and white setae. Marginal vein somewhat to evidently thickened, 3.50–4.00 times as long as wide. Membrane hyaline below marginal vein. Petiole rather long, with complete mediodorsal ridge. Gaster shorter than that of E. morio . Ovipositor ascending slightly. Syntergum shorter than GT6 on median line.

Male. Body with extensive yellow parts, at least on ventral side. Ventral swelling of scape vestigial, bearing only a few pores (visible on slide-mountings). Funicular segments virtually linear, F1–F2 hardly asymmetric, F3–F4 with very short apical peduncles, F5 truncate at apex. Median channel of propodeum clearly distinct, with complete median ridge, surface on bottom of areoles smooth. Forewing similar to that of the female. Minor form ( Figs 32M–O , 33G–I , 35C, D )

Size 1.65–2.15 mm. Scape and fore tibia mostly dark, sometimes entirely so. Head long and globose in dorsal view, 1.55 times as wide as long. Head subcircular in frontal view, with outline of genae evidently convex. Clypeus moderately emarginate. Sculpture of lower face and frons punctured–striolate, superficial. Setation sparse and thin. Malar space only 0.65 times as long as height of eyes, which are larger than in the major form. Pro- and mesonotum with punctures as large as in the major form, hence much less numerous according to the reduced size of the mesosoma. Median channel of propodeum incompletely delimited, but surface smooth on the bottom of the numerous secondary areolae. Apical setation reduced together with that on the metacoxa. Costal cell less densely setose than in the major form. Gaster relatively long and slender. Male antenna with the same pattern as in the previous form, but with shorter funicular segments.

Another form isolated in our initial sorting has a distinct apicoventral swelling on the scape of the female that bears several pores ( Fig. 27D ). It occurs both in the major and the minor forms. It was not correlated with any genetic variation. At last a few specimens belonging either to E. striolata or to E. melanoneura exhibited a dorsoventrally compressed body with a flat mesonotum. This phenotypic variation in size and shape was not linked with any genetic divergence in our molecular data. We have observed similar variation in other parasitoids of xylophagous beetles belonging to Pteromalidae , Braconidae , or Stephanidae .

Hosts

The specimens collected were mostly found on deciduous dying trees or logs. A large series including all forms was reared from Phloeotribus scarabaeoides on the olive tree or on Fraxinus excelsior . The Russo collection also includes numerous specimens from the same host. The specimens sequenced were reared from Scolytus amygdali Guérin, 1847 on Prunus amygdalus Batsch and from Orthotomicus erosus (Wollaston, 1857) on Pinus pinea . The type of E. striolata was reared from Scolytus intricatus and the types of E. kemalpasensis was reared from Scolytus rugulosus . As E. striolata was previously mixed with E. morio it is not possible to consider the data from the literature until the relevant voucher specimens are examined.

Distribution

Our sample comprised specimens from a wide geographic range, from France, including Corsica, to Italy and Tunisia. Eurytoma kemalpasensis was described from Turkey. Undoubtedly the species is widely distributed and common.

Figures

Figure 9. A–I, labelling of some types. A, lectotype ♀ of Eurytoma arctica Thomson, 1875; B, lectotype ♀ of Eurytoma umbilicata Thomson, 1876; C, holotype ♀ of Eurytoma blastophagi Hedqvist, 1963; D, holotype ♀ of Eurytoma fraxinicola Hedqvist, 1963; E, paratype ♀ of Eurytoma annilai Hedqvist, 1974; F, holotype ♀ of Eurytoma kangasi Hedqvist, 1966; G, paratype ♀ of Eurytoma kangasi Hedqvist, 1966; H, allotype ♂ of Eurytoma kangasi Hedqvist, 1966; I, holotype ♀ of Eurytoma kemalpasensis Narendran, Tezcan & Civelek, 1995.

Figure 26. A–D, Eurytoma saliphila sp. nov. (paratype ♂): A, mesopleuron in anterolateral view; B, propodeum; C, scape; D, antenna.

Figure 27. A–H, Eurytoma striolata (♀ major form): A, head in dorsal view; B, antenna; C, scape; D, scape (phenotypic variation); E, mesosoma in dorsal view; F, mesosoma in lateral view; G, propodeum; H, gaster in lateral view.

Figure 28. A–C, Eurytoma striolata (♂ major form): A, head in frontal view; B, propodeum; C, antenna.

Figure 29. A–H, comparison between Eurytoma melanoneura and Eurytoma striolata (♀ major forms): A–D, E. melanoneura; E–H, E. striolata. A, E, base of forewing; B, F, same, wing tilted to see the bare posterior stripe of the basal cell; C, G, detail of setation of the costal cell; D, H, apical venation.

Figure 32. A–O, SEM images of female Eurytoma heads in frontal view: A–C, Eurytoma laricis; D–F, Eurytoma aloisifilippoi; G–I, Eurytoma morio; J–L, Eurytoma striolata (major form); M–O, Eurytoma striolata (minor form). A, D, G, J, M, head; B, E, H, K, N, lower face; C, F, I, L, O, clypeus.

Figure 33. A–I, SEM images of male Eurytoma heads in frontal view: A–C, Eurytoma morio; D–F, Eurytoma striolata (major form); G–I, Eurytoma striolata (minor form). A, D, G, head; B, E, H, lower face; C, F, I, clypeus.

Figure 34. A–L, SEM images of male Eurytoma antennae: A–C, Eurytoma laricis; D–F, Eurytoma annilai; G–I, Eurytoma morio; J–L, Eurytoma striolata (major form). A, D, G, J, antenna; B, E, H, K, pedicel and F1; C, F, I, L, scape.

Figure 35. A–F, SEM images of Eurytoma striolata: A, B, F, female of major form; C, D, female of minor form; E, male of major form; A, C, pronotum and mesoscutum; B, D, E, propodeum; F, petiole in dorsal view.