Eurytoma strigifrons Thomson, 1876

Gómez, José Francisco, Nieves-Aldrey, José Luis, Nieves, María Hernández & Stone, Graham Nicholas, 2011, Comparative morphology and biology of terminalinstar larvae of some Eurytoma (Hymenoptera, Eurytomidae) species parasitoids of gall wasps (Hymenoptera, Cynipidae) in western Europe, Zoosystema 33 (3), pp. 287-323 : 314

Eurytoma strigifrons Thomson, 1876

MATERIAL EXAMINED. — Ex Isocolus lichtensteini : Spain. Madrid, Arganda, 6.XI.2002, J. L. Nieves leg (n = 2). — Madrid, La Marañosa, 3.XI.2004, J. L. Nieves leg (n = 3, of which 1 specimen MNHN-EY).

Ex Isocolus leuzeae : Spain. Madrid,Valgallego, 4.VIII.2002, J. L. Nieves leg (n = 1).

DESCRIPTION

n = 6; body length 1.8 mm (range 1.7-2.0); body width 1.1 mm (1.0-1.3) ( Figs 6D ; 8D ); body barrelshaped, short and wide, slightly tapering anteriorly and posteriorly; ratio L/W = 1.47; ventral margin of body segments slightly convex; anterodorsal protuberances present from second thoracic segment to the eighth abdominal and not protruding beyond the dorsal margin of body segments ( Fig. 8D ).

Antero-medial setae of antennal area slightly above the antennae; antero-medial setae of vertex situated relatively high on the upper face ( Fig. 10E ); ratios SA/LAA = 0.5 and SA/DAV = 0.9; dorsal-labral setae longer than clypeal setae; ventral margin of clypeus with a distinct suture; labrum with slight divisions limited to apical part, with undifferentiated lobes; labium and maxillary palps usually not differentiated ( Fig. 12F ).

Mandibles asymmetric, exposed in part, tip of the first tooth visible ( Fig. 12F ); right mandible with two teeth ( Fig. 13L ); left mandible with three teeth ( Fig. 13M ); first tooth of both mandibles long and slender; ratio L/W 1T = 2.25; outer margin of first tooth almost straight; tip slightly recurved; apex of the second tooth straight, directed upwards in the same direction as the first tooth, and more or less acute; inner margin of mandible, from the base of second tooth, forming a small projection close to the base of the second tooth ( Fig. 13L, M ).

BIOLOGY

Eurytoma strigifrons is an oligophagous ectoparasitoid commonly reared only from galls induced by several species of the tribe Aylacini on herbs, more commonly from galls of Isocolus species on Asteraceae ( Askew et al. 2006) ( Fig. 15E ). Claridge (1961a) recorded the species as a specific parasitoid of I. rogenhoferi , a species that induces galls in achenes of Centaurea . However we have reared it in Spain more frequently from conspicuous stem galls of I. lichtensteini on Centaurea aspera and C. melitensis ( Fig. 15E ).

REMARKS

Similar in shape to the larvae of E. robusta , larvae of E. strigifrons are readily separated from other eurytomid larvae in this study by having an almost straight, or only slightly recurved first mandible tooth.

Figures

FIG. 6.— Ventralviews of terminal-instar eurytomid larvae:A, Eurytoma rufipes Walker, 1832; B, E. sp. nr. aspila; C, E. sp. nr. jaceae; D, E. strigifrons Thomson, 1876; E, E. timaspidis (Mayr, 1904). Scale bars: 1 mm.

FIG. 8.— Lateral views of terminal-instar eurytomid larvae:A, Eurytoma rufipes Walker,1832; B, E. sp. cf. aspila; C, E. sp. cf. jaceae; D, E. strigifrons Thomson, 1876; E, E. timaspidis (Mayr, 1904). Scale bars: 1 mm.

FIG. 10. — Anterior views of the head of terminal-instar eurytomid larvae:A, Eurytoma rosae Nees,1834 ex Diplolepis rosae; B, E. rufipes Walker, 1832; C, E. sp. cf. aspila; D, E. sp. cf. jaceae; E, E. strigifrons Thomson, 1876; F, E. timaspidis (Mayr, 1904). Scale bars: A-C, 300 μm; D, 200 μm; E, F, 400 μm.

FIG. 12. — Anterior views of mouthparts of terminal-instar eurytomidae larvae:A, Eurytoma robusta Mayr,1878; B, E. rosae Nees,1834 ex Diplolepis rosae; C, E. rufipes Walker,1832;D, E.sp.cf.aspila; E, E. sp. cf. jaceae; F, E.strigifrons Thomson,1876; G, E.timaspidis (Mayr, 1904). Scale bars: A-E, 100 μm; F, G: 200 μm.

FIG. 13.— Anterior views of the right mandible of terminal-instar eurytomid larvae:A, Eurytoma aspila (Walker,1836) ex Phanacis caulicola; B, E. brunniventris Ratzeburg, 1852 ex Cynips quercus (A); C, E. cynipsea Boheman, 1836 ex Phanacis hypochoeridis; D, E. infracta Mayr, 1904; E, E. mayri Ashmead, 1887; F, E. pediaspisi Pujade i Villar, 1994; G, E. robusta Mayr, 1878; H, E. rosae Nees, 1834 ex Diplolepis rosae; I, E. rufipes Walker, 1832; J, E. sp. cf. aspila; K, E. sp. cf. jaceae; L, E. strigifrons Thomson, 1876 (right mandible); M, E. strigifrons (left mandible); N, E. timaspidis (Mayr, 1904). Scales bars: A, D-G, I-N, 50 μm; B, 20 μm; C, H, 100 μm.

FIG. 15. — A, section of a gall of Diplolepis mayri showing a fully-grown larva of Eurytoma rosae Nees, 1834; B, cross-section of Xestophanes brevitarsis (Thomson,1877) gall showing fully-grown larva of E. rufipes Walker, 1832 with host larva; C, cross-section of old gall of Aulacidea subterminalis Niblett, 1946 showing fully-grown larva of E. sp. cf. aspila; D, detail of mandibles of E. sp.cf. aspila ex gall of A. subterminalis; E, lateral view of terminal-instar larva of E. strigifrons Thomson,1876 ex gall of Isocolus lichtensteini (Mayr, 1882); F, cross-section of fresh gall of Timaspis phoenixopodos Mayr, 1882 showing fully-grown larvae of E. timaspidis (Mayr, 1904); G, larval cell of T. phoenixopodos with terminal-instar larvae of E. timaspidis.