THE IDENTITY OF THE GALL-WASP CAUSING STUNTED ACORNS (HYMENOPTERA, CYNIPIDAE) by A. A. WIEBES-RIJKS (Division of Systematicsand EvolutionaryZoology, University of Leiden, The Netherlands) SUMMARY Description of the agamous female of Andricus legitimus spec. nov., causing mono- thalamous galls in stunted acorns of European Quercusrobur L. Records of inquilines and parasites from polythalamous galls: Synergusclandestinus Eady, S. gallaepomiformis (Fonsc.) (Cynipidae); Megastigmus dorsalis (F.) (Torymidae) and Eurytoma brunni- ventris Ratz. (Eurytomidae). According to BUHR (1965: 966), there occur two galls in stunted acorns of European oaks. The one is monothalamous (no. 5535), having one chamber per gall, situated in between the hardened cotyledons. The gall-wasp causing it remained unknown, although MAYR described the gall as early as 1872. The other gall is poly- thalamous (no. 5536), with up to nine chambers. It was supposed to be caused by a species of Callirhytis related to C. glandium (Giraud), known from the acorns of Quercus cerris L. From the acorns of Quercus robur L., specimens of Synergus clandestinus Eady were reared in great numbers and recently it was suggested that this species caused the gall. It now appears that the monothalamous form is the original gall caused by Andricus legitimus spec. nov. The polythalamous gall is due to the secondary gall-forming influence of the inquilinous Synergus clandestinus Eady. In rare instances, Synergus gallaepomiformis (Fonsc.) and two parasites of S'ynergus, viz., Megastigmus dorsalis (F.) and Eurytoma brunniventris Ratz. are reared from stunted acorns. All material mentioned is preserved in the Rijksmuseum van Na- tuurlijke Historie, Leiden. THE GALL-CAUSER Andricus legitimus spec. nov. Figs. 1-10, 13; Pl. I figs. A-B, Pl. II figs. A, C-D. In the following list of records, all references are cited that can be recognised as belonging to the (in some instances, parasitised) gall of Andricus legitimus. 244 Andricusglandium (Giraud) [misidentification], du Buysson, 1900: 357 (between Chinon & Loudon, Indre-et-Loire, France, stunted acorns of Quercus pubescens) ; Connold, 1908: 60, pl. IX div. A (Hollington & St. Leonards, E. Sussex, England, Quercus pedunculata)[evidently parasitised]. Callirhytis ("aff.") glandium Giraud [misidentification], Houard, 1908: 211, fig. 256d (no locality, France, Quercus robur) [evidently parasitised] ; Buhr, 1939: 59 (Friedland, Neu-Brandenburg, East-Germany, Quercuspedunculata) ;Baudyš, 1954: 104 (Libotin near Stramberg, Moravia, Czechoslovakia, Quercusrobur) ;PfJtzenreiter & Weidner, 1958: 125 (Favoritepark near Ludwigsburg, Württemberg, West- Germany, Quercus robur) [evidently parasitised] ; Buhr, 1965: 966 (no locality, Germany, nos. 5535-6, i.a., Quercusrobur). "Stunted accorn", Mayr, 1872 : 699 (no locality; Synergusevanescens) von ; Schlech- tendal, 1891 : 21 (no locality, Germany, no. 193, i.a., Quercusrobur) ; Pigeot, 1904 (Ardennes, France) ; Houard, 1908: 211, fig. 257e (no locality, France, Quercus robur) ; von Dalla Torre & Kieffer, 1910: 770 (no locality, i.a., Quercus petrea) ; Forsius, 1927: 5-6 (Skaldo near Ekenäs & Näversholm, Finland, "Galle Forsius 5", Quercusrobur; also parasitised acorns: Synergusevanescens); Niblett, 1945: 72 (Berk- hampstead Common, Herts., England, Quercusrobur, parasitised by Synergusevanes- cens) ; Benson, 1946: 46 (same record as Niblett) ; Eady, 1952 : 148 (specimens of Niblett & Benson: Synergusclandestinus) ;Docters van Leeuwen, 1957: 221, fig. 804 (no locality, The Netherlands, Quercus robur; Synergusevanescens suggested as gall- causer) ; Eady & Quinlan, 1963: 27, 64, fig. 282 (no locality, England, Quercusrobur; Synergusclandestinus); Gauss, 1972: 340-342 and 1972a: 577-578 (between Baden- weiler & Kandern, Sidbaden & Kandel-Hagenbach-Schaidt, Rheinland-Pfalz, West-Germany; Synergusclandestinus suggested as gall-causer); Wiebes-Rijks, 1979: 314 (no locality, The Netherlands, Quercusrobur ;Synergus gallaepomiformis). Description.-Agamous female (Pl. II fig. A). Length of head, thorax and gaster in stretched condition 4.5-5 mm. Body reddish, marked with black around the mouth and the antennal toruli, on the terminal segments of the palps, the mid part of the pronotum, two longitudinal patches on the mesoscutum, the fovea of the scutellum, the propodeum and in the middle of the mesopleurae. The antenna from the pedicel onwards, the trochanter, coxa and tarsi of the legs, and the veins of the wings are dark brown to black. Head. Viewed from above (fig. 2), the width of the head across the temples is three times the length, the temples are dilated behind the eyes. In frontal aspect, the length is three-fifths of the width. Surface finely coriaceous, weakly pubescent between the toruli and the clypeus and along the cheeks. Antenna (fig. 6) 15-segmented; the second to fifth segments approximately in ratio 9 :23 :17 : 14, the 12-14th seg- ments times as long as wide. Mouthparts : the maxillary palps con- sisting of four segments, the labial palps of three. Thorax. Mesoscutum almost smooth and shiny, with sparse setae in the anterior part, along the lateral borders and the parapsidal grooves. Notaulices distinct over the whole length. The lateral lines are in- distinct and do not reach to the posterior edge of the mesoscutum. Median scutal line absent or indistinct, then consisting of one or two .