Cerroneuroterus minutulus (Giraud, 1859)

Neuroterus minutulus Giraud, 1859

Cynips minutulus (Giraud) Kaltenbach, 1867 (only gall)

Spathegaster (Ameristus) aggregata Wachtl, 1880 syn. nov.

Neuroterus minutulus (Giraud) Kieffer, 1901

Neuroterus aggregatus (Wachtl) Mayr, 1882

Cerroneuroterus minutulus (Giraud) Melika et al., 2010

Cerroneuroterus aggregatus (Wachtl) Melika et al., 2010

Asexual galls (Figs 1–8). Asexual galls develop on the underside of the leaf blade (Figs 1–3) (sometimes also on the upper side), have a slightly elliptical subglobular shape and are very small, reaching at most 1.5–2.0 mm in diameter when mature. Their external surface is glabrous, covered with short and more or less pointed cone-shaped tubercles uniformly arranged in a regular pattern (Figs 4–6). They are attached to the leaf by a thin, short stalk (Fig. 7), rarely on the veins and the leaf does not show any mark on the opposite surafce indicating a gall is present beneath. Each leaf can contain up to ten galls.

The growing galls are a greenish colour with very pronounced coniform protrusions, subsequently turning reddish-yellow shades and then slightly brown when mature at which point the protrusions become less pronounced. The galls are unilocular and the larva (Fig. 8), feeding on the whitish nutritive tissue, creates a large chamber in which it spends a long diapause protected by strong, leathery walls. Galls are not deciduous but fall with the leaves into the litter where the larvae complete their metamorphosis.

Sexual galls (Figs 9–15). The sexual galls develop on adventitious buds mainly on large oak trunks (Fig. 9–10), often in groups of 5–12, sometimes solitary; they are unilocular (Fig. 11), sessile, sub-ellipsoidal in shape (ovoid) with major axis length 2.0– 2.3 mm, minor axis 1.8–2.1 mm. During the short growing phase, they have a succulent texture, with conspicuous red, purple and light green colouration (Figs 10–12); their surface is granular, owing to the presence of a layer of large protruding cells (Fig. 14), the walls often adorned with thin lamellae, vestiges of the transformed bud perulae (Fig. 12); as they mature, the granulation is reduced by dehydration and the surface takes on a light brown colour and the walls become thin and coriaceous (Figs 13–14). Sexual adults emerge from a large lateral hole and the galls are not deciduous and remain attached to the bark for a few years. Fresh galls obtained in this study were compared with those that were collected by Gaicomo Mantero in 1909 in Liguria (Genoa province) preserved in ‘Cecidotheca italica’at the Botanical Garden of Padua (Fig. 15) (see “Additional material examined for morphological diagnosis”); both sets of gall were identical .