Amphibolips magnigalla sp. nov.

Regarding the gall, the new species is easily distinguished by its large spindle-shaped gall (approximately 10 cm in length × 2.5 cm in diameter), which is at least 2× larger than any other spindle-shaped gall described from Mexico. Amphibolips fusus and A. durangensis induce galls morphologically similar to the gall of the new species. However, besides the differences in size, the inner structure of the gall induced by the referenced species is different, being filled with a dense soft tissue, while the inner structure of the gall induced by the new species is often almost empty, with visible radiating filaments from the central larval cell.

Gall (Fig. 5A–D). A large spindle-shaped gall with an elongated and narrow tip and base. The galls measure 100 × 25 mm on average. The surface of the gall is smooth, but some superficial longitudinal ridges are visible. The gall is monothalamic; the outer shell is thin, flexible and of fleshy consistency when it is fresh and becomes soft and light when it dries. They are light green without spots when they are fresh and light brown when they are dry. Internally (Fig. 5C), there is an oval larval cell in the centre of the gall (0.35 mm thick and 7 × 5 mm; n = 1). A spongy tissue occupies the entire space between the epidermis and the larval chamber, the outer shell is weakly attached to the internal spongy tissue when fresh and when the gall dries, the spongy tissue allows us to observe the radiant filaments, which extend from the larval chamber towards the internal walls of the galls (Fig. 5D). When it is dry, the gall is very fragile and can be easily crushed. At least half of the galls no longer showed spongy tissue when they were transferred to the laboratory. This caused the galls to collapse due to the fragility of the epidermis. Some of these collapsed galls presented internal modifications in the epidermis, probably caused by inquilines.

The galls develop on twigs of Quercus zempoaltepecana Trel. The gall closely resembles that of Amphibolips durangensis Nieves-Aldrey & Maldonado, 2012. However, the gall of A. magnigalla is distinguished by its larger size, which is at least 2× longer than that of A. durangensis and by its different internal structure, which is filled with less dense spongy tissue and radiant filaments (easily visible in the older galls).

Distribution: A. magnigalla was found only in one site: Comaltepec (Oaxaca State, Mexico). The galls were relatively abundant on a single isolated tree, while we did not find galls on the nearby trees.

Biology Sexual generation. The galls were collected at the end of April and the insects emerged shortly thereafter, in early May. It seems that it is normal for many insects to feed on the tissue of this species. A detached gall was observed in a field, relatively far from the tree, probably carried by a bird.