Ormyrus nitidulus (Fabricius, 1804)

Gomez, Jose F., Nieves, Maria Hernandez, Gayubo, Severiano F. & Nieves-Aldrey, Jose Luis, 2017, Terminal-instar larval systematics and biology of west European species of Ormyridae associated with insect galls (Hymenoptera, Chalcidoidea), ZooKeys 644, pp. 51-88 : 63

Ormyrus nitidulus (Fabricius, 1804)

Material examined.

ex gall Andricus hispanicus on Quercus canariensis , Spain, Málaga: Algatocín, 19.VIII.02, J. L. Nieves leg (n = 1); ex gall Andricus hispanicus on Quercus faginea , Spain, Salamanca: Laguna de San Marcos, 26.VIII.03, J. L. Nieves leg (n = 1)

Description.

n = 2; Body length: 4.28 ± 0.87 mm (min-max: 3.67-4.90 mm), width: 2.13 ± 0.18 mm (min-max: 2.00-2.25 mm).

The larva of this species is the largest among all the European species. Is quite similar in most diagnostic characters to the larvae of the related species Ormyrus pomaceus , being differentiated by its large size and the blister like sculpture much less conspicuous. Other diagnostic characters are as follows: body short and wide, not tapering towards the anal segment. Setae of thoracic segments shorter than ½ length of a thoracic segment; ratio AC/AV 0.77, the shortest among all the studied species (Table 2); anteromedial seatae of antennal area short, 0.3 as long as distance among antennae; lcs separated from cs 0.7 times the distance between cs; maxillary palps conspicuous (Figs 3E, 5E, 7E; Table 2).

Biology.

The species Ormyrus nitidulus is a member, with the closely allied Ormyrus pomaceus , of the parasitoid community associated with oak gall wasps ( Hymenoptera , Cynipini ). The two species were reared from more than 50 different species of cynipids associated with Quercus species in the west Palaearctic ( Askew et al. 2013); however, Ormyrus nitidulus is not as common and is less polyphagous than Ormyrus pomaceus . In contrast to the closely related species Ormyrus pomaceus , Ormyrus nitidulus prefers to attack the large galls of asexual generations of heteroecic species of Andricus . On the Iberian Peninsula, Ormyrus nitidulus was reared primarily from galls of Andricus hispanicus (Fig. 13D, E, and F) and the asexual generation of Andricus grossulariae . Our observations of dissected galls showed the larva of Ormyrus nitidulus was a primary ectoparasitoid of the galling inducer. In the host galls of Andricus hispanicus , the larvae always occupied the host central larval chamber, not the secondary cells occupied by inquilines.