Euura crassipes : Prous et al. 2014

crassipes subgroup

Euura arbusculae (Benson, 1941) comb. nov.

Pontania arbusculae Benson, 1941: 133 –135. Described: ♀, ♂, larva, gall, recorded host: Salix arbuscula. Holotype, ♀, BMNH [examined]. Type locality: Scotland, Killin, Crags above Lochan à Lairige. Nematus (Pontania) arbusculae: Zhelochovtsev (1988).

Eupontania arbusculae: Vikberg (2003).

Notes on types and taxonomy. P. arbusculae. Apart from the holotype, the only other known specimens of this species are the 2♀ and 2♂ paratypes, all from the type locality, BMNH [1♀, 1♂ examined].

The morphological characters given by Benson (1941), Kopelke (1989b) and Vikberg (2003) to separate adults of arbusculae from its close relatives (i.e. in northern Europe E. herbaceae and E. crassipes), are very slight, and could easily fall within the range of variability of a single species. For example, the colour characters used by Benson (1941) to distinguish arbusculae from herbaceae do not work, because the latter often also has (especially in reared specimens) a nearly completely yellow clypeus and femora. However, the shape and sculpture of the frontal area of arbusculae recorded by Vikberg (2003) appear to be reliable in distinguishing it from the other two species, although only three specimens of the arbusculae type series were available for examination. In arbusculae the frontal area is more concave, appearing deeper towards anterior, and is rather dull because of sculpture; in herbaceae and crassipes it is flatter and more shiny. The pattern of black markings of the larva may be speciesdiagnostic in this subgroup of species (Benson 1941; Kopelke 1989b), but this also needs to be checked in a larger number of specimens.

Variability. Female: Body length: 3.4–3.7mm. Male: 3.9–4.9mm. Total number of specimens examined: 3.

Genetic data. None available.

Bionomics. Host plants: Salix arbuscula (Benson 1941). Note that a further, unidentified species of the viminalis subgroup apparently uses S. arbuscula as a host (Euura sp. Salix arbuscula, larval sample from Torne Träsk Region), so that pea-shaped galls on this willow species cannot be assumed to belong to E. arbusculae. Examination of the larva should however clarify this. Biology: Benson (1941).

Distribution. The only definite record is of the type series from Scotland (Benson 1941). Galls on S. arbuscula which possibly belong to E. arbusculae have been found on Kolguyev Island, N. Russia (Zinovjev 1999). Occurrence in Sweden: may be present. Vikberg (2003) wrote "In August 1989 I found two bean-shaped galls on Salix arbuscula in the Torne Träsk area, Sweden but no larvae were found inside galls or they had been killed when small. It is possible that some other species of the group had tried this species of Salix without success".