Euura proxima (Serville, 1823)

Liston, Andrew D., Heibo, Erik, Prous, Marko, Vårdal, Hege, Nyman, Tommi & Vikberg, Veli, 2017, North European gall-inducing Euura sawflies (Hymenoptera, Tenthredinidae, Nematinae), Zootaxa 4302 (1), pp. 1-115 : 83

E. proxima group

= Pontania Costa, 1852 , in part

Diagnosis. Adult. In lateral view right mandible gradually tapering, left one with swollen base and thin, blade-like apex. Vein 2r-m normally present in both fore wings. Supraclypeal area entirely glabrous, or with at most 1–5 setae. Antenna moderately long: ♀ about as long, or slightly longer, than costa of fore wing; ♂ longer than costa of fore wing. Cercus short: about 3× as long as maximal width and reaching back only to about middle of valvula 3. Medial and basal annuli with flat ventral edge (serrulae not clearly developed). Antennal hollow nearly entirely glabrous and shiny. Penis valve: ventrally with small spines; base of valvispina ventrally clearly divided from lobe on which it arises by an incision or at least a right-angled turn.

Larva. Third abdominal segment with 4 dorsal annulets. Suranal plate with widely separated pseudocerci.

Gall. In leaves. Rather flat; "coffee bean" shaped. Developed only above the leaf-blade, or projecting on both sides. Not usually touching midrib.

Phenology. Usually bivoltine, or even trivoltine, depending on climatic conditions.

Notes. Compared to other gall-inducing Euura , species of this group exhibit some unusual biological traits. Unlike nearly all other West Palaearctic species, they reproduce by thelytokous parthenogenesis ( Carleton 1939, Kopelke 2005). Males have occasionally been obtained in large scale rearings, at a ratio of one to several hundreds, and are therefore likely to be rare in nature. On the other hand, Carleton (1939: 592) pointed out that the number of males could be underestimated in rearings, if the males leave their galls earlier than females and galls are picked shortly before they mature. If, however, thelytoky is accepted as normal in the European members of this group, then the conventional tests of species limits are difficult to apply, e.g. there is no possibility of attempting to mate opposite sexes of different segregates. Larvae in the fourth, or sometimes an earlier instar, make a hole in the gall, usually on its underside, through which they eject the excrement. The larvae sometimes temporarily leave the gall through this hole to feed externally on the leaf-blade ( Kopelke 1999). Further, whereas all but a few species in other species groups are univoltine, members of the proxima group are bi- or even trivoltine at localities where the growing season is sufficiently long. Zinovjev (1999) noted that the host specificity of some sawflies in this group is not as narrow as is the rule in, for example, the viminalis group: E. bridgmanii is recorded from numerous species in various sections of Salix subgenus Vetrix .