Acoenonia baltica Jaschhof, 2017, sp. nov.

Acoenonia baltica sp. nov.

Fig. 9A–E

This species was illustrated by Meyer and Spungis (1994: fig. 1) under the name Acoenonia parvolobata Mamaev & Berest on the basis of a specimen from Latvia (Voldemars Spungis, in litt.).

Diagnosis. Acoenonia baltica, a typical representative of the genus Acoenonia (Jaschhof & Jaschhof 2009: 88), is distinguished by male genitalic characters, as follows. The ejaculatory apodeme has a subtriangular apical widening that bears about 15 small spines; the apical third of the apodeme is covered by a large membranous cap decorated with small triangular spines (Fig. 9A). The tegmen is blunt-ended (Fig. 9A). The elongate, unlobed gonostylus has a narrow, glabrous, dorsal border along its full length (Fig. 9A–B). The female of this species remains unknown.

Differential diagnosis. In Acoenonia europaea, a species resembling A. baltica, the apical widening of the ejaculatory apodeme is larger and provided with innumerable small spines; the tegminal apex is rounded; and the gonostylus has a broadly rounded lobe dorsobasally (Jaschhof 1998: fig. 43b, d).

Other male characters. Body size 1.1 mm. Head. Eye-bridge borderless laterally, 4–5 ommatidia long dorsally. Flagellomeres 11, neck of fourth flagellomere slightly shorter than node (Fig. 9C). Palpus with 3 segments, only basal segment with translucent sensilla (Fig. 9D). Wing membrane with very few setae apically. Terminalia (Fig. 9A). Gonocoxites with moderately deep V-shaped emargination ventrally, dorsal apodemes short, protrude slightly beyond ventrobasal gonocoxal margin, dorsal bridge concave. Gonostylus 2.5 times longer than wide. Tegmen suddenly narrowed on apical third. Ejaculatory apodeme compressed and extended basally.

Etymology. The species epithet, baltica, is an adjective derived from mare balticum, the Latin name of the Baltic Sea.

Types. Holotype. Male (no. CEC376), Sweden, Öland, Borgholm, Horns kungsgård Nature Reserve, mixed forest of birch, alder and willow trees at lakeside, 21 July–22 Aug. 2015, Malaise trap, M. & C. Jaschhof (in NHRS). Paratype. Male (no. CEC377), same data as the holotype (in SDEI).

Distribution and phenology. Sweden (Öland), Latvia. This species is known only from a very few specimens, despite year-long collecting of Micromyinae in both Sweden and Latvia. Specimens were obtained in summer from broadleaf forests.