Acasis appensata appensata ( Eversmann, 1842 )

Hausmann, Axel & Huemer, Peter, 2011, Taxonomic decision as a compromise: Acasis appensata (Eversmann, 1832) in Central Italy — a case of conflicting evidence between DNA barcode and morphology (Lepidoptera: Geometridae), Zootaxa 3070, pp. 60-68 : 61-62

Acasis appensata appensata ( Eversmann, 1842)

Acidalia appensata Eversmann, 1842: 556 .

Material examined. 233 specimens from Germany, Austria, Czech Republic, Slovakia, Byelorussia, Finland, Bulgaria, Greece, Turkey, Russia ( TLMF; ZSM).

Description. Adult ( Figs. 1–2 ). Head, thorax and tegula mixed grayish-brown, labial palpus dark brown. Wingspan 3 18–22 mm; Ƥ 20–23 mm; forewing with strongly convex termen; ground colour grey-brown, extended darker grey-brown suffusion particularly at base and along antemedian and postmedian fascia; these two fasciae distinct, light greyish with indistinct darker line; veins with short dark brown lines along outer side of antemedial and both sides of postmedial fascia; dark brown discal spot and dark brown patches along fringe line well developed; fringes chequered greyish-brown, outer part lighter. Hindwing grey-brown with lighter postmedial fascia; small discal spot; darker grey terminal line and weakly chequered fringe; base of anal area in male with short lobe. The extent of dark suffusion of the forewing underlies some variation. Male genitalia ( Figs. 7–8 ). Uncus broad, sub-triangular, apically pointed; valva sub-oval, with rounded apex; sacculus strongly sclerotized, shorter than valva, basal part broad, distally tapering but rounded; costa with spiny sub-basal hump, cucullus separate, slender and slightly club-shaped, projecting far above apex of valva; saccus short, broad, horseshoe-shaped; lateral lobes of transtilla covered with short bristles; aedeagus moderately long and slender, weakly curved, without cornuti. Female genitalia ( Fig. 15 ). Papillae anales well developed; apophyses posteriores about two times length of tergum A8; tergum A8 smoothly sclerotized, without modifications; apophyses anteriores comparatively long and rod-like, about half length of tergum A8; antrum (colliculum) tubular, posteriorly funnel-shaped, length (0.3-0.4 mm) about that of apophyses anteriores, sub-genital plate (sterigma) largely reduced; ductus bursae extremely short and without distinct transition to corpus bursae; corpus bursae evenly dilated to sub-oval distal part with a large spinulose patch in diffuse ring shaped position; appendix bursae present. Posterior part of corpus bursae with longitudinal furrows.

Diagnosis. Acasis appensata appensata is a rather invariable taxon with a grey-brown ground colour and distinctly lighter ante- and postmedian fasciae. The ground colour is of particular diagnostic value compared to the other European species A. viretata which exhibits an extended yellowish-green to brownish-green colour ( Figs. 5– 6 ), and to the pale green A. appensata callaina ssp. nov. ( Figs. 3–4 ) (see below). A. appensata furthermore differs from A. viretata by several characters of the male and female genitalia ( Figs. 13–14 , 18 ). In the male the broad uncus, the long cucullus which overtops the apex of the valva, the spiny sub-basal hump of the costa, the short sacculus and the lateral lobes of the transtilla with short bristles are characteristic. In the female the long and narrow, funnel-shaped antrum, the largely reduced sub-genitalia plate and furthermore the anteriolateral margin of tergum VIII which is weakly projected anteriad and the long apophysis anterioris are specific characters.

Bionomics. The larva of the nominotypical subspecies has been recorded feeding on unripe and also on ripe fruits which are loosely spun together, or on the leaves of Actaea spicata ( Burmann 1955; Skou 1986), according to Skou (1986) also on Veronica longifolia . Feeding habits depend on the phenology of the host-plant which shows much variation, and on the geographic region ( Burmann 1955). In northern Europe the species feeds on various other plants, e.g. Valeriana sambucifolia , Actaea erythrocarpa ( Mutanen et al. 2003; Mutanen pers. comm.). The larval period lasts from mid-June to late July. Pupation takes place in weak cocoon on the ground surface and the pupa hibernates. Adults have been observed from mid-May until mid-June, in the northern part of the range throughout the entire month of June ( Skou 1986). Whereas larvae are frequently found, the adults are rarely observed. Characteristic habitats are clearings in deciduous and mixed forests, particularly beech forest. The species occurs from lowland habitats up to about 1200 m above sea-level in the Alps.

Distribution. Vast range from Europe to the Urals, Siberia, Amur and Ussuri regions and Japan. In Europe occurring mainly in the Alps and adjacent areas and from Fennoscandia to central Urals. In northern Europe also on coastal meadows and deciduous forests and meadows along riversides ( Mutanen et al. 2003; Mutanen pers. comm.). Absent from large parts of the Balkans, the Iberian Peninsula and from all Mediterranean lowlands and islands.

Remarks. The taxonomic status of the taxon baikalensis (original combination: Lobophora appensata v. baikalensis ) needs further investigation. According to the original description it differs from Central European A. appensata by the dark blackish-grey ground colour and the on average smaller wingspan ( Bang-Haas 1906). Following Scoble (1999) this taxon is considered as a synonym of nominotypical A. appensata .

Figures

FIGURES 1 – 6. Adults of Acasis. 1 – 2, A. appensata appensata (Eversmann); 3 – 4, A. appensata callaina ssp. nov.; 5 – 6, A. viretata (Hübner).

FIGURES 7 – 14. Male genitalia of Acasis. 7 – 8, A. appensata appensata (Eversmann), slide G 1460; 9 – 10, A. appensata callaina ssp. nov., paratype, slide G 1464; 11 – 12, ditto, paratype, slide G 1461; 13 – 14, A. viretata (Hübner), slide G 1462.

FIGURES 15 – 18. Female genitalia of Acasis. 15, A. appensata appensata (Eversmann), slide G 1459; 16, A. appensata callaina ssp. nov., paratype, slide G 1456; 17, ditto, paratype, slide G 1458; 18, A. viretata (Hübner), slide G 1463.