New record of the lace bug species Acalypta marginata (Wolff) (Hemiptera: Heteroptera: Tingidae) from Japan

Abstract Background The lace bug species Acalypta marginata (Wolff, 1804) has, to date, been widely known to occur in the Palaearctic Region, but has not been recorded from Japan. New information Acalypta marginata is recorded from Japan for the first time. Its habitat in Japan is the grassland of Hokkaido. A key to the species of Acalypta occurring in Japan is provided.


Introduction
The lace bug species Acalypta marginata (Wolff, 1804) (Hemiptera: Heteroptera: Tingidae) is widely distributed in the Palaearctic Region (Péricart andGolub 1996, Aukema et al. 2013). In eastern Asia, this lace bug has been known to occur in Korea and Mongolia to date (Golub 1982, Cho et al. 2020.
Recently, I sorted a collection of Heteroptera from Hokkaido, Japan and found an undetermined species of Acalypta. After careful morphological examination, I concluded that the undetermined species represents A. marginata. Here, I report A. marginata from Japan for the first time. Additionally, I provide a key to Acalypta species occurring in Japan.

Materials and methods
Dried specimens were used. Morphological characteristics were observed under a stereoscopic microscope (SZ60, Olympus, Tokyo, Japan). Specimens were photographed using a digital microscope (VHX-1100, Keyence, Osaka, Japan). Distribution records of species were mapped using SimpleMappr (Shorthouse 2010). Geographical coordinates were obtained from Google Maps. The terminology used in this study generally follows that of Drake and Ruhoff (1965). All the specimens used in this study were deposited at the Laboratory of Entomology, Faculty of Agriculture, Tokyo University of Agriculture, Kanagawa, Japan (TUA).

Diagnosis
Acalypta marginata can be differentiated from other species of Acalypta by a combination of the following characteristics: both macropterous and brachypterous morphs known; body fuscous, elongate in brachypterous morph (Fig. 1a, b) and oblong in macropterous morph; antenniferous tubercles obtuse, slightly curved inwards; basal part of antennal segment III not thickened; rostrum reaching posterior margin of metasternum (Fig. 1c); pronotum tricarinate, 0.8 times as long as maximum width across paranota; hood concealing basal eighth of vertex; pronotal carinae laminate; calli coarsely punctate; paranotum with 2 rows of areolae at widest part; anterolateral angle of paranotum rounded, not protruding anteriad; posterolateral angle of paranotum not protruding posteriad; posterior process 2.2 times as wide as its length; posterior margin of hemelytron in brachypterous morph weakly sinuate; gap between both hemelytra in brachypterous morph distinctly narrower than discoidal area at widest part of each; costal area with a single row of areolae throughout its length; subcostal area with 3-5 rows of areolae at widest part; discoidal area with 3-5 rows at widest part, expanded beyond apical fourth of hemelytron in brachypterous morph, as wide as subcostal area at widest parts of each; and basal third of discoidal-sutural boundary vein carinate.

Biology
The host plant for Acalypta marginata in Japan is unknown. In other distribution areas, A. marginata is found on Rhytidiadelphus sp. (Hylocomiaceae); it is also found on herbaceous plants (Putshkov 1974, Péricart 1983, Rédei et al. 2004, Rintala and Rinne 2011. Acalypta marginata is found in grasslands in Japan. In other distribution areas, A. marginata is known to be found in dry and sunny environments, such as grassy ground; however, it is sometimes collected from humid and shaded environments, such as the forest floor (cf. Putshkov 1974, Rédei et al. 2004).
In Japan, adults have been collected only in July and the overwintering stage is unknown. In other distribution areas, adults are found in almost all seasons and the overwintering stage is known to be the adult or elder nymph (Putshkov 1974, Péricart 1983, Rédei et al. 2004, Rintala and Rinne 2011.

Taxon discussion
The above-recorded specimens match well with the photographs of the non-types (Rintala and Rinne 2011), descriptions (Wolff 1804, Péricart andGolub 1996) and keys (Putshkov 1974, Golub 1988 of Acalypta marginata described from Hungary, based on the brachypterous morph. Collection sites for Acalypta marginata from Hokkaido, Japan.
New record of the lace bug species Acalypta marginata (Wolff) (Hemiptera: ... Acalypta marginata is very similar to A. nigrina Fallén, 1807 in the shape of the antenniferous tubercles and the pronotum; however, the former is distinguished from the latter by the following characteristics: body fuscous and elongate in brachypterous morph (Fig. 1a, b). In contrast, A. nigrina has the following features: body dark grey and ovate in brachypterous morph.

Identification keys
Key to the species of Acalypta occurring in Japan -Basal part of antennal segment III not thickened A. marginata (Wolff, 1804) 4 Pronotum not less than 0.8 times as long as maximum width across paranota; discoidal area considerably expanded beyond apical fourth of hemelytron, distinctly wider than subcostal area 5 -Pronotum not more than 0.6 times as long as maximum width across paranota; discoidal area not expanded beyond apical fourth of hemelytron, not wider than subcostal area 6 5 Posterolateral angle of paranotum protruding posteriad; posterior process 2.5 times as wide as its length; costal area with a single row of areolae throughout its length; subcostal area with 5 rows of areolae at widest part; discoidal area with 5 rows of areolae at widest part rows of areolae in basal part, 2 rows in middle part and 3 rows in apical part; discoidal area narrower than subcostal area at widest part of each A. tsurugisana Tomokuni, 1972