Revision of the flat bug family Aradidae from Baltic Amber IX . Aradus macrosomus sp . n . ( Hemiptera : Heteroptera )

The present paper is a continuation of previous contributions describing fossil Aradus species from Baltic Amber inclusions (Heiss 1998, 2002, 2013). Aradus macrosomus sp. n. is a wellpreserved large new species which is described and illustrated herein. It differs by a combination of characters from the known Eocene and extant Aradus taxa, documenting again the unexpected richness of species diversity preserved in Baltic Amber.


Introduction
Baltic Amber, a fossilized tree resin found on or near the shores of the eastern Baltic Sea, represents the largest deposit of amber in the world.It is exceptionally rich in well-preserved inclusions of botanical and zoological objects, particularly arthropods.The origin, genesis, properties, age and the flora and fauna of Baltic Amber are largely discussed by Grimaldi (1996) and Weitschat and Wichard (1998).
Among the insect fauna, Heteroptera have attracted considerable attention and taxa from at least 3 aquatic and about 14 terrestrial bug families have been described since the first description by Germar and Berendt (1856;Weitschat andWichard 2002, Grimaldi andEngel 2005).
Another species, A. grabenhorsti Heiss, 2013 was described based on a specimen from Bitterfelder Amber (Saxonia, Germany), which presumably is of the same Eocene age as Baltic Amber.Specimens from Baltic Amber agree in all essential characters which could be assigned to this taxon and were thus included as paratypes in the type series.

Material and methods
The Amber inclusion used in this study is preserved in the collection of the author at the Tiroler Landesmuseum, Innsbruck, Austria.
Photos were taken through an Olympus SZX 10 binocular microscope with Olympus E 3 digital camera and processed with Helicon Focus 4.3 software, using Adobe Photoshop and Lightroom 2.3.
Measurements were taken with a micrometer eyepiece, 20 units = 1 mm, and are given in millimetres, unless otherwise stated.Material examined.Holotype female in a honey-coloured transparent piece of Baltic Amber, which will be embedded in a block of epoxid resin (He-BB-Ar-40).

Taxonomy
The specimen is dorsally and ventrally clearly visible, without a frequently occurring white incrustation (German: Verlumung).Antennae and legs are complete, the latter are bent ventrally.
Diagnosis.Species of larger size (9.2 mm) with long antennae, which are beset with tubercles bearing stiff bristles.Lateral margins of pronotum angulate and serrate, constricted anterolaterally.Abdomen widely rounded, connecting vein M-Cu of corium situated posterior to A-Cu.
Description.Macropterous female.Body with fine granulation.Colour light brown with darker patches on head, pronotum and hemelytra.
Head.Wider across eyes than long (32 / 29).Clypeus subparallel, twice as long as antennal segment I, apex rounded.Antenniferous tubercles subparallel, acute, shorter than antennal segment I. Lateral margins begranulate, a distinct preocular tubercle present.Antennae slender, 1.72 × as long as width of head; antennal segment I short but widest, here secondarily depressed; II longest, thinner at middle than at its ends; III shorter than II tapering toward base; IV shortest with pilose apex.Relative length of antennal segments I / II / III / IV = 6 / 23 / 17 / 11.Eyes reniform, large, protruding laterally.Postocular lobes rounded, their margins beset with some larger tubercles.Vertex with U-shaped depression.Rostrum arising from an open atrium, four-segmented, reaching anterior 1/3 of prosternum.
Pronotum.2.56 × as wide as long (64 / 25).Lateral margins irregularly serrate, angularly expanded at middle then strongly converging and constricted anteriorly.Anterolateral angles rectangular, anterior margin straight.Surface only slightly convex, with 4 longitudinal carinae, the median ones of full length, the lateral ones shorter, reaching to shallow transverse impressions.Humeral angles slightly carinate.Posterior margin concave at middle, rounded laterally.
Hemelytra.Basal lateral expansion of corium rounded; posterior angle of corium reaching posterior margin of dorsal external laterotergite (deltg) V. Veins distinct, M-Cu situated posterior to A-Cu.Membrane with 4 distinct veins, reaching to anterior margin of tergit VII, surface wrinkled.
Abdomen.Widely rounded; lateral margins of deltg II-VI slightly convex posteroexterior angles not produced; deltg VII broadly rounded posteriorly, paratergites VIII cleft at middle, apex rounded with a blunt lateral tooth.Ventral side with a longitudinal groove, reaching from sternite VIII to prosternum.Spiracles II-VII ventral and far from lateral margin, VIII lateral and visible from above.
Measurements.Length 9.2 mm; length of antennae 2.25 mm; width of abdomen 5.05 mm; width of corium 3.75 mm; width of tergite VIII 1.7 mm.Etymology.The epithet refers to its unusual large size, from "macros" <Greek> large and "soma" <Greek> body.

Discussion
The new species can be distinguished at once from all other species of Aradus described so far of Baltic amber by a combination of characters not occurring otherwise, e.g., its large size, wide rounded body, structure of head with reniform laterally protruding eyes, long and thin antennae, and shape of the pronotum and scutellum.It shows only a superficial similarity to A. lativentris Heiss (2002b) andA. velteni Heiss (2002c), which, however, are of smaller size and the structure and shape of head, antennae and pronotum are different.There does not seem to be a close relationship with the extant species of Aradus.