Merothrips aithiopicus, Ulitzka, 2020

Ulitzka, Manfred R., 2020, Two fossil thrips from Ethiopian amber (Thysanoptera) with description of Merothrips aithiopicus sp. n. (Thysanoptera: Merothripidae), Zootaxa 4786 (2), pp. 283-288 : 284-285

Merothrips aithiopicus sp. n. ( Figs 1–4 )

Female macroptera. Body protracted (probably by deformation of the resin), antennae therefore torn into single segments and many setae slightly pulled away from their former points of attachment (fig. 2); head crushed dorsally at base, pronotum dented (fig. 2); all legs angled; right wings overlapping on top of the body, left fore wing torn off and lying approximately 4.5mm away, left hind wing slightly spread (fig. 1). Main colour greyish brown (fig. 1); antennae, head, pronotum and forelegs darker; all major setae dark as well as wing veins and fringes; fore wings tinged grey-brown, hindwings shaded slightly pale grey.

Head (fig. 2) wider than long, cheeks slightly rounded towards base; most head setae not ascertainable, except a pair of conspicuous ocellar setae (s3) and a pair of long postocular setae attached closely to the hind margin of the eyes. Eyes large, with about 15–20 facets, their front margin protruding over base of antennae. Mouth cone short. Antennae moniliform (figs 1, 2), 8-segmented, with all segments bearing long setae; segments I not clearly visible; segments II–IV inverse conically shaped, III and IV tapering distally; V–VII barrel-shaped, VIII spindle-shaped; shape of apical sensoria on III and IV transvers, however, not clearly assessable (only visible on the right antenna). Pronotum without visible sculpturing; trapezoidal, with longitudinal sutures near the lateral margins; length/width ration not assessable (deformed); with one pair of strong anteroangular setae, three pairs of anteromarginal setae and one pair of posteroangular setae (the slightly weaker setae lying close to both posteroangular setae most likely derive from the coxae, c.f. fig. 2: sco), posteromarginal setae not visible. Mesonotum transversally striate in front of median setae but smooth towards hind margin (fig. 2); lateral setae strong. Fore wings narrow, with two longitudinal veins and a cross vein one third of the wing length away from the base (fig. 3); first vein with a row of 17, second vein with 15 setae; clavus with one marginal seta; wing fringes long and straight. Fore femora stout; middle and hind femora not enlarged (fig. 1). All tibiae dorsally bearing a long median seta; distal tooth on fore tibiae not assessable (possibly broken off). Tarsi two-segmented; basal tarsomere of fore tarsi with a long apical seta. Abdominal tergites with faint lines of transverse sculpture; tergites IX and X with long setae; tergite X with a pair of trichobothria with long axial setae (fig. 4). Sternites without accessory setae. Ovipositor weak.

Measurements. Female NHMW, N6974; in microns: Body length 872. Head, length 72; width about 48. Eyes, length 29; width 14. Hind ocelli, diameter 16. Ocellar setae s3 48; postocular setae 19. Prothorax, length about 84; width not measurable (deformed); anterior marginal setae 7–9, anteroangular setae 17, posteroangular setae 42, discal setae 10–12. Pterothorax, largest width 101. Mesonotal setae s1 10, distance between s1 29. Abdomen, length 476; largest width 132 (at segment VI). Antennae stretched over 286 (sum of the length of all segments 159); length (largest width) of segment I about 7 (12), II 21 (16), III 24 (16), IV 24 (12), V 19 (10), VI 19 (8), VII 19 (7), VIII 26 (7). Fore wings, length 420; width in the middle 14; wing fringes 120–180.

Specimen studied. Holotype female; fossil from Ethiopian amber collected nearAlem-Ketema, Ethiopia (10°08’45’’N, 38°57’56’’E), see also Schmidt et al. (2010). Stored in the collection of the Naturhistorisches Museum Wien, Vienna, Austria; NHMW, N6974 .

Syninclusions: many particles of plant detritus, lawns of spherical and rod-shaped bacteria, fungal mycelia and some spores as well as a nematode and a small part of another arthropod.

Etymology. The species epithet aithiopicus derives from the classical Greek word ΑΙΘΙΟΠία (Aithiopia), the ancient geographical name for a historic region in Africa, which included Ethiopia, the country where the amber deposit is located.

Diagnosis. Even though the pair of lobes on the posterior margin of the seventh abdominal sternite is not visible the form of the antennal sensoria (fig. 2), the presence of trichobothria on abdominal tergite X (fig. 4), the shape of the wings with pointed tips (fig. 3) as well as the enlarged fore femora (figs 1, 2) indicate that the new species is attributable to Merothripidae . Species associated with this family usually have nine-segmented antennae, apart from members of Merothrips Hood , which have eight antennomeres. The classification of the new species into this genus is also supported by the trapezoidal pronotum, the wing venation and the chaetotaxy of the wing scale (c.f. Bhatti 2006; Mound & O’Neill 1974).

As mentioned above, three further fossil Merothrips -species are known, all described from Baltic Eocene amber: M. balticus , M. dietrichi and M. fritschi . From M. balticus the new species (as well as M. dietrichi and M. fritschi ) can be easily distinguished by the presence of only one pair of posteroangular pronotal setae (fig. 2). In M. dietrichi these setae are short (23) but longer in M. aithiopicus sp. n. (42) and fritschi (43–52). The holotype of M. fritschi , unfortunately, was lost during the Second World War ( Ulitzka 2015), but the description by Priesner (1924) provides sufficient detail to distinguish it from M. aithiopicus sp. n.: the new species is slightly smaller, but it has proportionally much shorter fore wings and less protruding hind femora. Furthermore, M. fritschi has antennal segments I and II dark whereas the distal segments are clear, the new species, however, has completely dark antennae (fig. 1).

Compared to extant species M. aithiopicus sp. n. resembles M. productus Hood , but has a less elongated head.

Figures

FIGURES 1–7. Ethiopian amber fossils. Merothrips aithiopicus sp. n. holotype female 1–4: (1) dorsal view; (2) head, prothorax and metathorax (sa- sensory areas; soc- ocellar setae s3; spo- postocular setae; spa- pronotal posteroangular setae; sco- coxal setae); (3) left fore wing (cross vein indicated); (4) abdominal segments VII–X (spiracles indicated white, trichobothria indicated black).Thripidae, cf. Scirtothrips, female second instar larva 5–7: (5) dorsal view; (6) imprint of caudal abdominal segments (d1–d3- dorsal setae; sl- lateral seta; v1–v2- ventral setae); (7) right antenna.