Rohrthrips setiger, Ulitzka, 2022

Ulitzka, Manfred R., 2022, New genera and species of Rohrthripidae (Thysanoptera: Tubulifera) from Burmese Cretaceous amber, Zootaxa 5162 (1), pp. 1-36 : 18-19

Rohrthrips setiger sp. n.

( Fig. 18 )

Female. Body extended, distal abdominal segments, however, directed to the right; pronotum dented on the left side; right fore wing slightly spread, right hind wing turned under body, left wings overlapping body; right hind leg folded under abdomen, other legs bent but well visible; anterior and mediolateral setae of pronotum as well as major head setae not visible (whether broken off or vestigial).

Colour uniformly dark brown, including antennae and legs; all major setae dark as well as wing veins and fringes; wings shaded brownish.

Head longer than wide; slightly prolonged in front of and incised behind compound eyes; sculpture not clearly assessable, some parts give the impression of a coarse reticulation. Cheeks straight, barely tapering towards head base; with a few short lateral setae (their number not assessable). One pair of ocellar setae visible close to base of antennae; pointed, about as long as antennal segment I. Postocular setae not visible. Eyes slightly protruding at front margin; laterally occupying somewhat more than one third of the head length; not prolonged ventrally. Hind ocelli large and close to compound eyes, fore ocellus much smaller and directed forwards. Antennae nine-segmented; segment I barrel-shaped; segment II asymmetrically bent outwards, basally with a stout pedicle; III–VII with a much more slender pedicle at base, then inverse cone shaped and tapering distally from level of sense cones; VIII spindleshaped; IX style-shaped. Sensorium on segment II not visible; sense cones of the following segments deformed, their number difficult to assess, at least one outer and one inner on III–V, one inner on VI and one inner on VII. Mouth cone pointed, long but not reaching base of prosternum. Maxillary palps not assessable. Pronotum wider than long, trapezoidal; anteroangular and mediolateral setae very short (or broken off), posteroangular setae long and pointed, anteromarginal and posteromarginal setae minute; epimeral setae long and hair-like, longer than other pronotal major setae. Mesonotum sculptured finely reticulate; mesonotal setae not visible. Fore wings becoming progressively larger in distal half; with two veins ( Fig. 18 ). First wing vein reaching costa near wing apex; furnished with 13 dispersed setae (six of these setae in distal wing half are about as long as distance between the wing vein and fore margin of wing, or even longer); second vein developed in basal third only, without any setae. Fringe cilia straight, for the most part slightly enlarged at base but embedded into the wing membrane, only some fringes – particularly on hind wings – clearly on sockets. Duplicated cilia present around apical margin of wing; running parallel to normal wing fringes. Hind wing without any veins. Wing membrane of fore and hind wings without microtrichia. Wing coupling system hamulo-frenate (number of hamuli not assessable). Fore legs with femora enlarged, but not as stout as in other species; fore tarsi with a strong tooth and a strong hamus. Mid and hind legs slender. All tibiae with one long dorsal seta; mid and hind tibiae terminally each with three spines; mid and hind tarsi two-segmented, with hamus. Abdominal tergites without wing-retaining setae; lateral setae pointed, recurved, long but delicate; setae s3 on IV–VII conspicuously longer than other lateral setae. Basal abdominal segments not assessable (hidden by wings); IX conical, with setae s2 long but shorter than tube. Abdominal segment X (tube) long and evenly widened towards base; with terminal crown of short anal setae (shorter than half the length of the tube).

Measurements. Female (in microns): Body, length 1960. Head, length 255; largest width 206. Eyes, length 87; width 49. Hind ocelli, diameter 19; distance between the hind ocelli 76; fore ocellus, diameter 13. Ocellar setae 38. Pronotum, length 246; width not measurable (dented on right side); posteroangular setae about 20 (difficult to measure) and epimeral setae 164. Pterothorax, largest width 328. Abdomen, length 1040; largest width 510 (segment III); segment X (tube) length 270; basal width 76. Setae on tergite IX, s1 107; s2 252; s3 202. Antennae, length 533; length (largest width) of segment I 71 (28), II 68 (28), III 81 (34), IV 68 (31), V 68 (28), VI 56 (19), VII 53 (19), VIII 46 (16), IX 22 (9). Sense cones not measurable. Fore wings, length 1088; largest width 255.

Material studied. Holotype female MU-Fos-147/1 ( Fig. 18 ); inclusion in Burmese amber from Hukawng Valley, Kachin State, Myanmar; purchased by the author on eBay from Terry Su, eBay username “burmite-miner”; deposited in the author’s collection.

Syninclusions. Numerous hairs of another arthropod; small particles of plant detritus, small dark droplet and many crystals of pyrite around the thrips inclusion.

Etymology. The species epithet setiger comes from the Latin words seta, meaning “bristel”, and gerere, meaning in the character of the suffix -ger “furnished with”. It refers to the wing vein of this species that is furnished with numerous longer setae ( Fig. 18 ).

Differential diagnosis. Rohrthrips now comprises 12 species that can be distinguished primarily by their wing veins and the length-to-width ratio of their tubes. In contrast to all other species R. libanicus , rhamphorhynchus sp. n. and setiger sp. n. have an additional but shorter second vein on the fore wings (see Figs 17–18 and Ulitzka 2018, p. 556 Fig. 13 ). R. libanicus from Lebanese amber can be distinguished from the latter two species from Burmese amber by its shorter tube. Within the species from Burmite, R. rhamphorhynchus sp. n. has a long and slender mouth cone protruding over the base of the prosternum ( Fig. 37 ), whereas the mouth cone in R. setiger sp. n. is much shorter. These species, moreover, can be distinguished by the number of setae on their first wing vein: In R. setiger sp. n. the vein has much more stout setae (13); in R. rhamphorhynchus sp. n. it is less setose (four short and one longer setae). The species with only one wing vein may be classified into two groups with regard to the shape and length-to-width ratio of their tubes. The first group contains species with a short and bulky tube (length-to-width ratio 2.3–2.5): R. breviceps , R. maryae and R. patrickmuelleri ; in contrast, the second group contains species with a long and slender tube (length-to-width ratio 3.2–5.9): R. brachyvenis sp. n., R. burmiticus , R. jiewenae , R. multihamuli sp. n. and R. schizovenatus (see also Ulitzka 2019). In the first group, R. breviceps ( Fig. 13 ) may be distinguished by its conspicuously short head, the shortened wing vein (0.8 of wing length) and the smaller body size (1.3mm). Some character states of this species, however, are similar to those of R. maryae and R. patrickmuelleri , such as the length of the epimeral setae in R. patrickmuelleri , and in R. maryae the head, which is also somewhat wider than long. However, both of the latter species are larger yet their antennae are much shorter. R. maryae and R. patrickmuelleri may be distinguished by their wings. In both species the wing vein meets the costa close to the wing apex. In R. patrickmuelleri , however, the vein is colourless subbasally and coloured pale greyish-brown distally and it is conspicuously straight except for the short bending close to its tip. In contrast, the vein is dark brown in the distal two thirds and curved forwards from the middle of its length in R. maryae . Furthermore, the wings of the latter species are broader apically and it is much larger than R. patrickmuelleri , with the abdomen conspicuously broad.

In the second group R. multihamuli sp. n. differs significantly from all other species; on the one hand by its large size (2.8 mm) and on the other hand by the shape of antennal segments III and IV, which are not inversely conical but cylindrically elongated ( Figs 15 , 38 ). R. burmiticus and R. jiewenae differ from R. brachyvenis sp. n. and R. schizovenatus with regard to their long wing vein reaching the costa at base of the wing tip rounding. These species are quite similar regarding their body shape and structures; however, they are clearly distinguished by the conspicuously short sense cones in R. jiewenae . In R. brachyvenis sp. n. and R. schizovenatus the wing vein is shortened. In R. schizovenatus it hardly reaches the last quarter of the fore wing and it is apically split into two branches, each ending with a terminal seta. Furthermore, R. schizovenatus has a very long and slender tube (length-to-width ratio about 5.1) and antennal segment III is strikingly long (>100µm). In R. brachyvenis sp. n. antennal segment III and the tube (length-to-width ratio about 3.2) are shorter. Furthermore, the wing vein in this species is not split and slightly longer, reaching the last fifth of the wing ( Fig. 12 ). R. brachyvenis sp. n., moreover, is the only species of Rohrthrips that clearly shows four sense cones on antennal segment III. However, this feature should be considered with great care. In other species, further sense cones may also be present but may lie completely above or below the segment and thus remain hidden. R. pandemicus sp. n., finally, is the only micropterous species within that genus ( Fig. 16 ). It has no ocelli, and its compound eyes are reduced to a few ommatidia only. Most likely, however, it is not a distinct species but the micropterous form of R. maryae or possibly R. breviceps .

Figures

FIGURES 16–18. Rohrthrips spp. (16) Rohrthrips pandemicus sp. n. holotype female aptera, dorsal view; (17) Rohrthrips rhamphorhynchus sp. n. holotype, dorsal view, indicated: second vein at base of fore wing; mouth cone outlined white; (18) Rohrthrips setiger sp. n. holotype female, right fore wing, indicated: second wing vein at base.

FIGURES 12–15. Rohrthrips spp. (12) Rohrthrips brachyvenis sp. n. holotype female, dorsal view; (13) Rohrthrips breviceps male, dorsal view (Note: the median shading makes the tube appear narrow, but the lighter edges are part of the tube, which actually is broad at base); (14) Rohrthrips jiewenae male, dorsal view; (15) Rohrthrips multihamuli sp. n. holotype female, head and pronotum, antennal segments III–IV indicated with roman numerals.

FIGURES 35–38. Line drawings of Rohrthripidae. Head, mouthparts and prothorax (md: mandibula, mx: maxillary stylets) 35–37: (35) Adstrictubothrips mirapterus gen. et sp. n. holotype female; (36) Gemineurothrips peculiaris gen. et sp. n. holotype (spa: posteroangular setae, left broken off and lying close to coxa; scx: coxal setae); (37) Rohrthrips rhamphorhynchus sp. n. holotype. (38) Rohrthrips multihamuli sp. n. holotype; left antenna, segment numbers in Roman numerals, indicated: ventral projections on segments V–VII (cs: campaniform sensillum, uncolored trichomes indicate presumptive sense cones).