Trigoniophthalmus ukrainensis Kaplin, 2020

Kaplin, Vladimir & Vargovitsh, Robert S., 2020, New species of bristletails of the family Machilidae (Microcoryphia) from caves in Abkhazia and Ukraine, Zootaxa 4885 (4), pp. 530-540 : 537-538

Trigoniophthalmus ukrainensis Kaplin , sp. nov.

Figs. 15–21

Diagnosis. Trigoniophthalmus ukrainensis sp. nov., with 2 + 2 eversible vesicles on urocoxites II–V, belongs to the subgenus Trigoniophthalmus s. str., which has been composed of only one species, T. alternatus (Silvestri, 1904) . The two species differ in the number of annuli in distal chains of flagellum, and the absence of numerous long, thin chaetae on the undersurface of the male maxillary palp and the dorsal surface of the labial palp.

Description. Holotype, male: body length 7.7 mm; body width 1.8 mm; antenna length 4.0 mm (broken); cercal length 3.0 mm. Coxal styli length 0.65–0.68 mm.

General body color (in ethanol) yellowish light brown, with brown-violet hypodermal pigment of light to medium intensity on antennal base, frons, gena, lateral sides of clypeus, mandibles, maxillae, hypopharynx, first palpomere of maxillary and labial palpi, labium, labrum and thoracic sterna. Scale color on surface of body light brown or brown. Antennae shorter than body (slightly broken). Distal chains of flagellum divided into 9–12 annuli (two apical chains broken). Clypeus and labrum with long thin chaetae. Cercal length about 0.4 times as long as body length, with two apical spikes, divided into 17 or 18 annuli. Each article of cercus with 2 or 4 rows of scales. Annuli of cerci, except for apical two, with 1 or 2 inner lateral hyaline spines.

Compound eyes slightly expanded, black (in ethanol). Length to width ratio of compound eye 0.9; ratio of line of contact to length of eye 0.50. Paired ocelli submedian, subtriangular, dark brown, 1.5 times wider than long. Ratio of distance between inner and outer margins of ocelli to total width of compound eyes 0.10 and 0.51, respectively ( Fig. 15 ).

Apical palpomere of maxillary palp 0.86 times as long as preceding one; ratio of length of fifth to fourth palpomere 1.3. Dorsal surface of 7th, 6th and 5th palpomeres of maxillary palp with 11, 9 and 3 hyaline spines, respectively ( Fig. 16 ). Undersurface of maxillary palpomeres and dorsal surface of labial palpomeres without numerous long thin chaetae. Apical labial palpomeres triangular-oval, 2.0 times longer than wide ( Fig. 17 ). Mandibles with three distal teeth ( Fig. 18 ).

Fore and middle femora and tibiae widened ( Fig. 19 ). Hind legs longer than forelegs, much longer than middle legs. Hind tarsus 1.15 and 1.25 times longer, respectively, than those of fore and middle legs. Hind tibia 1.17 and 1.34 times longer, respectively, than those of fore and middle legs. Fore femur with narrow sensorial field on the external distal part consisting of 4–5 groups of very small “rosette-shaped” sensilla ( Figs. 19, 20 ), each group containing about 12–16 sensilla. Ratios of length to width of femur, tibia and tarsus of middle leg shorter and relatively wider than those of fore and hind leg ( Table 5 ). Ratio of length of apical hind tarsomere to total length of hind tarsus 0.37. Trochanter, femur and tibia lacking long, thin chaetae. Ventral surface of femora, tibiae and tarsi without pigmented, spine-like macrochaetae. Pretarsi with arolium.

Middle and hind legs with coxal styli. Ratio of length of styli to width of middle and hind coxae 1.45 and 1.77, respectively.

Urocoxites I, VI and VII with 1+1, II–V with 2 + 2 eversible vesicles. Posterior angle of urosternites II–VI 78–81°, VII 86°, VIII 110°. Length ratios of urosternites, urocoxites and urostyli around 0.5 ( Table 6 ).

Thoracic tergites, urotergites I–IV, urosternites, urocoxites I–VIII without spines. Distribution of sublateral spines on urotergites V–X and urocoxites IX with sublateral spines ( Table 6 ). Urocoxites IX with 3 + 3 inner sublateral spines, missing on their outer sides ( Fig. 21 ).

Male genitalia with one pair of parameres on urite IX. Parameres with 1 + 5 divisions ( Fig. 21 ), surpassing apex of penis. Penis and parameres completely covered by coxites IX.

Material examined. Holotype: male (on slide) ( ZIN); Ukraine, Zakarpatska Oblast , Tyachiv District , near Pidplesha , E Carpathians, Krasna Mountain Range , 48°9’25”N, 23°49’1″E, elev. 698 m, Tsherlenyi Kamin Cave System , Kanyon Cave, ~ 5 m from the entrance, 23.01.2000 ( R. S. Vargovitsh).

Habitats. Trigoniophthalmus ukrainensis sp. nov. was collected on the wall ~ 5 m from the entrance. The present new species exhibits no morphological adaptations to life in caves.

Etymology. The new species is named after Ukraine, where it was collected.

Figures

FIGURES 15–21. Trigoniophthalmus ukrainensis sp. nov., holotype male. 15) Eyes and paired ocelli, front view. 16) Maxillary palp. 17) Labial palp. 18) Distal part of mandible. 19) Fore leg (part). 20) Rosette-shaped sensillum. 21) Urocoxite IX (without stylus) and paramere. Scale bars: 0.1 mm.