Pteremis tenebricus, Roháček, 2024

Roháček, Jindřich, 2024, The genus Pteremis (Diptera: Sphaeroceridae) in the West Palaearctic area, with description of four new species, Acta Entomologica Musei Nationalis Pragae 64 (1), pp. 153-206 : 173-176

Pteremis tenebricus sp. nov.

( Figs 62–74 )

Type material. HoLoTYPF: J ( DEBU), labeled: ‘ SPAIN:Sierra Nevada, Hwy, 2270m; 11.viii.86, J.R.Vockeroth; under grass of dry stream’ and ‘ Holotypus J Pteremis tenebricus sp. n., J. Roháček des. 2023’ (red label) ( Fig. 63 ). The specimen (see Fig. 62 ) is dry mounted on triangular pinned card, with abdomen (dissected) and left wing removed and all detached parts preserved in glycerine in coalesced plastic tube pinned below specimen.

Description. Male ( Figs 62, 64 ). Total body length 2.22 mm; general colour blackish brown (darkest of all fully winged Pteremis species) with dark greyish brown microtomentum but subshining dorsally on thorax and abdomen. Head ( Figs 62, 64 ) about 1.55× higher than long, largely dark brown to (posteriorly) almost black. Frons with microtomentose pattern similar to that of P. fenestralis but darker, all dark brown to blackish, only anteriorly narrowly brown to reddish brown. Orbits, interfrontalia and frontal (including ocellar) triangle with (rather dark) silvery grey and slightly glittering microtomentum; stripes surrounding (very) narrow interfrontalia almost black, with dull dark grey (with some bluish tinge) microtomentum, forming incomplete (medially interrupted) M-shaped mark; frontal triangle recognized by somewhat glittering microtomentum and reaching to anterior fifth of frons; anterior margin of frons only medially and laterally narrowly brown to reddish brown. Frontal lunule pale brown and pale grey microtomentose (lightest of head structures) and contrasting with darker brown face, the latter sparsely grey microtomentose and subshining; medial carina poorly developed. Gena concolorous with face, brown to dark brown and dark dull microtomentose; postgena with shining black perpendicular stripe. Cephalic chaetotaxy ( Fig. 64 ) closely resembling that of P. fenestralis but pvt weak, with apices meeting medially; occe and occi subequal but occi only very slightly inclinate; vti longest of frontal bristles, somewhat longer than vte; oc only as long as occe; posterior ors slightly longer than oc and about 1.5 times as long as anterior ors; 3 strong (all medially meeting or crossed) + 1 small (foremost) ifr (the latter on right side only); 3 or 4 distinct ads; g relatively robust and also 2 setae behind longer than peristomals; both vi lost in holotype but obviously very long and robust; 6 short peristomal setulae and also both postgenal setae weak, slightly longer than peristomals. Eye subcircular (23:21), with longest diameter 3.9 times as long as smallest (anterior) genal height.Antenna dark brown, with pedicel darkest; 1 st flagellomere with whitish ciliation on apex only slightly longer than cilia on arista. Arista about 3.7 times as long as antenna, with very short dense ciliation.

Thorax as in P. fenestralis but generally darker brown, also notopleural area, sutures between pleural sclerites and ventral part of sternopleuron brown ( Figs 62, 64 ). Thoracic chaetotaxy almost identical to that of P. fenestralis , only outer pa distinctly longer than dc and/or laterobasal sc (length of apical sc unknown because both setae are broken off) and only 1 long (posterior) stpl visible because anterior stpl is reduced to a hardly discernible microseta.

Legs distinctly darker and less variegated than those of P. fenestralis , having also trochanters, tibiae and tarsi brown or dark brown, only knee of fore leg, mid trochanter and tarsus pale brown or ochreous. Pedal chaetotaxies differing from those of P. fenestralis as follows: f 2 anteriorly with a short subapical row of 3 robust but short setae. t 2 dorsally ( Figs 69, 70 ) with all macrosetae more robust, and longest distal dorsal (or slightly posterodorsal) seta inserted more distally than long distal anterodorsal ( Fig. 69 ); va seta distinctly shortened, only about half length of vpa and much weaker (see Figs 66 , 70 ), and posterior subapical seta more robust although short ( Fig. 71 ). Ratio t

2

: mt

2

= 1.92.

Wing probably largest (compared to body) of all Pteremis species ( Fig. 62 ), relatively long, distally less rounded and its membrane less brownish clouded ( Fig. 65 ). C produced far beyond apex of R 4+5. R 4+5 distinctly sinuate but its distal half somewhat straightened (less curved) than in P. fenestralis and anterior outer corner of dm cell more obtuse-angled. A 1 well visible (distinctly pigmented) in its distal sinuate part ( Fig. 65 ). Anal lobe and alula also somewhat larger than those of P. fenestralis . Wing measurements: length 2.18 mm, width 0.95 mm, C-index = 1.28, r-m\dm-cu: dm-cu = 2.29. Haltere brown, darker on knob paler on stem and all light grey microtomentose.

Abdomen blackish brown, largely constructed as in P. fenestralis and with similar setosity. Owing to damage, only posterior half of preabdomen and postabdomen can be described. T4 more transverse than that of P. fenestralis but T5 similar in both species. Also S3 and S4 as those of P. fenestralis , thus S4 longest and widest abdominal sternum. However, S3 and S4 with more and stronger short setae than those on disc of adjacent terga but setae in posterior corners of S3 and S4 short and weak. S5 ( Figs 74 ) distinctly shorter and narrower than S4, thus less transverse than that of P. fenestralis and, in contrast to the latter, relatively densely, shortly and uniformly setose, with only setae at posterior margin somewhat longer and with small (shortened) pale-pigmented and finely micropubescent shortly crescent-shaped area in front of simple but dense posteromedial comb of fine spines. S6+7 strongly asymmetrical, with usual transverse dark-pigmented ledge but original S7 with dark posteroventral projection (longer and darker than that of P. fenestralis ) bent inside postabdomen; S6+7 with 3 + 2 distinct setae but S8 with only a pair of setulae, yet smaller than those of P. fenestralis .

Genitalia. Epandrium ( Figs 67, 68 ) similarly formed as in P. fenestralis but more rectangular in caudal view ( Fig. 67 ), with slightly wider anal fissure. Cerci markedly different from those of both P. fenestralis and P. pulliceps , prolonged and flattened ventrally, in lateral view ( Fig. 68 ) most resembling those of P. canaria but the flattened apex of cercus pale-pigmented and bare, without micropubescence ( Fig. 67 ). Medandrium largely as in P. fenestralis . Hypandrium ( Fig. 68 ) with medial apodeme longer and more robust than in P. fenestralis but strongly asymmetrical as in all relatives. Gonostylus ( Figs 67, 68, 72 ) larger, compared to epandrium, than in all other Pteremis species. Similar to P. fenestralis and some other species in having anterior lobe ( Fig. 72 ) with short pointed anterodorsal process but differing from all of them by very robust, distally darkened ventral, posteromedially curved (see Fig. 67 ) projection having simply pointed apex, and by 3 short external setae dorsally, behind anterodorsal pointed process. Posterior lobe of gonostylus (dotted in Fig. 72 ) relatively small and with terminal spine slender. Aedeagal complex ( Fig. 73 ) characterized by (dorsoventrally) short phallophore having short but acutely pointed projection on apex. Distiphallus relatively slender (its base in particular) but distally dilated, more than in P. fenestralis and with lateral membrane between slender band-like lateral and dorsal sclerites with some pale tubercles among micropubescence ( Fig. 73 ). Postgonite most similar to that of P. pulliceps but distally yet more slender (less dilated) and proximally with distinct posterior emargination ( Fig. 73 ). Ejacapodeme larger and with longer and slender distal digitiform, somewhat sinuate process (see Fig. 73 ).

Female unknown.

Etymology. Named for its unusually dark body colouration. The name is a Latin adjective tenebricus (= dark, gloomy).

Comments. Pteremis tenebricus sp. nov. is surely the darkest species of the P. fenestralis alliance. It differs from relatives also by more elongate wings with less rounded apex and has va seta on mid tibia only about half length of vpa seta, thus shorter than that of P. pulliceps sp. nov. but longer than that of P. ferreus sp. nov. It is best characterized by a shortened pigmented area in front of posteromedial comb of spines ( Fig. 74 ) of male S5 and by a relatively large (compared to epandrium) gonostylus having particularly enlarged and medially curved ventral, posteromedially directed projection of its anterior lobe ( Fig. 72 ). However, it differs from other species also by detailed formation and structures of male cercus and aedeagal complex (phallophore, distiphallus, postgonite). Unfortunately, the female of P. tenebricus remains unknown. It would be particularly important to know the shape and armature of its S8 and spermathecae to recognize if it is more closely related to P. fenestralis or to P. pulliceps .

Biology. The only known specimen was collected on 11th August ‘under grass of dry stream’ in high montane habitat (2,270 m a.s.l.) of the Sierra Nevada Mts. Interestingly, this male holotype was captured by J. R. Vockeroth together with 2 JJ 2 ♀♀ of true Pteremis fenestralis .

Distribution. Spain (Sierra Nevada Mts).

Figures

Figs 62–66. Pteremis tenebricus sp. nov., male holotype. 62 – whole specimen after dissection (most of abdomen and left wing removed), left laterally; 63 – labels of the holotype; 64 – head and thorax, left laterofrontally; 65 – left wing; 66 – left mid tibia, anteriorly. Scales = 0.5 mm. Photo by J. Roháček.

Figs 67–74. Pteremis tenebricus sp. nov., male, holotype. 67 – external genitalia, caudally (aedeagal complex, left gonostylus and micropubescence of right cercus omitted); 68 – ditto, left laterally; 69 – left t2, dorsally; 70 – left t2 and mt2, anteriorly; 71 – apex of left t2 and mt2, posteriorly; 72 – gonostylus, laterally; 73 – aedeagal complex, laterally; 74 – male S5, ventrally. Scales = 0.1 mm (Figs 67, 68, 73, 74), 0.2 mm (Figs 69–71), 0.05 mm (Fig. 72).