Pteremis apterina, 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 : 187-194

Pteremis apterina sp. nov.

( Figs 119–145 )

Type material. HoLoTYPF: J ( SMOC), labelled: ‘ AZORES: São Miguel I., Sete Citades 1.5 km SE, 35°51ʹN 25°47ʹW, J. Roháček leg.’, ‘sifting detritus in broadleaved forest, 31.8.2006 ’, ‘Mus. Silesiae Opava, Inv.č. d 097 9-2006’, ‘ HOLOTYPUS J, Pteremis apterina sp. n., J. Roháček des.2023’ (red label) ( Fig. 120 ).The specimen (see Fig.119 ) is intact,dry mounted on triangular pinned card. PARATYPFs: PORTUGAL: AZORES: SẪO MIGUEL I.: 8 JJ 4 ♀♀ (1 J headless, 2 JJ 1 ♀ genit. prep.), with same data as for holotype; 2 JJ 3 ♀♀ (1 ♀ genit. prep.), with same data but collected 8.ix.2006; 3 JJ 2 ♀♀, with same data but collected 11.ix.2006; 2 JJ, São Miguel I., Caldeiras nr. Ribeira Grande, 37°48ʹN 25°29ʹW, sifting detritus in broadleaved forest, 5.ix.2006; 2 ♀♀, São Miguel I., Caldeira Velha (nr.Ribeira Grande), 37°47ʹN 25°30ʹW, sifting detritus in broadleaved forest, 7.ix.2006, all J. Roháček leg. ( SMOC). TERCEIRA I.: Caldeira de Serra de Santa Bárbara (TER-NFSB-T164), 38°44′06″N, 27°18′26″W, 940 m, laurel forest, pitfall trap T92-E4, 1 J 1 ♀, T92-E8, 1 J, T92-E12, 1 J 1 ♀, T92-E14, vii. 2008, 1 J 1 ♀, T92-E22, vii. 2008, 3 JJ 2 ♀♀, T92-E24, 1♀, T92-E26, 1♀, T92-E28, 2 ♀♀, T92-E30, 1J 2♀♀, T92-T11, 2♀♀, T92-T15, 1J (all dried from ethanol, 1 J 1 ♀ genit. prep.), all P. A. V. Borges et al. leg. (7 JJ 11 ♀♀ DTP, 2 JJ 2 ♀♀ SMOC). SANTA MARIA I.: Pico Alto, 36°58′25″N, 25°05′23.07″W, 437 m, pitfall traps in exotic plantation of Cryptomeria japonica , 26.v.–12.vi.2009, 3 JJ 3 ♀♀ (all dried from ethanol, 1 J genit. prep.), P.A.V. Borges et al. leg. (2 JJ 2 ♀♀ DTP, 1 J 1 ♀ SMOC); Santa Maria I., Anjos, 36°59′29″N, 25°08′23″W, 181 m, pitfall traps in exotic plantation of Acacia sp. , 12.–18.vi.1990, 79 JJ 42 ♀♀ (all dried from ethanol, 1 J 1 ♀ genit. prep.), P. A. V. Borges et al. leg. (64 JJ 32 ♀♀ DTP, 5 JJ 5 ♀♀ SMOC, 10 JJ 5 ♀♀ NMPC). All paratypes with ‘ PARATYPUS J or ♀, Pteremis apterina sp. n., J. Roháček des. 2023′ (yellow label).

Additional material examined (excluded from type series, poorly preserved or damaged specimens, all in ethanol). PORTUGAL: AZORES: TERCEIRA I.: Caldeira de Serra de Santa Bárbara (TER-NFSB-T164), 38°44′06″N, 27°18′26″W, 940 m, laurel forest, pitfall trap T92-E10, vii. 2008, 1 J 1 ♀, T92-E14, vii. 2008, 1 J 2 ♀♀, P. A. V. Borges et al. leg.

SANTA MARIA I.: Anjos, 36°59′29″N, 25°08′23″W, 181 m, pitfall traps in exotic plantation of Acacia sp. , 12.–18.vi.1990, 120JJ 29 ♀♀ (7JJ 1 ♀ immatures), P. A. V. Borges et al. leg.; Santa Maria I., Pico Alto, 36°58′25″N, 25°05′23.07″W, 437 m, pitfall traps in exotic plantation of Cryptomeria japonica , 26.v.–12.vi.2009, 1 J (headless), Paulo A. V. Borges et al. leg (all in DTP).

Description. Male ( Figs 119, 124 ). Fully apterous, also halteres entirely absent. Total body length 1.67–2.58 mm; general colour blackish brown (only teneral specimens pale brown) with greyish brown microtomentum, dorsal side of thorax and abdomen subshining (cf. Fig. 121 ), head, thoracic pleuron and abdominal sterna duller ( Fig. 119 ).

Head ( Figs 119, 123, 124 ) 1.3–1.4× higher than long, blackish brown to (posteriorly) black, with only frons anteriorly lighter. Frons generally darker but with microtomentose pattern (see Fig. 123 ) resembling that of P. fenestralis ; dark brown to blackish except for orange-brown or reddish brown anterior margin but extent of this anterior colouration variable, ranging from narrow marginal stripe to covering (medially, between interfrontalia and frontal triangle) anterior half of frons; occiput almost black but with dense greyish brown microtomentum (as is that on mesonotum). Orbits, interfrontalia and frontal (and ocellar) triangle with silvery grey (more or less glittering) microtomentum; also incomplete (medially interrupted) dull blackish M-shaped mark between them developed; frontal triangle delimited by silvery grey microtomentum and almost reaching anterior margin of frons but its apex often unclear due to sparse microtomentum. Frontal lunule orange-brown to brown, always with light grey microtomentum, thus looking somewhat lighter than face or anterior margin of frons. Face brown to dark brown (darkest in facial cavities below antennae), sparsely grey microtomentose and subshining; medial carina developed, mainly distinct dorsally. Gena brown to dark brown, greyish brown microtomentose; postgena with usual blackish and shining perpendicular stripe. Cephalic chaetotaxy ( Figs 119, 123 ): cephalic setae somewhat stronger than in other Pteremis species; true pvt absent but a pair of minute divergent medial postocellar setulae behind ocellar triangle present; and occi distinctly inclinate, slightly to distinctly longer than occe and about two-thirds of vti; vti and vte subequal or vti somewhat longer (longest of frontal bristles); oc usually shorter than posterior ors; 2 ors but only posterior robust and long; anterior ors short and weak, less than half length of posterior ors; 4 (rarely only 3 on one side) ifr, two middle pairs usually long and robust (one of them usually longer and crossed), others short and weak, 1 microseta in front of anterior ifr also developed; 2 or 3 very minute ads as in P. fenestralis ; g and 1 or 2 shorter setae behind it weak, g only slightly longer and thicker than anterior peristomal setula; vi very long and robust, often as long as vti; peristomal setulae sparse (4 or 5) and those posterior about as long as 2 small postgenal setae; postocular setulae shorter than peristomals but numerous, in single long row. Eye subcircular (8:7), but somewhat tapered ventrally, with longest diameter 3–3.3 times as long as smallest genal height. Gena ( Fig. 119 ) higher than in relatives except for P. vlasovi . Antenna with scape and 1 st flagellomere more or less paler than (usually) blackish pedicel; 1 st flagellomere brown to dark brown, relatively short, subovoid, with whitish ciliation on apex ( Fig. 124 ) longer than in P. fenestralis and relatives. Arista relatively long, about 4.4 times as long as antenna, with ciliation ( Fig. 123 ) dense and longer than in all other congeners under study.

Thorax largely dark brown ( Fig. 119 ) and brown to golden brown microtomentose ( Fig. 124 ); mesonotum subshining, pleuron duller. Sutures between humeral callus, notopleural area, mesonotum and pleural sclerites pale brown to ochreous-yellow or the whole notopleuron pale ( Fig. 119 ). Scutellum shorter than in relatives, nearly twice wider than long, flat on disc, rather subcircular ( Fig. 124 ). Thoracic chaetotaxy (cf. Figs 119, 121, 124 ): mesonotal macrosetae long and some robust; 1 hu (only as long as posterior npl) and 2 microsetae on humeral callus (that more medial twice longer); 2 relatively long npl (anterior unusually long, twice longer than posterior, see Fig. 124 ); 1 distinct prs (as long as hu) and 1 much shorter sa; 2 pa, the outer very long, as long as or longer than dc, the inner short, as long as sa; only 1 long and robust dc in prescutellar position but 4 dc microsetae (in front of dc) distinctly enlarged, twice longer and thicker ac microsetae); 8 rows of ac microsetae on suture but only 4 (less often 6) in front of scutellum; prescutellar ac microsetae (or only medial pair) usually somewhat longer but not thicker than other ac microsetae; 2 very long and robust sc, laterobasal (longest thoracic seta) slightly to distinctly longer than apical ( Fig. 124 ); only 1 long and robust posterior stpl (as long as dc, Fig. 119 ), anterior stpl reduced to fine microseta or absent.

Legs largely dark brown (coxae, femora, tibiae), with brown to pale brown trochanters, knees, apices of tibiae and tarsi ( Fig. 119, 121 ). Pedal chaetotaxies: f 1 with 3 erect setae in posterodorsal row, and with 3 or 4 longer setae in distal three-fifths in longer posteroventral row. f 2 anteriorly with 1 robust and long subapical seta and 1 short seta in front of it, and posteriorly with 1 short curved posteroapical seta. t 2 ventrally (see Figs 138, 140 ) with only 1 long robust subapical (diverging from axis of tibia) seta considered to be a distally shifted vpa and 1 small av seta near middle; dorsally ( Fig. 139 ) with setosity very similar to that of P. fenestralis and relatives but above 1 long proximal posterodorsal seta there is 1 small additional seta (thus as in P. tenebricus ) and there is only 1 small posterior seta in about proximal two-fifths ( Figs 138, 139 ); apex of t 2 provided with 2 short (1 longer, 1 small) subapical setae anteriorly ( Fig. 140 ) but with a group of small setae posteriorly ( Fig. 138 ) unlike all other relatives. f 3 with 1 short and weak anterior subapical seta; t 3 with ventroapical setula stronger and more distinct than in other Pteremis species. Other parts of femora and tibiae uniformly finely setulose. Mid basitarsus (mt 2) almost always with 1 enlarged ventral setula ( Figs 138, 140 ). Ratio t

2

: mt

2

= 1.90–2.12.

Wing absent, only small scale-like tegula with 3 marginal setulae retained (cf. Fig. 124 ). Haltere entirely missing, with no remnant preserved.

Abdomen blackish brown to black, but dorsally with golden brown microtomentum (cf. Fig. 124 ) and rather subshining ventrally. Dorsal side of abdomen strongly convex ( Fig. 119 ) of ovoid to elongately ovoid outline (cf. Fig. 121 ), widest at 3 rd segment and being similar both in male and female. T2–T5 more densely but shortly setose than in relatives, with only setae at posterior margins longer and more robust but those in posterior corners not markedly longer (cf. Fig. 132 ). In contrast to other Pteremis species, T1+2 is not the largest abdominal tergum, being as long as (or slightly shorter than) T4 but strongly narrower anteriorly, widest at posterior margin; T3 widest and most transverse sternum but shorter than T4 or T1+2; T4 slightly narrowed posteriorly (distinctly less than T1+2 is anteriorly); T5 markedly shorter and narrower than T4 and posteriorly strongly tapered, transversely rounded trapezoidal. Preabdominal sterna also strongly convex: S1+2 smallest, transversely trapezoidal, strongly narrowed anteriorly, pale brown (lightest anteriorly) but with posterior marginal area darkened, blackish brown. S3 and S4 distinctly shorter and much narrower than adjacent terga but similarly blackish brown to black, with sparser and finer short setae; S3 slightly tapered anteriorly and smaller (shorter and narrower) than S4, the latter distinctly largest (widest and longest) sternum. S5 ( Fig. 131 ) short, only about half length of S4 and also shorter than S3, more transverse than in other congeners, with twice emarginated posterior margin on both sides of posteromedial comb of spines; this comb short (narrow) and composed of fine apically blunt spines. Posteromedial membranous area in front of this comb relatively small but somewhat protruding posteriorly, very finely micropubescent. Lateral parts of sternum simply setose, with longest and unusually robust setae in row at posterior margin; no group of curved setae at lateral margin of posteromedial membranous area, there is a single seta on each side instead. S6+7 and S8 formed as in other Pteremis species but original S7 with posteroventral projection dark-pigmented; S6+7 with setae in both pairs finer and more distant; S8 bare, without a pair of small dorsal setae.

Genitalia. Epandrium ( Figs 125, 126 ) of medium length and width, somewhat asymmetrical dorsally in caudal view ( Fig. 125 ), with rather uniform and robust setae, those posteroventral somewhat longer than others. Anal fissure elongately suboval, yet narrower than that of P. fenestralis . Cerci large and long ( Fig. 125 ), each distally narrowed, flattened and bare as that of P. tenebricus but its flat apex bent posteriorly (see Fig. 126 ). Medandrium as in most relatives. Hypandrium with anteromedial apodeme short, strongly asymmetrical as usual, but directed more dorsally ( Fig. 126 ). Gonostylus ( Figs 125–129 ) with anterior lobe much larger than posterior. Anterior lobe ( Fig. 127 ) rather compact, anterodorsally with short dark subtriangular process and distinctive setosity (4 short setae plus micropubescence) on outer side ( Fig. 127 ); ventrally with 3 usual robust and long bent setae, and shortened, robust, dark-pigmented posteriorly directed projection and 3 or 4 spinulae between the latter and posterior robust seta; posterolateral oblique longitudinal spinulose ledge narrow but posteroventrally terminated by unique group (comb) of 4 (3 robust, 1 smaller) dark, heavily sclerotized blunt spines ( Figs 127, 129 ) directed medially (see Fig. 125 ). Posterior lobe (separated in Fig. 128 ) narrow, largely hidden behind anterior lobe (in lateral view, Fig. 126 ) terminated by relatively slender spine, 1 fine subapical seta, posteriorly with relatively small subconical process having sinuate, medially directed seta on apex and anterodorsally with 1 unusually robust seta (see Fig. 128 ). Aedeagal complex ( Fig. 130 ) of typically simple Pteremis construction, distinguished from other species by simple phallapodeme without dorsal keel; phallophore yet lower (dorsoventrally shorter) and stouter than that of P. ferreus having relatively blunt apex; distiphallus most dilated in the middle as in some other Pteremis species, but a pair of slender band-like lateral sclerites apically connected ( Fig. 130 ) and dorsolateral sclerite apparently separated from slender and elongate dorsal sclerite. Postgonite distinctly sinuate in lateral view but relatively slender also proximally, and its apex club-shaped although flatter than that of P. fenestralis . Ejacapodeme medium sized, having slightly sinuate distal digitiform process gradually projecting from wider proximal part (see Fig. 130 ).

Female ( Figs 121, 122 ). Head, thorax, legs and preabdomen very similar to those of male unless given otherwise. Total body length (measured with postabdomen retracted) 1.87–2.78 mm. Ratio t

2

: mt

2

= 1.90–2.11.

Abdomen with ovoid, strongly convex preabdomen ( Figs 121 , 132 ) and very long and narrow, telescopic postabdomen (at rest retracted in preabdomen). Preabdominal terga ( Fig. 132 ) very similarly sized and formed as in male, only T5 distinctly longer (as long as or somewhat longer than T3) and strongly posteriorly tapered and rounded; all preabdominal terga somewhat more densely setose ( Fig. 132 ). Preabdominal sterna: S1+2, S3 and S4 formed, coloured and setose as in male but S5 unmodified, as long as or even slightly longer than S4 but much narrower, transversely trapezoidal (strongly tapered posteriorly), with rounded corners.

Postabdomen ( Figs 135–137 ) very slender, elongate, with sclerites pale-pigmented to partly desclerotized, so differing from that of all other known Pteremis species. T6 distinctly longer than broad, slightly narrower anteriorly, pale-brown pigmented only laterally and anteriorly, with short and fine setae in posterior half including 1 longer in posterior corners. T7 also longer than broad, elongately oblong, narrower and shorter than T6, similarly pigmented and setose but setae fewer; T8 about as long as broad, but its lateral parts reaching far ventrally (cf. Fig. 136 ), dorsally with tripartite pigmentation composed of a paler tongue-shaped medial part and larger and darker lateral parts ( Fig. 135 ), both micropubescent except for anterior parts but only lateral parts with 1 longer and a few short fine setae ( Fig. 136 ). T10 narrow, longer than broad, elongately pentagonal, very finely micropubescent and with a medial pair of small setae in posterior third ( Fig. 135 ). S6 similar to T 6 in setosity and pigmented pattern, also elongate but somewhat shorter and narrower posteriorly ( Fig. 137 ). S7 closely resembling T7 but somewhat narrower, or slightly tapered posteriorly ( Fig. 137 ), distinctly smaller and narrower than S6. S8 ( Figs 136 , 142, 144, 145 ) elongate, narrower than S7, with rounded posterior margin ( Fig. 142 ), thus tongue-shaped but normally with posterior third or two-fifths upcurved dorsointernally ( Figs 144, 145 ); posterior part of S8 micropubescent, with 1 or 2 lateral setae, and posteromedially with a group of 6–8 (4 or 6 very short, 2 long sinuate) setae, all on elevated sockets. S10 (in largest extension) somewhat shorter but wider than S8, also longer than broad ( Fig. 141 ), posteriorly narrowed and rounded, almost completely micropubescent and with rather rich setosity, including several long but fine marginal setae; anterior margin of S10 sinuately emarginate ( Fig. 141 ). Spectacles-shaped sclerite submembranous, represented by a pair of rather large ovoid but often distorted rings ( Fig. 143 ). Spermathecae 2+1 ( Figs 133, 134 ) unique by combining characters known in several other species: elongately pyriform, having main body (ball-shaped to broadly ovoid) separated from conical bases by 2 or 3 incomplete rings but conical bases densely overgrown by short, blunt, dark and curved spines; terminal parts of ducts long, well-sclerotized and dark-pigmented, and those of paired spermathecae connected far from body of spermathecae ( Fig. 134 ) though not so far as in P. fenestralis . Cerci ( Figs 135, 136 ) relatively small, moderately broad but somewhat dorsoventrally flattened (see Fig. 136 ), micropubescent, setose as in most other Pteremis species, including 2 long sinuate setae (dorsopreapical shorter than apical).

Etymology. The species name is derived from Apterina Macquart, 1835, a genus of Copromyzinae (currently a synonym of Crumomyia Macquart, 1825 ), to refer to aptery of the new species. It is a Latin noun in the nominative singular standing in apposition.

Comments. Pteremis apterina sp. nov. is (together with P. vlasovi , see below) externally most dissimilar to other species of the genus Pteremis . Apart from the entire aptery, it is also characterized by pvt absent, scutellum shortened and with very long laterobasal sc seta ( Fig. 124 ), long and robust, distally shifted vpa ( Fig. 140 ) on t 2 and strongly convex preabdomen and very narrowed female postabdomen ( Fig. 142 ). However, apart from the modified female postabdomen, the structures of male and female terminalia generally resemble those of other congeners. As discussed above, it can be more related to P. pulliceps , P. canaria and P. ferreus than to P. fenestralis , mainly because of the spermatheca with surface rings separating the basal conical part from the distal ovoid main body ( Fig. 133 ).

Pteremis apterina also differs from all congeners in a number of features in the male terminalia, including male S5 with projecting posteromedial comb of spines ( Fig. 131 ), male cercus with flattened apex bent posteriorly ( Fig. 126 ), anterior lobe of gonostylus with longitudinal spinulose ledge terminated by a group (comb) of 4 heavily sclerotized blunt spines ( Figs 127, 129 ) and distiphallus with slender band-like lateral sclerites apically connected ( Fig. 130 ). Also, its unusually long and slender female postabdomen is characterized by a number of features, including all sclerites elongated and often partly depigmented ( Figs 135, 137 ), tongue-shaped S8 ( Fig. 142 ) normally dorsointernally upcurved ( Figs 144, 145 ), S10 with anterior margin sinuately emarginate ( Fig. 141 ) and spermathecae with conical bases densely overgrown by blunt, dark and curved spines ( Figs 133, 134 ).

Biology. This wholly apterous species is associated with the leaf litter stratum, probably originally in laurel forests (Laurisilva) of Azores, as found by means of pitfall trapping in Caldeira de Serra de Santa Bárbara in Terceira I. and by sifting leaf detritus under laurel trees in São Miguel I. ( Fig. 148 ). However, material obtained by pitfall traps operated in Santa Maria I. shows that it now can also be abundant in exotic forest plantations. The habitat in the type locality at Lagoa verde near Sete Citades ( Fig. 146 ) is also mostly secondary forest with only remnants of laurel trees preserved ( Fig. 147 ).

Distribution. Azores: Terceira I. ( Ilha Terceira), São Miguel I. (Ilha de São Miguel, type locality), Santa Maria I. (Ilha de Santa Maria). Because it is wholly wingless, P. apterina is surely endemic to the Azores. However, its presence on three different islands (distance between São Miguel I. and Santa Maria I is ca 80 km, distance between São Miguel I. and Terceira I. is ca 135 km) seems to be peculiar and in need of explanation. Because there is no distinct morphological difference between specimens from these three island populations it is improbable they arose simultaneously and independently from a common winged ancestor three times. It is more likely that the species originated on only one of these islands and has been relatively recently introduced (as apterous adults or larvae) to other islands, e.g. via transport of forest detritus when planting trees during reforestation.

Figures

Figs 119–124. Pteremis apterina sp. nov. 119 – male, holotype, left laterally; 120 – labels of the holotype; 121 – female, paratype, dorsally; 122 – ditto, left laterally; 123 – head of the male paratype, frontally; 124 – head and thorax of the same specimen, dorsally. Scales = 0.5 mm. Photo by M. Deml (119, 121, 122) and J. Roháček (others).

Figs 125–131. Pteremis apterina sp. nov., male, paratype (São Miguel I., Sete Citades). 125 – external genitalia, caudally (aedeagal complex and left gonostylus omitted); 126 – ditto, left laterally; 127 – anterior lobe of gonostylus, left laterally; 128 – posterior lobe of gonostylus, left laterally; 129 – posteroventral part of anterior lobe of gonostylus, left laterocaudally; 130 – aedeagal complex, laterally; 131 – male S5, ventrally. Scales = 0.05 mm (Figs 125–130), 0.1 mm (Fig. 131).

Figs 132–137. Pteremis apterina sp. nov., female, paratype (São Miguel I., Sete Citades). 132 – whole abdomen, dorsally; 133 – single spermatheca; 134 – paired spermathecae; 135 – postabdomen, dorsally; 136 – ditto, laterally; 137 – ditto, ventrally. Scales = 0.2 mm (Figs 132, 135–137), 0.05 mm (others).

Figs 138–145.Pteremis apterina sp. nov., male and female, paratypes. 138 – male left t2 and mt2 posteriorly; 139 – ditto, dorsally; 140 – ditto, anteriorly; 141 – female S10, ventrally; 142 – female S8 (unfolded), ventrally, 143 – spectacles-shaped sclerite, ventrally; 144 – female S8 (with posterior part incurved), ventrally; 145 – ditto, laterally. Fig. 142 based on paratype from Santa Maria I., others on paratypes from São Miguel I. Scales = 0.2 mm (Figs 138–140), 0.05 mm (others).

Figs 146–148. Pteremis apterina sp. nov., type locality and habitats. 146 – type locality at Lagoa verde near Sete Citades (Azores: São Miguel I.), with collecting sites (arrows); 147 – lush forest, habitat in the type locality; 148 – leaf litter in laurel forest near Caldeira Velha, microhabitat of the species. Photo by J. Roháček.