Microphorella acroptera Melander

Brooks, Scott E. & Cumming, Jeffrey M., 2025, Revision of the Microphorella acroptera species group and establishment of the Microphorella arcana species group (Diptera: Dolichopodidae sensu lato: Parathalassiinae), Zootaxa 5661 (4), pp. 451-503 : 455-460

Microphorella acroptera Melander

( Figs 4–15 , 100 )

Microphorella acroptera Melander, 1928: 88 .

Type material examined. HOLOTYPE ♂ ( Figs 4, 5 ) labelled: “Pullman Wash|30 May 13”; “ TYPE | Microphorella | acroptera| Mel.” [red label]; “ALMelander| Collection| 1961” ( USNM) . PARATYPES: USA: California: Alameda County: Berkeley Hills , 11.iv.1908, E. T. Cresson Jr (2♀, USNM) [apparently not conspecific with M. acroptera ]. Washington: Whitman County: same data as holotype [46°43'53"N 117°10'47"W] (1♀, USNM) ; same data as holotype except, 16.vi.1912 (1♂, 1♀, USNM) ; same locality, date not included on label (1♂, USNM) ; Pullman, Lyle Grove , 3.vi.1919, A.L. Melander (1♂, USNM) .

Other material examined. USA: California: Contra Costa County: Briones Reg. Park [37°57'N 122°08'W], Toyon Canyon, 25.v.1979, D.D. Wilder (1♂, 2♀, CAS) ; Russellmann Park , 2 mi. SE Clayton [37°54'N 121°54'W], 1200 ft, 20.v.1967, P.H. Arnaud, Jr (1♂, 8♀, USNM) . Del Norte County: ca 4.5 mi. NE Gasquet, Eighteenmile Creek , 41°51'21ʺN 123°54'44ʺW, 31. V.2009, S.E. Brooks (1♂, CNC) . Los Angeles County: BYA Harmony Pines Youth Camp , 34°23'21ʺN 117°42'53ʺW, 6–16.vi.2017, veg. along flowing creek, MT, J.H. Skevington (1♂, CNC) . Marin County: Hicks Valley, Arroyo Sausal , W of Point Reyes-Petaluma Rd [38°07'N 122°42'W], 115 m, 18.v.1980, P.H. Arnaud, Jr (5♀, USNM) ; same data except, 14.iv.1984, flight trap in creek bed, 1345–1700 hours (1♀, USNM) ; same data except, 150 m, 12.iv.1987, two flight traps in shaded creek bed ca. 1230–1600 hours DST over water adjacent to Salix sp. (2♂, 1♀, USNM) ; same data except, 115 m, 1.iv.1990, #00191 (1♂, USNM) ; Liberty Gulch nr Alpine Lk. [37°57'N 122°37'W], 640–900 ft, 17.iv.1971, E. Schlinger (1♂, EMEC) ; Lily Lk. nr Alpine Lk. [37°57'N 122°38'W], 680–720 ft, 15.iv.1972, E. Schlinger (1♂, EMEC) . Mendocino County: Angelo Coast Range Reserve [39°43'N 123°39'W], on sand below White House, 31.v.1986 (6♂, 14♀, EMEC) ; No. Cal. Coast Range Pres. , 5 mi. N Branscomb [39°42'N 123°39'W], 27.v.1976, E. Rogers (1♂, EMEC) ; Hwy 128 W Yorkville [38°53'53"N 123°12'52"W], 11.vi.1988, J.A. Downes, 1765/5 (1♂, CNC) . Monterey County: Paraiso Hot Springs , 13 km SW Soledad [36°19'N 121°22'W], 400m, 29.v.1977, P.H. Arnaud, Jr (1♂, USNM) . Napa County: 5.5 km NW Moskowite Corner, Capell Creek [38°29'N 122°14'W], 200 m, 12.vi.1977, P.H. Arnaud, Jr (1♂, CAS) ; Oakville [38°26'N 122°24'W], 180 ft, 25.iv.1971, P.H. Arnaud, Jr, M.M. Arnaud, flight trap in creek bed with flowing water (1♂, USNM) . San Benito County: Cienega de los Paicines , San Benito River [36°43'N 121°18'W], 190 m, 22.vi.1980, P.H. Arnaud, Jr (1♂, USNM) . San Luis Obispo County: S end of Soda Lake , 15 mi. SE Simmler [35°12'N 119°51'W], 2.iv.1969, H.B. Leech (1♂, CAS) . San Mateo County: La Honda [37°19'N 122°16'W], 23.vii.1967, P.H. Arnaud, Jr (2♂, 3♀, USNM) ; same data except, 120 m, 11.vi.1971 (1♀, USNM) ; Redwood City [37°29'N 122°14'W], 29.iii.1952, P.H. Arnaud, Jr (2♂, 8♀, USNM) ; Stanford University, Jasper Ridge Biological Preserve [37°24'N 122°14'W], 9.v.1982, P.H. Arnaud, Jr (2♀, USNM) ; same data except, 22.iv.1990, #00222 (12♂, 5♀, USNM) ; same data except, CNC1155821 (1♂, USNM) ; same data except, 7.v.1995, M. & P.H. Arnaud, Jr, Field Note #01313 (2♀, USNM) ; same data except, 17.iv.1988, P.H. Arnaud, Jr, Townes flight trap near creek bed (1♂, CAS) . Santa Cruz County: Felton, St Cruz Mts [37°03'N 122°04'W], 300–500 ft, 15–19.v.1907, Bradley (3♂, USNM) ; Santa Cruz [36°58'N 122°01'W], 5.iv.1961, R. Brown (1♂, CAS) . Stanislaus County: Del Puerto Canyon, Frank Raines Park [37°25'N 121°22'W], 335 m, 16.v.1970, P.H. Arnaud, Jr (4♂, 2♀, CAS; 1♂, USNM) ; same data except, 17.v.1970 (1♂, 8♀, CAS; 1♀, USNM) . Yolo County: W Sacramento, 4851 Lake Rd [38°34'N 121°34'W], 15.iv.1989, P.H. Arnaud, Jr (1♂, USNM) . Oregon: Curry County: ca 7 mi. E Langlois Floras Crk , 42°54'58"N 124°20'37"W, 29. V.2009, S.E. Brooks, CNC DIPTERA # 105201 (1♂, CNC) ; same data except, CNC DIPTERA # 105202 (1♂, CNC) .

Diagnosis. Males of this species can be distinguished from other members of the M. acroptera species group by the following combination of characters: acrostichal setae absent, or sparse and irregular; hind basitarsus without basiventral spur-like seta; halter brown ( Figs 4 , 6 ); hind trochanter with cylindrical tubercle ( Figs 8, 9 ); face with sides subparallel; hypandrium large and bulbous ( Figs 7 , 11, 12 ); ventral epandrial process with hook-like tip ( Fig. 11 ); right dorsal surstylar lobe thumb-like, bearing blade-like prensiseta laterally ( Fig. 12 ).

Description. Male ( Figs 4 , 6–15 ): Wing length 1.9–2.4 mm. Head ( Figs 4 , 6 ): Mainly blackish-brown pruinose, dark bronze dorsally (concolourous with thorax), ventral part of frons, face and clypeus blackish-brown in anterior view; slightly narrower than thorax in dorsal view; ovoid in lateral view (higher than broad); slightly broader than high in anterior view; larger setae black, smaller setae brown. Ocellar triangle conspicuous. Occiput weakly concave on upper median part. Eyes covered with short ommatrichia; medial edge of eye with small emargination adjacent to antenna; ommatidia subequal in size. Frons about 2× broader than high, widening above. Face linear, about 2× broader than width of anterior ocellus. Face and clypeus blackish-brown with brownish-grey pruinosity, concolourous with ventral part of frons (in anterior view). Clypeus separated from face, small, barely broader than high, slightly widened ventrally, with truncate ventral margin. Setae of head well differentiated (larger dorsal setae similar in size to anterior dorsocentrals): 1 pair of inclinate fronto-orbitals arising slightly ventral to median ocellus; 1 pair of lateroclinate anterior ocellars; 1 pair of small posterior ocellars; 1 pair of inner verticals (sometimes referred to as postocellars); 2 pairs of outer verticals; postocular setae short and uniserial. Antenna ( Figs 4 , 6 ) inserted above middle of head in profile; scape short, funnel-shaped, dark brown; pedicel about 2× longer than scape, spheroidal with subapical circlet of setulae, dark brown; postpedicel about 3× longer than pedicel, about 2× longer than wide, bulb-shaped, blackish-brown, clothed in fine setulae; arista-like stylus apical, 1.6–2× length of postpedicel, blackish-brown, with minute hairs. Palpus dark brown, relatively small, narrowly ovate, about 2.5× longer than wide, with 1 long preapical seta. Proboscis brown, short, projecting ventrally. Gena narrow. Thorax ( Figs 4 , 6 ): Blackish-brown to dark brown pruinose with faint metallic green tinge in lateral view, dorsum dull, dark bronze pruinose with reddish and dark green tinges at certain angles, setae black. Mesoscutum moderately arched, prescutellar depression present. Proepisternum with 2 tiny setae. Postpronotal lobe with a few small setae. Mesonotum longer than wide. Acrostichal setae absent, or sparse and irregularly biserial, usually ending near 2nd pair of dorsocentrals, rarely extending to prescutellar depression; setae on each side of mesonotum: 5–7 dorsocentrals, middle setae weaker, posterior seta longest, 1 presutural supra-alar (posthumeral), 2–3 postsutural supra-alars (sometimes with a couple additional small setae anteriorly), 2 notopleurals, 1 postalar, area laterad anterior dorsocentrals with a few small setae. Scutellum broadly crescent-shaped with 1 long seta per side, rarely with small outer seta present. Mesopleuron bare. Halter brown to blackish brown. Legs ( Fig. 4 ): Slender; dark brown with prominent setae dark brown or black; femora, tibiae and tarsi largely covered with tiny, dark brown setae (paler on medial surfaces); tarsomeres 1–4 of all legs progressively shorter apically with tarsomere 5 slightly longer than 4 and often dorsoventrally flattened; tarsal claws, pulvilli and empodium normally developed on all legs. Foreleg: Coxa with setae on anterior surface, stronger and longer apically; femur and tibia subequal in length, tarsus slightly longer; tarsomere 1 slightly shorter than combined length of tarsomeres 2–5. Midleg: Coxa with a few prominent setae on anterior surface; femur slightly shorter than tibia, tibia and tarsus subequal in length; apex of tibia with 1 strong ventral seta, and often weaker anterior seta; tarsomere 1 slightly shorter than combined length of tarsomeres 2–5. Hindleg: Coxa with 2 prominent setae on lateral surface; trochanter ( Figs 8, 9 ) ventrally with short cylindrical tubercle bearing thick, anteriorly directed, apical spine-like seta and some small adjacent setae, spine-like seta pointed or blunt-tipped, straight or weakly curved; femur, tibia and tarsus subequal in length; femur ( Figs 8, 9 ) weakly bowed outwardly (in dorsal view), with dorsal setae longer and more erect near base, with prominent anteroventral row of setae, setae subequal in length to femur width; tarsomere 1 subequal to combined length of tarsomeres 2–4. Wing ( Fig. 4 , inset): Slightly longer than body (based on non shriveled specimens). Hyaline, veins dark brown, about 2.7× longer than wide. Pterostigma absent, membrane entirely covered with minute microtrichia, alula absent. Costa circumambient. Anterior base of costa with strong dorsal seta and a few shorter proximal setae. Anterior section of costa (between base and R 2+3) with double row of spine-like setae. Posterior section of costa (beyond R 2+3) with setae finer and slightly longer. Radial and medial veins complete and reaching wing margin, CuA+CuP (anal vein) short extending about halfway to wing margin, Sc faint apically. R 1 terminating slightly beyond midpoint of wing and M 2. Base of Rs originating opposite humeral crossvein. R 2+3, R 4+5 and M 1 nearly straight, divergent in basal part, weakly divergent or sometimes subparallel distally beyond base of M 2. M 1 and M 2 divergent.M 2 and M 4 slightly divergent to subparallel beyond cell dm. Costal section between M 1 and M 2 slightly longer than costal section between M 2 and M 4. CuA rounded (convex). Crossvein r-m short. Crossvein bm-m incomplete. Cell dm present, closed by base of M 2 and dm-m crossvein, cell extending to middle of wing. Cells br, bm and cua in basal fourth of wing. Cell cua ovoid. Anal lobe not developed. Calypter with fine setae. Abdomen ( Figs 4 , 6, 7 ): Dark brown with short dark setae (very weak on sternites); segment 7 bare. Segments 5–7 narrowed and laterally compressed to form cavity on right side for hypopygium ( Fig. 10 ). Sternite 5 with broad bilobate ventral projection ( Fig. 10 ), membranous medially, symmetrical with rounded setulose lateral lobes. Sternite 8 subrectangular to rounded, setose, slightly wider than segment 7; tergite 8 vestigial. Hypopygium ( Figs 7, 10–15 ): Concolourous with abdomen; lateroflexed to right; inverted with posterior end directed anteriorly; large, about half as long as abdomen; asymmetrical. Right and left epandrial lamellae narrowly connected dorsally behind cerci. Left epandrial lamella ( Fig. 11 ) shorter than hypandrium and partially overlapping its left side, posterior margin with projecting surstylar lobes and ventral epandrial process, ventral edge broadly rounded and fused with hypandrium but margin distinct; ventral epandrial process articulated at base, basal 2/3 of uniform width, with narrow hook-like tip, medial surface with short dentiform projection near mid-length. Left surstylus divided into dorsal and ventral lobes separated by U-shaped cleft through which left postgonite lobe protrudes. Dorsal lobe of left surstylus with dorsolateral tubercle bearing prominent blade-like prensiseta, subtended by thin medial flap-like lobe with rounded dorsal edge; posteromedially with pair of lobes (hidden behind postgonite lobe), dorsal lobe thumb-like with pair of dorsal setae, ventral lobe globular with 1 basal seta. Ventral lobe of left surstylus projecting medially behind postgonite lobe, as long as dorsal surstylar lobe, digitiform with 5 apical setae (some occasionally with branched tip). Right epandrial lamella ( Fig. 12 ) shorter than hypandrium and partially overlapping its right side, longer than high, ventral edge broadly rounded and fused with hypandrium but margin distinct; ventral epandrial process absent. Right surstylus divided into dorsal and ventral lobes separated by U-shaped cleft through which right postgonite lobe protrudes. Dorsal lobe of right surstylus thumb-like bearing prominent blade-like prensiseta laterally, 2 adjacent lateral setae and 1 medial seta, subtended by thin medial flap-like lobe with rounded dorsal edge. Ventral lobe of right surstylus projecting dorsomedially behind postgonite lobe, similar in length and breadth to dorsal surstylar lobe, with several setae on posterior surface. Hypandrium ( Figs 7 , 11, 12 ) reniform, large, longer than epandrium in lateral view, bare except for pair of short posterior setae. Left postgonite lobe globular basally with bifid apex projected medially (best seen in dorsal view, Fig. 10 ), inner lobe thumb-like, outer lobe tapered to pointed tip ( Fig. 11 ). Right postgonite lobe similar in size and form to left lobe ( Figs 10 , 12 ). Phallus ( Figs 13–15 ) long and convoluted, basal portion tubular with S-shaped double curve giving rise to inflated curve in middle portion, followed by straight, tubular apical portion, apical portion with basal kink, angled to right in posterior view ( Fig. 15 ). Ejaculatory apodeme large, keel-like, with pointed posterior margin and rounded anterior margin (like a bearded axe head). Hypoproct simple, left and right lobes symmetrical, broad and flap-like with a few tiny setae. Cercus membranous and sac-like laterally, sclerotized medially with setose conical mound dorsally and apically tapered process ventromedially, left and right cercus symmetrical (similar to Fig. 38 ).

Female. Similar to male except as follows: Head: Face and clypeus apparently slightly broader, broader than 2× width of anterior ocellus. Legs: Hindleg: Trochanter without tubercle bearing apical spine-like seta; femur without prominent anteroventral row of setae. Abdomen: Apical segments retractable into segment 5. Tergite 5 with cluster of stout medial setae. Terminalia: Tergite 6 with setae on posterior margin unmodified (i.e., not forming prominent row of long, stout setae). Syntergite 9+10 medially divided into hemitergites, with 3–4 acanthophorous spines on each side; cercus sclerotized, pointed apically, with a few short ventral setae.

Distribution and seasonal occurrence. This species as currently recognized, is known from eastern Washington, western Oregon, and northern, central and southern California ( Fig. 100 ). Specimens were collected from March to July.

Remarks. In addition to the types from Pullman, Washington, Melander (1928) mentioned specimens from San Jose and Berkeley Hills, California. The specimens from San Jose were not found in the holdings of the USNM, and the Berkeley Hills specimens, collected by E.T. Cresson Jr on April 11, 1908, are females, which do not appear to be conspecific with M. acroptera . Males from both localities are needed to confirm these distributional records. The specimens from northern California (Eighteenmile Creek) and Oregon (Floras Creek) are less dark in colour, especially on the thorax and halters, than other specimens of M. acroptera , although this could just be an artifact of being critical point dried, unlike most of the other known material. These three specimens have been sequenced and the one from California has a different Barcode Index Number (BIN) than the two from Oregon. The Floras Creek male (CNC DIPTERA 105201) has terminalia that are nearly identical to other M. acroptera , but with a pair of stronger posterior hypandrial setae and a dorsal surstylus prensiseta with a longer narrowly tapered apex. It is therefore possible, that the current concept of M. acroptera includes the presence of additional cryptic species. A photograph of one of the males from Oregon was published in Cumming & Brooks (2022, fig. 28).

The newly described species, M. subacroptera sp. nov. and M. triangulata sp. nov., are apparently closely related to M. acroptera based on their very similar hypopygial morphology.

Figures

FIGURES 4–5. Male holotype of Microphorella acroptera Melander. 4. Habitus, with wing inset (see Fig. 95 for fully labelled wing). 5. Labels.

FIGURES 6–10. Male habitus, hindleg and abdomen of Microphorella acroptera Melander. 6. Habitus (Floras Creek, Oregon, CNC DIPTERA # 105201). 7. Abdomen of same specimen, right lateral view. 8. Hindleg of paratype, posterior view, arrow indicating trochanter tubercle. 9. Hindleg, anterior view (male from Angelo Coast Range Reserve, California), arrow indicating trochanter tubercle. 10. Macerated abdomen (CNC1155821), ventral view, arrow indicating process of sternite 5. Abbreviation: hypd—hypandrium.

FIGURES 11–16. Hypopygium of Microphorella acroptera Melander and M. subacroptera sp. nov. 11. Hypopygium of M. acroptera (CNC1155812), left lateral. 12. Same, right lateral. 13. Phallus and ejaculatory apodeme of M. acroptera (CNC1155834), left lateral. 14. Same, right lateral. 15. Same except, isolated posterior view of phallus. 16. Right dorsal surstylus of M. subacroptera sp. nov. paratype (CNC1155816), lateral view. Abbreviations: cerc—cercus; d sur—dorsal lobe of surstylus; ej apod—ejaculatory apodeme; epand—epandrium; hypd—hypandrium; pgt lb—postgonite lobe; ph—phallus; v epand proc—ventral epandrial process; v sur—ventral lobe of surstylus.

FIGURES 100–101. Known geographical distribution of the Microphorella acroptera species group. 100. Microphorella acroptera Melander and M. convoluta sp. nov. 101. Microphorella bifida sp. nov., M. triangulata sp. nov. and M. tubifera Melander.

FIGURES 36–40. Hypopygium of Microphorella paracroptera sp. nov. 36. Hypopygium (CNC1155811), left lateral view. 37. Same, right lateral view. 38. Same, dorsal view. 39. Phallus (CNC1155809), left lateral view. 40. Same, right lateral view. Abbreviations: cerc—cercus; d sur—dorsal lobe of surstylus; hypd—hypandrium; hyprct—hypoproct; pgt lb—postgonite lobe; ph—phallus; v epand proc—ventral epandrial process; v sur—ventral lobe of surstylus.