Sisyrnodytes irwini Oldroyd, 1974

Londt, Jason G. H., 2009, A review of Afrotropical Sisyrnodytes Loew, 1856 (Diptera: Asilidae: Stenopogoninae), African Invertebrates 50 (1), pp. 137-137 : 155-157

Sisyrnodytes irwini Oldroyd, 1974

Figs 21, 22 , 44

Sisyrnodytes irwini: Oldroyd 1974: 73 ; 1980: 368 (catalogue).

Redescription:

Male (based on holotype in good condition; the first three abdominal segments are glued to a card and pinned below the specimen along with a micro-vial containing the macerated genitalia).

Head: Dark red-brown, blackish setose. Antennae: Dark red-brown except for tip of style which is yellowish. Scape and pedicel blackish setose. Major ventral setae of pedicel shortish, projecting to about halfway along postpedicels. Basal element of style short (only slightly longer than broad). Eye to face width ratio 1.8:1. Mystax of moderate length, blackish. Frons and vertex blackish setose. Laterally situated frontal setae not extending below antennal sockets. Occipital and postocular setae blackish. Palps and proboscis blackish setose.

Thorax: Dark red-brown, blackish setose. Pronotum dark red-brown setose. Mesonotum entirely setose except for narrow paramedial strips and sutural and postsutural spots. Scutellum apruinose with poorly defined transverse groove (has crinkled appearance); disc asetose, 12 dark red-brown apical setae. Pleural setae dark red-brown. Katepimeron asetose, katatergals long, shafts more or less smooth. Legs: Dark red-brown, mainly blackish setose (there are some small yellowish setae ventrally on tibiae and tarsi). Claws longish, dark red-brown; empodia longish yellowish, pulvilli small but clearly evident. Wings 3.5× 1.5 mm. C black setose basally; membrane pale brownish stained except for distal third of wing. Haltere with orange-brown stalk and yellow knob.

Abdomen: Dark red-brown; short blackish setose (slightly longer laterally).

Genitalia ( Figs 21, 22 ): Epandrium greatly reduced and simple in structure, proctiger extending well beyond it. Gonocoxite with fairly long external lobe tapering to broadly rounded tip, internal lobe long and fairly slender. Gonostylus long and slender. Hypandrium much flattened dorsoventrally, triangular in ventral view, with medial lobe extending almost as far as internal lobe of gonocoxite. Aedeagus robust with blunt tip.

Female: Similar to male but displaying some sexual dimorphism. Females (previously unrecorded) are never entirely dark red-brown setose, but always have some pale yellow and a few orange setae (not commonly).

Variation:Wing length ơ 3.1–4.4 mm, ^3.1 –4.6 mm.A fairly uniform species displaying some geographical variation in setal coloration. Males may be entirely dark red-brown setose like the holotype (i.e. those in the southern parts of the distribution) or possess some white or yellow setae (i.e. those in the northern parts of the distribution) on head and thorax (i.e. dorsal part of mystax, frontals, some postoculars, some pronotals, all mesonotals, all apical scutellars, anepisternals, proepimerals). While the mystax may be entirely red-brown it is usually pale yellow, but may have a few dark red-brown and white setae as well. The pronotum, mesonotum, scutellum and all pleura, including katatergite, are yellow setose.A few females may have some yellow leg setae and even a few yellow abdominal setae laterally. The extent and intensity of wing staining are variable. Those with darker staining frequently have small areas involved.

Holotype (examined): ơ SOUTH AFRICA: Northern Cape: ‘South Africa, Cape Prov / 2 mi. [c. 3.2 km] SW. Brandkop [31°16'S: 19°10'E], 1300 ft / Sept. 12, 1972, 3119Ac / ME&BJ. Irwin, Stream bed’, ‘ Sisyrnodytes / irwini sp. n. / det. H. Oldroyd 1972 / Holotype’ [white] (NMSA). Note: Oldroyd (1974) records: ‘Type in Pietermaritzburg. Type-locality: Cape Province, 38 km S.W. Brandkop (Irwin).’ The conversion from imperial to metric units being incorrect (2 miles = 3.2 kilometres).

Other specimens examined: NAMIBIA: 1 ơ 3^‘ Namibia 60km S. Aus / 2716AB 1.ix.1983 / Londt & Stuckenberg / Broken veld at base / of small hill’ ( NMSA) . SOUTH AFRICA: 2 ơ 1^‘ Sth Africa: Cape Prov / Richtersveld 2816BD / 40km S of Ochta Mine / Londt & Stuckenberg / 2.ix.1983 / Mixed Karoo / bush with few flowers’ ( NMSA) ; 6 ơ 2^‘ Sth Africa: Cape Prov / Augrabies Falls Nat. / Park 8.ix.1983 / 2820CB B Stuckenberg / & J Londt Rockery & sandy areas in Camp’ ( NMSA) ; 2 ơ ‘ Sth Africa: Cape Prov / Richtersveld 6km W / of Kuboes 1.ix.1989 / 28°27'00''S: 16°59'30''E / B Stuckenberg J Londt / P Croeser 200m Sandy / area with succulents’ ( NMSA) ; 1^‘ Onseepkans [28°45'S: 19°17'E] / nr Orange Riv / Bushmanland’ ~ ‘ Mus Staff / Oct. 1959 ’ ( SAMC) ; 1 ơ ‘ Pofadder [29°08'S: 19°23'E] / Bushmanland’ ~ ‘ Mus. Staff / Oct. 1939 ’ ( SAMC) ; 3 ơ 3^‘ Naib [29°21'S: 18°20'E] or / Bushmanland / Btw Springbok / and Pella’ ~ ‘ Mus Staff / Oct. 1939 ’ ( SAMC) ; 1^‘ Sth Africa: Cape Prov / 2km NE of Carnarvon / 14.xi.1986 3022CC / Londt & Quickelberge / 1350m Flat scrubland’ ( NMSA) ; 1 ơ ‘ Cape Prov / 7km N / Brandvlei [30°27'S: 20°29'E] / VB Whitehead’ ( SAMC) ; 1^‘ Sth Africa: Cape Prov / 5km SE of Middelpos / 3120CC 17.xi.1986 / Londt & Quickelberge / 1190m Dry scrubland’ ( NMSA) ; 1 ơ ‘ Thee Kloof [32°06'S: 20°42'E] / Fraserburg C.P. ’ ~ ‘ Mus Staff / Nov. 1935 ’ ( SAMC) ; 1^‘ Dikbome / Merweville [32°40'S: 21°31'E] / Koup / C.P.’ ~ ‘ Mus. , Expd. , / Oct. 1952 ’ ( SAMC) ; 1^‘ Willowmore [33°17'S: 23°30'E] / – Vonderling / C.P.’ ~ ‘ Mus., Expd. , / Oct. 1952 ’ ( SAMC) ; 1 ơ ‘ Gamka’s Poort [33°19'S: 21°43'E] / C.P.’ ~ ‘ Mus., Expd. , / Oct. 1952 ’ ( SAMC) ; 1 ơ 1^‘ Rooinek Pass [33°20'S: 20°55'E] / C.P.’ ~ ‘ Mus., Expd. , / Oct. 1952 ’ ( SAMC) ; 1 ơ ‘ Sevenweeks Poort / Rooinek Pass / C.P.’ ~ ‘ Mus. , Expd. , / Oct. 1952 ’ ( SAMC) .

Distribution, phenology and biology: Found fairly widely distributed within the succulent Karoo and Nama-Karoo biomes of southern Africa ( Fig. 44 ), the species appears to favour arid places with sandy ground, succulents and scrub vegetation. It is active in the adult phase during spring and early summer (September–November) (Table 1). Data suggest that population levels may be locally low.

Similar species: This species is fairly distinctive and should not be confused with others. It is small, has a predominantly blackish mystax and small but visible pulvilli.

Figures

Figs 19–24. Sisyrnodytes species, ơ terminalia: (19, 20) S. dasykylon sp. n., 23 km SE of Middelpos paratype, lateral and ventral; (21, 22) S. irwini Oldroyd, 1974, holotype, lateral (shape of robust aedeagus shown with a broken line) and ventral; (23, 24) S. major Adams, 1905, Nguruma, Kenya, lateral and ventral. Scale lines = 1 mm.

Fig. 44. Distribution of Sisyrnodytes aethes sp. n. (•), irwini Oldroyd, 1974 (·) and vestitus Oldroyd, 1974 (9).