Argyrochlamys Lamb

SCOTT E. BROOKS, 2005, Systematics and phylogeny of Dolichopodinae (Diptera: Dolichopodidae), Zootaxa 857, pp. 1-158 : 38-43

Genus Argyrochlamys Lamb

( Figs. 6 A–E, 7A–E)

Argyrochlamys Lamb, 1922: 391 . Type species: Argyrochlamys impudicus Lamb [Palaearctic, Afrotropical, Oriental], by monotypy.

Halaiba Parent, 1929a: 56 . Type species Halaiba cavicola Parent [Palaearctic, Afrotropical], by monotypy. syn. nov.

Camptoneura Parent, 1930b: 110 . Type species: Camptoneura decolor Parent [Palaearctic, Afrotropical, Oriental], by monotypy [= Argyrochlamys impudicus Lamb ]. Preoccupied by Camptoneura Fieber 1858 ; synonymized by Dyte (1975).

New Combinations. The following new combinations are hereby established: Argyrochlamys breviseta ( Parent, 1939) comb. nov. ( Halaiba ); Argyrochlamys cavicola ( Parent, 1929a) comb. nov. ( Halaiba ).

Recognition. Species of Argyrochlamys can be distinguished by their dull, non­metallic, pale yellowish­brown to dark gray color and strongly medially offset fifth pair of dorsocentrals. Males can be further distinguished by the distinctive comma­shaped or bifurcate projection near the joint of the hind tibia and basitarsus. Females can be further distinguished by their distinctive terminalia with T10 acutely V­shaped and usually with a pair of well­developed rod­like apical projections on T8 that typically protrude from the abdomen.

Description. Body non­melallic, pale yellowish­brown to dark gray. Setae of head, thorax and legs entirely or mainly dark to mainly or entirely pale. Head: Slightly to distinctly wider than high in frontal view. Vertex not excavated, 1–2 pairs of strong vertical setae, stronger than postverticals. Frons and face broad in both sexes. Frons about 1.5–3.4 x wider than high, sides weakly convergent anteriorly. Face weakly narrowing below or parallel­sided. Clypeus slightly produced, wider than high, lower margin straight, ending above or at level of lower eye margin. Palp ovoid with weak setae on outer surface, with or without 2–3 stronger apical setae. Antenna: Scape short, subconical, with weak to distinct medioventral process, dorsal surface with only a few setae; pedicel short, marginal setae often stronger ventrally; first flagellomere ovoid to subtriangular, often longer in male; arista dorsal to apical, normally developed or very short and thick (e.g., male A. breviseta ), 2­segmented, second segment bare. Uppermost postocular setae stronger than lower setae. Postvertical setae subequal or stronger than uppermost pair of postoculars.

Thorax: Broad, acrostichals biserial; 6 dorsocentrals, fifth pair strongly offset medially; 1 strong outer posthumeral, 1 weaker inner posthumeral; 2 notopleurals; 1–2 presuturals, anterior presutural sometimes not differentiated; 1 sutural; 2 supraalars; 1 postalar. Upper part of propleuron with a few to several fine hairs; lower part of propleuron with 1 strong prothoracic seta, with or without sparse fine hairs; pleural surface in front of posterior spiracle bare; metepisternum bare. Notum sometimes with flattened region in front of scutellum (e.g., Argyrochlamys sp. 1). Scutellum with 1 strong inner seta on lateral margin, weak outer seta present or absent.

Legs: Pulvilli developed normally on all legs. Midleg: Femur with 1 anterodorsal preapical seta. Hindleg: Coxa with strong lateral seta near or above middle; femur with well­developed setae along anterodorsal surface, 1 anterodorsal preapical seta, with or without distinct anteroventral preapical seta; tibia of male sometimes with distinct bifurcate posteroapical projection (e.g., Argyrochlamys sp. 1); basitarsus distinctly shorter than second tarsomere, with strong basiventral seta, sometimes with 1 strong dorsal seta (e.g., Argyrochlamys sp. 1), male basitarsus often with conavity and elongate comma­shaped projection posterobasally, occasionally absent (e.g., Argyrochlamys sp. 1).

Wing: Hyaline, veins pale. R2+3 usually straight and ending well beyond middle of wing; R4+5 usually curving posteriorly in distal section; distal section of M beyond crossvein dm­cu with strong anterior bend near middle, ending before wing apex, convergent with R4+5; crossvein dm­cu distinctly shorter than distal section of CuA1. Venation of A. impudicus aberrant, with R2+3 short, reaching wing margin just beyond middle; R4+5 running parallel to R2+ 3 in basal section, curving posteriorly to run parallel with costa in apical third; distal section of M with 90° bend beyond middle, strongly curved beyond bend, reaching wing margin distinctly above apex, strongly convergent with R4+5.

Abdomen: Subconical. Male: T6 bare, short, mostly covered by T5; S2–4 weakly sclerotized; S5 mainly membranous, invaginated medially; S6 mainly to entirely membranous; segment 7 forming short peduncle, mostly hidden in normal repose; S8 rounded to subtriangular, setose. Hypopygium ( Figs. 6 A–C, 7A–C): Epandrium 1.7–2.3 x longer than high; foramen positioned laterally, well­separated from base of cerci; basiventral epandrial lobe not developed, basiventral epandrial seta positioned on infolded ventral margin of epandrium; apicoventral epandrial lobe digitiform to bump­like or absent, with 2–3 strong setae. Surstylus bilobed. Ventral lobe digitiform or short and blunt. Dorsal lobe about twice as long as ventral lobe, digitiform, with a strong, sometimes thickened, dorsal seta and several apical setae. Postgonite: anteroventral portion weakly or well­sclerotized, with bifurcate base sitting under sperm pump; posterodorsal portion well­developed, simple or bifurcate. Proctiger brushes absent. Cercus variable, digitiform to oval ( Figs. 6 A, 7A), sometimes very reduced (e.g., Argyrochlamys sp. 1). Hypandrium more or less trough­like, apex sometimes with a pair of well­sclerotized dentiform projections (e.g., A. impudicus , A. cavicola , Figs. 6 A,C, 7A,C), free laterally with membranous connection to epandrium basiventrally; hypandrial apodeme well­developed; hypandrial arms connected to or separated from hypandrium, sometimes with a pair of weakly sclerotized rounded projections apicodorsally (e.g., A. impudicus , A. cavicola , Figs. 6 B, 7B). Sperm pump small; ejaculatory apodeme short, rod­like, apex occasionally dorsoventrally flattened and weakly flared laterally (e.g., Argyrochlamys sp. 1); basal sclerite of sperm pump indistinct. Phallus usually swollen in basal three­quarters (e.g., A. impudicus , A. cavicola , Figs. 6 B, 7B), sometimes slender and finely wrinkled (e.g., Argyrochlamys sp. 1). Female ( Figs. 6 D,E, 7D,E): T6, T7, S6 and S7 undivided, well­sclerotized to nearly membranous; T8 and S8 divided medially, tergite and sternite not fused anterolaterally, T8 usually with well­developed rodlike apical projection extending well beyond base of T10 (e.g., A. impudicus , A. cavicola , Figs. 6 D, 7D), S8 weakly sclerotized. Furca present, rod­like or bifurcate apically. T10 acutely V­shaped, not divided medially, bearing 6–8 spines. Cercus weakly sclerotized, upper lobe digitiform with several short apical setae

Geographical Distribution. Argyrochlamys is recorded from the Afrotropics ( Sudan, Eritrea, Djibouti, Somalia, Ghana, Angola, Seychelles, Mauritius) ( Dyte & Smith 1980; Grichanov 2004) and the Oriental Region (Chagos Island, Sri Lanka) ( Dyte 1975). Dyte (unpublished manuscript) also recorded A. impudicus and A. cavicola from Oman in the southernmost part of the Palaearctic region.

Phylogenetic Relationships. Argyrochlamys forms the sister group to the large clade including Cheiromyia , Paraclius , Pelastoneurus , Platyopsis , Tachytrechus and Metaparaclius based on the curvature of wing vein M (character 34:2). See “ Tachytrechus genus group” section above for discussion of the monophyly of Argyrochlamys .

Remarks. Parent (1929a) placed Halaiba in the Rhaphiinae , based on the shape of the first flagellomere and the apical arista, but noted the presence of setae on the dorsum of the scape and the Paraclius ­like wing venation, suggesting placement in the Dolichopodinae . Ulrich (1981) subsequently transferred Halaiba to the Dolichopodinae based on an examination of the types of both H. cavicola and H. breviseta . My cladistic analysis supports Ulrich’s classification and further indicates a close relationship between the type species of Halaiba and Argyrochlamys based primarily on characters of the male and female terminalia. Argyrochlamys has traditionally been recognized by its aberrant wing venation; however, this feature is an autapomorphy of A. impudicus . I consider Halaiba to be congeneric with Argyrochlamys .

The male genitalia of A. breviseta have a heavily sclerotized, dark, bifurcate, dorsal process that is curved ventrally. Based on my examination of the male syntype, I believe this structure to be the postgonite; however, dissection is required to confirm this interpretation.

Species of Argyrochlamys are restricted to ocean beaches and are usually collected in burrows of ghost crabs ( Ocypode Lamarck , Ocypodidae ). At present, their ecological role within these burrows is unknown.

Material Examined. Argyrochlamys breviseta (Parent) , [AF]: 1ɗ syntype, 1Ψ syntype ( BMNH); Argyrochlamys cavicola (Parent) , [PA, AF]: 1ɗ syntype, 1Ψ syntype ( MNHN); Argyrochlamys impudicus Lamb , [PA, AF, OR]: 1ɗ syntype, 1Ψ syntype, 1ɗ, 1Ψ ( BMNH); 3Ψ ( MZLU); 1ɗ, 1Ψ (LEM); ɗ holotype of Camptoneura decolor Parent ( MNHN); Argyrochlamys sp. 1, [OR, Sri Lanka]: 4ɗ, 5Ψ ( MZLU).

Figures

FIGURE 6. Argyrochlamys impudicus: (A) Male genitalia, left lateral view (external); (B) Male genitalia, left lateral view (internal); (C) Male genitalia, ventral view (postgonite, surstylus and cerci not shown); (D) Female genitalia, dorsal view; (E) Female genitalia, left lateral view.