186 Florida Entomologist 86(2) June 2003 THE GENUS RHOPALOSYRPHUS (DIPTERA: SYRPHIDAE) HOWARD V. WEEMS, JR.1, F. CHRISTIAN THOMPSON2, GRAHAM ROTHERAY3 AND MARK A. DEYRUP4 1(retired) Florida State Collection of Arthropods, P.O. Box 2309, Hawthorne, FL 32640-2309 2Systematic Entomology Laboratory, USDA, NHB-168 Smithsonian Institution, Washington, D.C. 20560 3Department of Natural History, Royal Museum of Scotland, Chambers Street, Edinburgh, EH1 1JF Scotland 4Archbold Biological Station, P.O. Box 2057, Lake Placid, FL 33862 ABSTRACT The flower fly genus Rhopalosyrphus Giglio-Tos (Diptera: Syrphidae) is revised. The genus is redescribed; a key to species is presented; the phylogenetic relationships of the genus and species are hypothesized; the included species are described; with new species, R. ramu- lorum Weems & Deyrup, described from Florida (type) and Mexico; R. australis Thompson from Brazil and Paraguay (type); and the critical characters are illustrated. Key Words: taxonomy, identification key, neotropics, nearctic RESUMEN El género de la mosca de la flor del género, Rhopalosyrphus, (DIPTERA: Syrphidae) es revi- sada y es redescrito; se presenta una clave para las especies; la relación filogenética del gé- nero y las especies es formulada; las especies incluidas son descritas; con las nuevas especies, R. ramulorum Weems & Deyrup, descrita de Florida (tipo) y México; R. australis Thompson de Brasil y Paraguay (tipo); y los caracteres críticos son ilustrados. Translation provided by author. Rhopalosyrphus Giglio-Tos is a small group of Giglio-Tos 1892b: 34 [journal (1893: 130] (descrip- microdontine flower flies restricted to the New tion); Aldrich 1905: 347 (catalog citation); Kertész World subtropics and tropics, ranging from south- 1910: 360 (catalog citation); Hull 1949: 312, figs. ern United States to northern Argentina. These (description, figures of habitus, head, abdomen, flies are rarely collected, only some two dozen hind leg); Capelle 1956 (review, key); Cole & specimens are known. The adults mimic eume- Schlinger 1969: 307 (descriptive notes); Thomp- nine vespids, such as Zethus, which nest in twigs son et al. 1976: 60 (catalog citation); Vockeroth & (Bohart & Stange 1965). The immature stages are Thompson 1987: 729 (key reference). known for only one species. These were found in Holmbergia Lynch Arribálzaga 1891: 195. ant nests (Pseudomyrmex) in twigs and grass Type species, guentherii Lynch Arribálzaga culms, where the larvae probably prey on ant (monotypy). Synonymy by Giglio-Tos (1892a). brood. The genus contains only three species. One Head: face convex, produced anteroventrally, wide ranging species, R. guentherii, is found from pilose; gena small, linear, pilose; frontal promi- southwestern United States to northern Argen- nence absent, antenna inserted above middle of tina. The others are more restricted in their head; frons short, about ¼ as long as face, as wide ranges; R. ramulorum, presently known from a as face (&) or slightly narrowed dorsally ((), pi- few specimens from Florida and Mexico, and R. lose; vertex broad, about 3 times as long as frons, australis from southeastern Brazil, Peru and Par- as wide as frons, not swollen, pilose and punctuate; aguay. The genus is here revised, with complete ocellar triangle small, equilateral, well separated synonymies, descriptions, and distributional and from eye margins; occiput broad on dorsal ⅓; eye biological data given for all taxa. Adult terminol- bare, dichoptic in male. Antenna elongate, longer ogy follows Thompson (1999), larval terminology than face; scape and basoflagellomere elongate, at follows Hartley (1961) and Rotheray (1991). least 4 times as long as pedicel; scape about 6 times as long as broad; arista bare, inserted baso- GENUS RHOPALOSYRPHUS GIGLIO-TOS laterally on mesal surface, about as long as scape. Thorax: longer than broad; postpronotum pi- Rhopalosyrphus Gilgio-Tos 1891: 3. Type spe- lose; meso-anepisternum with anterior portion not cies, Holmbergia guentherii Lynch Arribálzaga differentiated, uniformly pilose; meso-katepister- (subsequent monotypy, Giglio-Tos 1892a: 2). Willis- num completely pilose; meso-anepimeron with ton 1892: 78 (catalog citation, descriptive note); posterior portion bare; meropleuron with barrette Weems et al.: Genus Rhopalosyrphus (Diptera: Syrphidae) 187 pilose; metasternum developed, pilose (although odon, sensu lato is unresolved: Rhopalosyrphus reduced in some species); scutum punctuate, with shares with the Microdon clade the bifid aedeagus appressed pile; metatibia expanded apically; and appears closely related to Ceriomicrodon. Ce- scutellum with or without small apical calcar, riomicrodon shares characters 3, 4, 5, 6, 7, 8 and without distinct ventral pile fringe. Wing: brown its abdominal shape could be considered derived on anterior 1/3, extensively microtrichious; mar- from that of Rhopalosyrphus. The two differ only ginal cell broadly open; stigmatic crossvein by the presence of pile on the meropleuron. present; vein M1 with apical portion straight, Microdon aurcinctus, described by Sack (1921: joining vein R4+5 perpendicularly; vein M2 138) in Rhopalosyrphus, belongs to the Pseudomi- present or absent; vein R4+5 with spur. crodon group of Microdon. The species of this Abdomen: petiolate; 1st segment short; 2nd group differ from Rhopalosyrphus in the charac- segment as broad as thorax basally, but con- ters listed above and in having the vertex swollen stricted, cylindrical apically; 3rd segment cylin- and shiny. drical; 4th and 5th segments forming a compact Based on puparial characters, the immature club; aedeagus bifid. stages of Rhopalosyrphus closely resemble Micro- Puparium: elongate with broader ventral than don. They both have the anterior end consisting of dorsal surface; marginal band of variously-sized the metathorax, with the prothorax and mesotho- setae; dorsal surface flat; ventral surface convex; rax hidden beneath it, a marginal band of setae marginal band notched anteriorly; prothorax and which surrounds the puparium except for a notch mesothorax hidden beneath metathorax; mandi- at the anterior end, sharply-pointed antennomax- ble with serrate ventral margin. illary organs and mandibles with a serrated ven- Rhopalosyrphus belongs to the subfamily Micro- tral margin. dontinae and is the sister group of Ceriomicrodon The very distinctive shape of the puparium of Hull, together these taxa are the sister group of Rhopalosyrphus separates it from that of Micro- Microdon Meigen, sensu lato. Rhopalosyrphus is don: it has a curved ventral surface that is defined (synapomorphy) by its 1) abdominal struc- broader than the narrow, flat dorsal surface. Also, ture and 2) pilose meropleuron. Other diagnostic the whole structure is elongate rather than oval characters are 3) antenna elongate, longer than in outline. The reverse appears in Microdon, with face, usually about twice as long; 4) scape and ba- the dorsal surface being broader and curved and soflagellomere elongate; 5) face produced ven- the ventral surface narrower and flat. These dif- trally; 6) occiput greatly developed on dorsal 1/3; 7) ferences in shape suit the larva to life in hollow metasternum developed, not reduced; and 8) twigs and grass culms in which its prey, larvae metatibia flared apically. The relationship to Micr- and pupae of the ant, Pseudomyrmex, live. KEY TO SPECIES OF RHOPALOSYRPHUS 1. 3rd tergum short, about 1/3 as long as 2nd; 2nd tergum elongate (Fig. 9); eye with an area of enlarged om- matidia medially and posterior to antenna . australis — 3rd tergum elongate, as long as 2nd; 2nd tergum not greatly elongate posteriorly (Fig. 10); eye without en- larged ommatidia . 2 2. Alula completely microtrichose; cell R extensively microtrichose, bare only on basoposterior 1/4 or less; metasternum appearing bare, with pile greatly reduced; face and anepisternum partially black pilose . ramulorum — Alula bare basomedially; cell R completely bare behind spurious vein; metasternum with long, distinct pile, not reduced; face and anepisternum entirely white pilose guentherii Rhopalosyrphus guentherii Lynch Arribálzaga Rhopalosyrphus carolae Capelle 1956: 174 A* Figs. 10-13 (& Arizona, Huachuca Mts., Sunnyside Canyon (HT & UKaL). Byers et al. 1962: 168 (HT UKaL); Holmbergia güntherii Lynch Arribálzaga Wirth et al. 1965: 599 (catalog citation); Cole & 1891: 198, Fig. 3 (habitus) Argentina, Buenos Schlinger 1969: 307 (descr. note, distr. western Aires (T & MACN lost?). Giglio-Tos 1892a: 2 N.A.); Thompson et al. 1976: 60. NEW SYNONYM (notes), 1893: 131 [sep. 35], pl. 1, Figs. 10, 10a-b Wing length: 8.8 mm (()-10.5 mm (&). Head: (description, figures of abdomen, wing); Aldrich brownish black, yellowish white pilose; occiput 1905: 347 (catalog citation); Kertész 1910: 360 grayish white pollinose on ventral 2/3, shiny dor- (catalog citation); Fluke 1957: 36 (catalog cita- sally; eye with ommatidia of more or less equal tion); Capelle 1956: 172, Fig. 2 (description, syn- size; antenna brownish black except orange basal onymy, key reference, figure of head); Thompson 1/3 of scape, about twice as long as face; antennal et al. 1976: 60 (catalog citation). ratio 5: 1: 8. 188 Florida Entomologist 86(2) June 2003 Thorax: brownish black; pleuron silvery-white Counties], Huachuca Mts, Sunnyside Canyon, 9- pilose; scutum brown pilose medially, silvery VII-1940, DE Hardy (allotype (, UKaL). TEXAS: white pilose anteriorly, along transverse suture, Hidalgo Co: Pharr, 23-VI-1947 (1 & USNM); La laterally and posteriorly; scutellum silvery white Joya,