Toxomerus costalis (Wiedemann, 1830):140

Toxomerus Macquart, 1855 belongs to Syrphinae (Syrphidae) and it is the only genus included in Tribe Toxomerini, with approximately 150 species described in the world. It occurs mainly in the Neotropical Region with 143 species, followed by the Neartic Region with 16 species (9 endemic) (Borges and Couri 2009).

The genus Toxomerus is characterized by : eye with distinct triangular emargination on posterior margin; gena narrow; arista bare; postpronotum bare; meron bare; anatergum bare; katatergum bare; posterior spiracle with short pile on margin; metasternum bare; metaepisternum pilose; metaepimeron bare; male genitalia well sclerotized, very short to long postanal process arising from fused surstylar apodemes and projecting caudad between bases of surstyli (Borges and Couri 2009).

Toxomerus flaviplurus is a small species (less than 9 mm in lenght), scutum all dark [usually only postpronotum yellow]; scutellum pale pilose; katepisternum withouth dorsal yellow macula or greatly reduced; wing entirely microtrichose, brown to brownish black; pro- and mesofemora black except yellow apical apices; male genitalia greatly enlarged; female abdomen much broader than head.

Adapted from Borges and Couri (2009).

MALE.

Head: Face 1/3 as long as eye width, yellow with black medial vitta, shiny except sparsely white pollinose and pilose laterally; gena black; frontal triangle yellow, white pilose; vertical triangle black, bronze pollinose, black pilose; occiput black, silver pollinose, with thick white pile, with a short row of brownish pile dorsally; antenna yellow to brownish, black pilose, arista brown.

Thorax: Postpronotum yellow to brownish; proepisternum black, white pollinose; proepimeron black; scutum black except yellow laterally after transverse suture, bronze pollinose except for bluish-white pollinose medial vitta, yellow pilose; scutellum usually black, sometimes black with yellow margins, yellow pilose; anterior anepisternum black, long yellow pilose; posterior anepisternum black on anterior 2/3, yellow pilose dorsally, and yellow on posterior 1/3, yellow pilose; katepisternum black, sometimes with a little dorsal yellow macula, dull, yellow pilose; anepimeron black; plumula yellow to brownish, calypter yellow to brownish with brownish fringe except brown fringe on dorsal lobe; posterior mesothoracic pleuron (katepimeron, meron, katatergum, anatergum and postscutellum) black; methatoracic pleuron black; metasternum black, bare; halter yellow. Legs: coxae black, yellow or black pilose; trochanters brown, yellow pilose; femora black, yellow on basal and apical extremities, yellow and black pilose; pro- and mesotibiae yellow, yellow and black pilose; metatibia black, yellow on basal extremity, black and yellow pilose; tarsi brown, black pilose. Wing: brownish, all microtrichose; alula as broad as cell BM appically or as broad as cell C, microtrichose (Fig. 13).

Abdomen: terga yellow and black pilose; 1st tergum all black; 2nd tergum usually black with medial yellow fascia interrupt medially; 3rd to 4th terga black with yellow fascia on anterior 1/3 with sub-lateral triangular projection, sub-medial arcuate projection and medial yellow vitta extending from anterior to posterior brownish fascia; 5th tergum usually black with medial yellow vittae and lateral and posterior yellow maculae. Male genitalia: surstylus very convex laterally and very concave medially, with scattered short setae; postanal process 3/4 as long as surstylus; aedeagus enlarged, proeminent dorsally; superior lobe somewhat quadrangular with short dorsal extension, with pile anteroventrally, with small lobe posterodorsally with pile.

FEMALE.

Similar to male except for the frons black, white pollinose, black pilose. Anterior anepisternum bare. Female genitalia: 9th tergum with somewhat elliptical black macula concave posteriorly; epiproct as kidney form; cercus slender; hypoproct somewhat triangular; three elliptical spermatecae, one of them smaller.

The current concept of the genus Toxomerus Macquart, 1855 follows Vockeroth (1969). He used mainly male genitalia characters, but noticed the importance of the head shape and abdoinal patterns. The genus Toxomerus has five synonyms: Antiops Enderlein, 1938; Hypobathus Fluke, 1956 (mssp. Hybobathus); Mesogramma Loew, 1866; Mesograpta Loew, 1872; and Mitrosphen Enderlein, 1938. Most of the Toxomerus species were originally described as Mesogramma and Mesograpta.

Toxomerus flaviplurus was described as Mesogramma flaviplura by Hall (1927) and placed in the genus Toxomerus by Thompson et al. (1976). Reemer (2010) synonymized T. flaviplurus and T. costalis based on morphological characters.

Synonyms:

Syrphus costalis Wiedemann, 1830: 140.

Mesogramma flaviplura Hall, 1927: 239.

Mesogramma flavipleura Hull, 1943b: 15, 28.

Mesograpta flaviplura Fluke, 1956: 222.

Toxomerus flaviplurus, Thompson et al. 1976: 50.

Toxomerus costalis (Wiedemann, 1830).

Wiedemann, C.R.W. (1830) Aussereuropaische zweiflugelige Insekten. Zweiter Theil. Schulz, Hamm. xii + 684 pp., 5 pls. [1830.09.22]

GenBank accession number for this species are: protein-coding COI gene (EU409148), rRNA 28S gene (EU409202) and 18S gene (EU409265).

Lenght: body, 7.0-8.0 mm; wing, 6.0-7.0 mm (Borges and Couri 2009).

Toxomerus is the single genus of the tribe Toxomerini. Recently, Mengual et al. (2008) included several species of Toxomerus in their phylogenetic analysis and Toxomerini was resolved as a monophyletic group within the clade of the genus Ocyptamus.

Neotropical species known from Guatemala to Costa Rica, Brazil and Trinidad.