Toxomerus geminatus (Say, 1823):92

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 geminatus is a small species (less than 9 mm in lenght), scutum with lateral yellow vitta continuos from postpronotum to scutellum; scutellum yellow pilose; anepimeron black; and abdomen with pale medial areas with submedial black vittate maculae.

New description:

MALE.

Head: Face produced forward ventrally, with facial tubercle, yellow, yellow pilose; gena yellow anteriorly, black posteriorly, yellow pilose; frontal triangle yellow, yellow pilose; vertical triangle elongate, black, bronze pollinose, black pilose; antenna yellow, arista brown; eye bare, holoptic, eye contiguity as long as the length of basoflagellomere and pedicel together; occiput black, silvery-golden pollinose, withish-yellow pilose.

Thorax: Scutum black with yellow vita on lateral margin from postpronotum to scutellum, bronze pollinose with dorsomedial bluish-white pollinose vitta, yellow pilose; postpronotum yellow, bare; scutellum mostly black with yellow lateral and posterior margins, yellow pilose with 1-3 black pili posteriorly, subscutellar fringe sparse with yellow pile. Pleuron mostly black, except posterior anepisternum yellow on posterior half, metaepisternum yellow, and katepisternum black with dorsal yellow macula; metasternum bare; calypter yellow; plumula yellow; halter yellow; spiracular fringes yellow. Wing: Wing membrane hyaline, stigma brownish; mostly microtrichose, bare basally on 2nd costal cell and cells R1, R, BM and CuP. Alula as broad as cell BM medially, microtrichose. Legs: Pro- and mesolegs yellow except procoxa black, and pro- and mesotarsi dark yellow, mostly yellow pilose except mesofemur with black setae-like pile apically. Metacoxa and metatrochanter yellow, yellow pilose; metafemur extremely arcuate, yellow on basal 1/3 and black on apical 2/3, black pilose posterolaterally; metatibia modified, arcuate and expanded apically, black with yellow areas basally, medially and apically, metatarsus dark brown, black pilose anterolaterally and golden pilose posterolaterally.

Abdomen: Parallel-sided; yellow pilose dorsally and laterally except black pilose on posterior 1/3 of lateral margin of terga 2nd, 3rd, 4th and 5th, and black pilose dorsally on black areas; 1st tergum black except yellow laterally and on anterolateral corners; 2nd tergum black with medial broad yellow fascia, sometimes medially interrupted by narrow black vita; 3rd and 4th terga yellow with black fascia on posterior margin (medially interrupted or not), extended towards anterior margin forming sublateral black vittae that do not reach anterior margin on 3rd tergum, but reach anterior margin on 4th tergum, with 2 submedial vittate maculae forming a medial yellow vita, which usually does not reach anterior margin on 4th tergum; 5th tergum yellow with 3 diamond-shaped black vittae that can be connected medially; sterna yellow, yellow pilose; genitalia enlarged.

FEMALE.

Differs from the male as follows: frons black with lateral narrow yellow vittae not reaching ocellar triangle, black pilose medially, yellow pilose on lateral yellow areas; metafemur slightly arcuate, yellow with subapical black ring, metatibia simple, not strongly arcuate or expanded apically.

Synonyms:

Scaeva geminatus Say, 1823: 92.

Toxomerus notatus Macquart, 1855: 113.

Eumerus privernus Walker, 1852: 225.

Syrphus interrogans Walker, 1852: 238.

Toxomerus geminatus (Say, 1823).

Say, T. (1823) Descriptions of dipterous insects of the United States. Journal of the Academy of Natural Sciences of Philadelphia 3, 9-32 [1823.04.??], 33-64 [1823.05.??], 73-104.

GenBank accession number for this species are: protein-coding COI gene (EU409158), rRNA 28S gene (EU409212),18S gene (EU409275), ABC membrane transporter (white) gene (AY055823), 16S gene (AF154819), and 12S gene (AF154744; AF154743).

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.

Nearctic species known from Minnestoa to Quebec, south to Texas and Florida.

Puparium (from Heiss 1938).

Length, 7 mm; width, 2 mm; height, 2 mm; broad and evenly rounded at anterior end and tapering evenly toward the rear. The color is light golden-brown. Two dark lines are present along the sides in the same position as those in marginata and of about the same extent. The posterior spiracular plates are contiguous in the puparium, and from their structure were evidently so in the larva as well. The spiracles, as in the other puparia of Toxomerus, are raised on blackened carinae.