Corethrella (Corethrella) rotunda Borkent, 2008

Published, First, 2008, The Frog-Biting Midges of the World (Corethrellidae: Diptera), Zootaxa 1804, pp. 1-456 : 60-61

Corethrella (Corethrella) rotunda Borkent , new species

DIAGNOSIS: Male adult: only extant species of Corethrella in the New World with flagellomeres 1 and 2 both short ( Fig. 19I), a plain wing and with R 2 elongate (longer than the stem of R 2+3) (Fig. 61H), and uniformly pigmented thorax and legs (slightly lightened at knees) ( Fig. 40B). Female adult: only extant species of Corethrella in the New World with a circular head (in anterior view) ( Fig. 6I), with flagellomere 1 moderately elongate ( Fig. 26G), with uniformly pigmented wing (Fig. 67B), scutum, katepisternum ( Fig. 40B), and legs (with only apical 0.2 of hind femur somewhat lighter) ( Fig. 40B), wing with slender scales (as in Fig. 73B), and apex of R 2 terminating equal to apex of M 1 (Fig. 67B).

DESCRIPTION: Male adult. Descriptive statistics: see Tables 2–5. Head: Outline in anterior view nearly circular (as in Fig. 6I). Two large setae on frons between ventromedial area of ommatida (as in Fig. 16F). Antenna uniformly brown; pedicel with slightly developed more elongate, stout, dorsal or dorsolateral setae; flagellomeres as in Fig. 19I, sensilla coeloconica distributed as in Table 1; flagellomere 13 with welldeveloped apical bifurcation; flagellomeres 5–7 each with ventral, elongate, stout seta. Palpus brown; segment 3 swollen apically. Thorax (as in Fig. 40B): nearly uniformly brown, pale sclerites around base of wing. Posterior portion of dorsocentral row with single elongate setae situated somewhat lateral to one another. Prescutal suture elongate, interrupted by area of pale cuticle. Anterior anepisternum divided diagonally by sinuous suture, dorsal portion about equal to ventral portion. Ventral portion of posterior anepisternum not differentiated from dorsal portion, anterior margin more darkly pigmented than posterior margin. Wing (Fig. 61H): Apex of R 2 equal to apex of M 1. Plain, without pattern of pigmented veins and/or scales; veins (other than costa and wing margin) with very slender scales. Halter somewhat lighter than scutellum. Legs (as in Fig. 40B): Uniformly pigmented, with knees slightly lighter. With only slender setae, lacking scales (except for some in patch of whip-like setae on posterior portion of hind tibia). Midleg with thick, sub- apical setae on each of at least tarsomeres 1–3. Apices of fore-, midleg fifth tarsomeres undivided, with claws slightly subapical to apical (as in Fig. 75F). Claw of foreleg longer than those of mid-, hind leg. Each claw without inner tooth. Anterior claws of each leg without a basal prong. Foreleg claws unequal. Midleg claws equal. Foreleg third tarsomere somewhat longer than fourth tarsomere. Empodia slender. Abdomen (Fig. 76H): Uniformly brown. Genitalia (Fig. 84D): Gonocoxite uniformly medium brown, gently tapering; anteromedial area with spicules similar in length to those elsewhere on gonocoxite; with well-defined dorsal row of setae, with setae stouter than other scattered setae on gonocoxite, of nearly equal thickness but with posteriormost seta slightly more slender, with row curving posteromedially with posteriormost seta of row positioned somewhat dorsomedially. With one dorsomedial stout seta, tapering from base. Gonostylus (in retracted position) curved subapically, moderately slender, of more or less equal thickness for entire length, rounded apically; one elongate, thick subbasal seta, situated posteroventrally; with well-developed apical peg. Aedeagus slender, elongate, tapering from base but with abrupt narrowing subapically, pointed apically, with lateral margins fused at apex.

Female adult. Descriptive statistics: see Tables 6–11. As for male, with following differences. Head: Coronal suture short, extending ventrally about midway along area between ommatidia (as in Fig. 16F). Antennal flagellomeres as in Fig. 26G, sensilla coeloconica distributed as in Table 1. Clypeus ( Fig. 17K) squarish. Mandible with small, pointed teeth. Palpus as in Fig. 33M. Wing (Fig. 67B). Halter as dark as or somewhat lighter than scutellum. Legs ( Fig. 40B): Uniformly pigmented or with knees somewhat lighter or with apical 0.25 of hind femur somewhat lighter or with basal 0.3 of hind femur somewhat lighter. Claws of each leg equal to those of others; equal on each leg, simple (without inner teeth). Abdomen: Uniformly dark brown. Cercus dark brown.

Immatures. Unknown.

DISTRIBUTION AND BIONOMICS: Corethrella rotunda is known only from Costa Rica (Fig. 121A) at an altitude of 0– 600 m. Specimens have been collected using frog-call and Malaise traps. The specimen from Atenas was collected by sweeping near and over a small spring that created a small wet area; this spring was about 100 meters from a moderately sized river. The serrate mandibles of the female adults and the attraction of two females (from 5 km NE Tárcoles) to Hyla gratiosa calls suggest that they feed on frog blood in nature. However, the frog-call trap was run for many hours in this locality, collecting numerous other Corethrella but only one female C. rotunda , suggesting either that it is rare, that the call of H. gratiosa is not particularly attractive to females of this species, or that its primary emergence period is between March and July, when the trap was not run in this location.

TAXONOMIC DISCUSSION: Male and females were associated through the presence of shared pigmentation and were collected together in Tortuguero National Park. There was more variation in the leg pigmentation in females of this species than is otherwise present in most species of Corethrella , suggesting the possibility that some of these are not conspecific.

TYPES: Holotype, male adult on microscope slide, labeled " HOLOTYPE Corethrella rotunda Borkent ”, “ COSTA RICA, Prov. Limón, P.N. Tortuguero. Send. Real a Agua Fria. 98 m. 14–21 AGO 2004. Porras, Gamboa, Briceño, Moraga, Cardenas. Malaise LN261724 588486, #77942" (INBC). Allotype, female adult on microscope slide, labeled as for holotype ( INBC) . Paratypes: 3 ♂, 4 ♀, labeled as for holotype (2 ♂, 2 ♀, INBC; 1 ♂, 2 ♀, CNCI) ; 1 ♀, labeled as for holotype but 20–50 m ( USNM) ; 2 ♀, 5 km NE Tárcoles, Costa Rica , 20-VII-1993 ( CNCI) ; 1 ♀, Laguna Gandoca, Prov. Limón, Costa Rica , 0–50 m, 17-23-V-2004 ( INBC) ; 1 ♂, 5 ♀, Bosque Nacional Dirai, Santa Cruz , Guanacaste, Costa Rica, 120–140 m (1 ♂, 3 ♀, INBC; 2 ♀, CNCI) ; 1♀, Atenas, Costa Rica , 29-XI-1993 ( CNCI) ; 1 ♀ Estación Los Patos, Corcovado National Park, Costa Rica , 25-XII-2000 – 13-II-2001 ( INBC) .

DERIVATION OF SPECIFIC EPITHET: The name rotunda refers to the round head capsule present in the adults of this species (also present in some other species).