Corethrella (Corethrella) ramentum Borkent, 2008

Published, First, 2008, The Frog-Biting Midges of the World (Corethrellidae: Diptera), Zootaxa 1804, pp. 1-456 : 75-77

Corethrella (Corethrella) ramentum Borkent , new species

DIAGNOSIS: Male and female adults: only extant species of Corethrella in the New World with the palpus entirely brown ( Fig. 7H), a completely plain wing (Figs. 62B, 67L), entire thorax dark brown ( Fig. 43A), halter as dark as scutellum, midfemur with darker pigmentation at its base, hind tibia uniformly light brown ( Fig. 43A).

DESCRIPTION: Male adult. Descriptive statistics: see Tables 2–5. Head: Outline in anterior view (as in Fig. 7H). Four large setae on frons between ventromedial area of ommatida (as in Fig. 16D). Antenna uniformly brown; pedicel with at least one distinctive, more elongate, stout, dorsal or dorsolateral seta; flagellomeres as in Fig. 20E, sensilla coeloconica distributed as in Table 1; flagellomere 13 with well-developed apical bifurcation. Palpus brown; segment 3 of constant width. Thorax (as in Fig. 43A): uniformly dark brown. Posterior portion of dorsocentral row with 2 elongate setae situated somewhat lateral to one another. Prescutal suture short, not extending more than half way to dorsocentral row of setae. Anterior anepisternum divided diagonally by sinuous suture, dorsal portion about equal to ventral portion. Ventral portion of posterior anepisternum triangular, uniformly brown, with anterodorsal margin thick. Wing (Fig. 62B): 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 well-developed scales. Halter as dark as scutellum. Legs (as in Fig. 43A): Light to medium brown with following more darkly pigmented: in holotype forefemur, fore tibia (light in paratype), basal 1/4 of midfemur. Femora, tibiae and at least some tarsomeres with broad scales (also some in patch of whip-like setae on posterior portion of hind tibia). Midleg with thick, subapical setae on each of at least tarsomeres 1–3. Apices of fore-, midleg fifth tarsomeres bilobed in dorsoventral view, with claws subapical (as in Fig. 75E). Elongate claw of foreleg shorter than that of midleg, both longer than those of hind leg. Each claw without inner tooth. Anterior claws of each leg without a basal prong. Foreleg claws unequal. Midleg claws unequal. Foreleg third tarsomere longer than fourth tarsomere. Empodia slender. Abdomen (Fig. 77C): Uniformly light to medium brown. Genitalia (Fig. 86D): Gonocoxite uniformly pale or medium brown, somewhat tapering; anteromedial area with distinctively elongate spicules; with well-defined dorsal row of setae, with 2–3 basal setae of row stout, enlarged and bent subapically, 2 more posterior setae slender, with row restricted to dorsal portion of gonocoxite. With two dorsomedial stout setae, tapering from base, anterior seta more stout, bases joined by sclerotized plate. Gonostylus (in retracted position) straight, basal 0.6 thick, narrowed beyond to rounded apex; one elongate, thick subbasal seta, situated posteroventrally; apical seta slender, elongate, simple. Aedeagus squat, somewhat triangular, tapering gradually to apex, somewhat 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 elongate, extending ventrally past ommatida (as in Fig. 16D). Antenna brown with basal half of flagellomere 1 more darkly pigmented in Costa Rican specimens; with flagellomeres as in Fig. 27D, sensilla coeloconica distributed as in Table 1. Clypeus ( Fig. 17U) squarish. Mandible with large, apically somewhat squared teeth. Palpus as in Fig. 33W. Wing (Fig. 67L). Legs ( Fig. 43A): Pigmentation as for males but specimen from 5 km NE Tárcoles, Costa Rica darker pigmentation at very base of fore-, hind femora. Apices of fore-, midleg fifth tarsomeres undivided, with claws situated slightly subapically to apically. Claws of each leg equal to those of others; equal on each leg, simple (without inner teeth). Abdomen: Uniformly medium to dark brown.

Pupa. Unknown (but see below).

Larva. Unknown (but see below).

Egg. Unknown.

DISTRIBUTION AND BIONOMICS: Corethrella ramentum is known from Costa Rica and Trinidad and Tobago (Fig. 136) at altitudes ranging from 0– 300 m. Specimens have been collected using frog-call and light traps. The serrate mandibles of the female adults and their attraction to Hyla gratiosa calls suggest that they feed on frog blood in nature. Immature stages have been reared from animal tracks, a blocked stream and a stream margin. The specimens from the Belkin “Mosquitoes of Middle America” project are identified in Table 12.

TAXONOMIC DISCUSSION: Males and females were associated through the shared presence of a common pigmentation pattern and were collected together at one location in Tobago. The specimens at hand exhibited significant variation in degree of pigmentation (of foreleg, female flagellomere 1, from medium to dark brown thorax) as well as relative lengths of the female flagellomeres 1–3 (those from Trinidad and Tobago with shorter flagellomere 1), suggesting that perhaps more than one species is included under this name. More material is needed to interpret this variation.

Two females from Sendero Toma de Agua, Valle de la Estrella, Hitoy Cere Biological Reserve, Costa Rica, 100–140 m, 17-XI–17-XII-1999 (INBC) key to this species but have very short flagellomeres 1–3 and elongate flagellomeres 4–13 (somewhat similar to that of C. pallida but with flagellomere 4 more elongate). They clearly represent an undescribed species but were studied too late to include in the current revision.

One female from Bosque Mesofilo de Montaña, 4 km on highway Tlanchinol-Apantlazol, Hidalgo Tianchinol, Mexico, 7-V-1997, 1475 m and four females from the same locality but collected 8-III-1997 at 1470 m (IDRE) keyed to C. ramentum except that they were significantly lighter in pigmentation. They likely represent an undescribed species but may yet be variable members of C. ramentum . I have identified them as “ Corethrella nr. ramentum ”.

Some specimens from Trinidad and Tobago were reared during the Belkin “Mosquitoes of Middle America” project but I have not examined the immature stages of this species (likely in the USNM).

TYPES: Holotype, male adult on microscope slide, labeled " HOLOTYPE Corethrella ramentum Borkent , Costa Rica. Prov. Puntarenas, Golfito, Estación Agujas, 300 m. 09–25 ENE 2001. J. Azofeifa. Amarilla. LS 526550 276750. #61207" (INBC). Allotype, female adult on microscope slide, Punta Marenco , Puntarenas, Costa Rica, 0 m, 12-III-2001 ( CNCI) . Paratypes: 1 ♀, 5 km NE Tárcoles , Costa Rica, 20 m, 2-IX- 1993 ( CNCI) ; 1 ♂, 5 ♀, St. George , about 3km E of Mason Hall, Easterfield, Trinidad and Tobago, 220 m, 26- XI-1965 ( USNM) ; 1 ♀, St. George , about 4km E of Mason Hall, Caledonia, Trinidad and Tobago, 270 m, 26- XI-1965 ( USNM) ; 4 ♀, St. George , about 3 km E of Mason Hall, Easterfield at 2 3/4 milepost, Trinidad and Tobago, 220 m, 29–30-XI-1965 ( USNM) ; 1 ♀, Nariva , “Archers Estate “, 50 m, Trinidad and Tobago, 5-XI- 1964 ( USNM) .

DERIVATION OF SPECIFIC EPITHET: The name ramentum (loose scales) refers to the presence of scales on the femora and tibia of this species (also present in some other species). The name is treated as a noun in apposition.