Corethrella (Corethrella) aridicola Borkent, 2008

Published, First, 2008, The Frog-Biting Midges of the World (Corethrellidae: Diptera), Zootaxa 1804, pp. 1-456 : 169-171

Corethrella (Corethrella) aridicola Borkent , new species

Corethrella laneana: Belkin and McDonald 1955:82 . Cook 1956:62. Stone 1968:185. McKeever 1986. McKeever and French 1991b.

DIAGNOSIS: Male adult: only extant species of Corethrella in the New World with clypeus elongate (as in Fig. 18 AD), a distinct midlength wing band (Fig. 65A), wing veins with slender scales (as in Fig. 73B), thorax medium brown ( Fig. 56A), halter pale and lighter than scutellum, midfemur medium brown and equal to that of base of hind femur, base of hind tibia more darkly pigmented (contrasting with pale apex of hind femur), mid- and hind leg tarsomeres 2-4 uniformly pigmented (no bands on any tarsomeres) ( Fig. 56A), midfemur without scales, abdominal segments 7 and 8 equally medium brown, segment 9 and base of gonocoxite equally dark brown (Fig. 80H). Female adult: only extant species of Corethrella in the New World with the clypeus elongate ( Fig. 18 AD), flagellomeres 2 and 3 elongate ( Fig. 31G), a distinct midlength wing band but with dark scales absent on CuA 2 (Fig. 71G), thorax medium brown ( Fig. 56A), midfemur medium brown and equal to that of base of hind femur, base of hind tibia more darkly pigmented (contrasting with pale apex of hind femur) ( Fig. 56A), and midfemur without scales.

DESCRIPTION: Male adult. Descriptive statistics: see Tables 2–5. Head: Outline in anterior view laterally elongate (as in Fig. 13E). Two large setae on frons between ventromedial area of ommatida (as in Fig. 16F). Antenna medium brown; pedicel with at least one distinctive, more elongate, stout, dorsal or dorsolateral seta; flagellomeres as in Fig. 24D, sensilla coeloconica distributed as in Table 1; flagellomere 13 with well-developed apical bifurcation. Palpus light brown; segment 3 of nearly constant width. Thorax (as in Fig. 56A): Light to medium brown, pale sclerites around base of wing. Posterior portion of dorsocentral row with group of about 5 elongate setae. 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. 65A): Apex of R 2 basal to apex of M 1. Anterior margin with differently, discretely pigmented scales (indicating anterior margins of wing bands), with distinct midlength band but with dark scales absent on CuA 2, subbasal band with dark scales on C, Sc, R, M, dark scales on R 2 apex extending to wing margin; veins (other than costa and wing margin) with slender scales. Halter pale or very light brown. Legs (as in Fig. 56A): Medium brown, with fore-, midleg knees pale, fore-, midtibiae darker at apices, hind femur with apical 0.3–0.4 pale, hind tibia pale with basal and apical non-discrete darker brown pigmentation. With only slender setae, lacking scales (except for 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 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 shorter than fourth tarsomere. Empodia slender. Abdomen (Fig. 80H): Medium brown. Genitalia (Fig. 96D): Gonocoxite medium brown, slightly lighter apically, gently tapering; anteromedial area with spicules similar in length to those elsewhere on gonocoxite; with well-defined dorsal row of setae, with setae 2, 3, 4 thicker than others; with row restricted to dorsal portion of gonocoxite. With one dorsomedial stout seta, tapering from base. Gonostylus (partially extended) nearly straight, gently curved near apex, slender, of more or less equal thickness for entire length but somewhat thicker apically, pointed apically; one elongate, slender, subbasal seta, situated anteriorly or anteroventrally; apical seta slender, elongate, simple. Aedeagus slender, elongate, tapering gradually to apex, with slender apex, pointed apically, with lateral margins fused subapically or near 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). Antenna; with flagellomeres as in Fig. 31G, sensilla coeloconica distributed as in Table 1. Clypeus ( Fig. 18 AD) elongate. Mandible with small, pointed teeth. Palpus as in Fig. 35J. Wing (Fig. 71G). Legs: Claws of each leg equal to those of others; equal on each leg, simple (without inner teeth). Abdomen: Medium brown with segments 8–9 darker brown. Cercus medium brown.

Pupa. Described by Belkin and McDonald (1955), Cook (1956), McKeever and French (1991b). Thorax: Scutum, metathorax each with spherical sensory pit (as in Fig. 100A). Respiratory organ (Fig. 103G): Tubular. Abdomen (Fig. 110D): Segments 3-7 somewhat expanded laterally. Paddle only moderately elongate; apicodorsal thick spine articulating; apicoventral seta longer than thick spine.

Larva. Described by Belkin and McDonald (1955), Cook (1956), McKeever and French (1991b).

Egg. Unknown.

DISTRIBUTION AND BIONOMICS: Corethrella aridicola is known only from two localities, one at Saratoga Springs, Death Valley in southern California, USA and the other from Guadalupe Hot Springs in Baja California, Mexico (Fig. 117A) at altitudes of 70- 300 m. It appears that this species has a restricted distribution. McKeever and French (1991b) searched in vain for the species at Tecopa Hot Springs, only 25 km from Saratoga Springs where females were abundant. Lund (2000) recorded this species (as C. laneana ) from Peña Spring, Big Bend National Park, Texas, USA, but I was unable to study original material and cannot confirm the identification.

Adult specimens have been collected by rearing, and with light and frog-call traps. The serrate mandibles of the female adults ( McKeever 1986) and their attraction to Hyla gratiosa and H. avivoca Viosca calls ( McKeever and French 1991b) suggest that they feed on frog blood in nature. The only anurans in Death Valley are the Red spotted toad ( Bufo punctatus Baird and Girard ), Western toad ( Bufo boreas Baird and Girard ), Pacific treefrog ( Pseudacris regilla (Baird and Girard)) and the recently introduced Bullfrog ( Rana catesbeiana Shaw ) and one or more of these are hypothesized as the host of C. aridicola . Belkin and McDonald (1955) reported the larva, like those of most other Corethrella , to be sluggish and rarely coming to the surface. They could not make any observations of feeding on proffered small Crustacea or young instars of mosquito larvae and found them difficult to rear. The pupa floated in a horizontal position below the surface and emerged after 4-5 days. Larvae and pupae were present in “almost total darkness in mats of Scirpus olneyi on the margin of a large spring-fed pond”. The single male from Baja California was reared from a larva collected from a spring in a desert canyon where the permanent water was brownish and choked with sedges and in deep shade.

Belkin and McDonald (1955) found larvae at Saratoga Springs to be common in July, scarce in September and absent in October. Adults are abundant there at least in October, with 609 females collected in 90 minutes with four frog-call traps ( McKeever and French 1991b) but were not attracted to a trap in late May (McKeever, pers. comm.).

TAXONOMIC DISCUSSION: Males and females were associated through the shared presence of a common morphology and have been collected together at the type locality. Previous references to C. laneana in the United States by Belkin and McDonald (1955), Cook (1956), Stone (1968); McKeever (1986), McKeever and French (1991b) and Stone (1968) refer to C. aridicola . Belkin and McDonald (1955) noted some differences in wing pigmentation between their material from Saratoga Springs and that of C. laneana (here = C. puella ) and considered the possibility of naming it as a subspecies. The lighter body pigmentation, less extensive wing pigmentation, fewer anepimeral setae, and more slender wing scales of adult C. aridicola supports their recognition as distinct species.

The sensilla coeloconica of C. aridicola are unusually small and is perhaps related to their unusual desert habitat. McKeever (1986) described the female mouthparts of C. aridicola (as C. laneana ). Cook (1956) described the gonostylus of this species (as C. laneana ) with two subbasal setae on the gonostylus but none of the specimens I examined exhibited this condition.

TYPES: Holotype, male adult on microscope slide, labeled " HOLOTYPE Corethrella aridicola Borkent ”, “ ♂ Corethrella laneana Vargas subsp., Det. ‘54 J.N. Belkin”, “Saratoga Sprs. Death Valley, Cal. VII-28-54, Belkin & McDonald ”, “Lot 127 Sub 104” (USNM). Allotype, female adult on microscope slide, pupal exuviae on separate slide, labeled as for holotype but “IX-10-11-54" and “Lot 143 Sub 201" ( USNM) . Paratypes: 1 ♂, 1 ♀, each with larval and pupal exuviae, 1 ♂ (pinned with genitalia on slide), 3 ♀, 1 pupa, 10 larvae, 2 larval and pupal associated exuviae, labeled as for holotype ( USNM) ; 1 ♂, 1 ♀, each with larval and pupal exuviae, 1 ♀ (pinned), 5 larvae, labeled as for allotype ( USNM) ; 1 ♀, from type locality but 20-III-1955 ( USNM) ; 8 ♀ (slides), 22 ♀ (pinned), Saratoga Springs , Death Valley, California, USA, 23-24-X-1986 ( CNCI) ; 1 ♂ with larval and pupal exuviae, Guadalupe Hot Springs , about 60 km SW Mexicali, Baja California, Mexico, 300 m, 26-X-1967 ( USNM) .

DERIVATION OF SPECIFIC EPITHET: The name aridicola (dry, inhabiting) refers to the habitat of this species.