Corethrella (Corethrella) towadensis Okada and Hara

Published, First, 2008, The Frog-Biting Midges of the World (Corethrellidae: Diptera), Zootaxa 1804, pp. 1-456 : 127-128

Corethrella (Corethrella) towadensis Okada and Hara

Corethrella towadensis Okada and Hara 1962:49 . Type locality: Hakkoda, Aomori Prefecture, Japan. Holotype ♂ with associated pupal exuviae (type depository stated as Department of Biology and Medical Zoology, Juntendo University, Japan but type apparently lost).

DIAGNOSIS (based on Okada and Hara,1962): Male adult: only extant species of Corethrella in the Palaearctic and Oriental Regions with a wing with a midlength band (as in Fig. 65E), midfemur with the basal half pale and apical half dark brown, and a uniformly dark brown abdomen (as in Fig. 80J). Female adult: unknown.

DESCRIPTION (based on Okada and Hara 1962): Male adult. Descriptive statistics: see Tables 2–5. Head: Outline in anterior view uncertain. Number of large setae on frons between ventromedial area of ommatida uncertain. Antenna light brown (reported as bright yellow); relative flagellomere lengths uncertain. Palpus uncertain. Thorax: Uniformly dark brown but with scutellum light brown. Posterior portion of dorsocentral row uncertain. Prescutal suture uncertain. Form of anterior anepisternum uncertain. Wing: Anterior margin with differently, discretely pigmented scales (indicating anterior margin of midlength band), with midlength band; veins (other than costa and wing margin) with well-developed scales. Halter light brown, as dark as scutellum. Legs: Light brown with following pale: basal half midfemur, apical.6 hind femur, middle 0.4 hind tibia. Presence of scales, spines on midleg tarsomeres 1–3 uncertain. Apices of fore-, midleg fifth tarsomeres uncertain. Each claw without inner tooth. Anterior claws of each leg without a basal prong. Foreleg claws equal (? - stated to be simple). Midleg claws equal. Foreleg third tarsomere length uncertain. Empodia uncertain. Abdomen: Pigmentation of sternite 1–2 uncertain, otherwise uniformly brown. Genitalia (Fig. 92C): Gonocoxite pale at least basally (remainder uncertain), gently tapering; anteromedial area with spicules similar in length to those elsewhere on gonocoxite; with well-defined dorsal row of 8 setae, of similar thickness, with row restricted to dorsal portion of gonocoxite. With one dorsomedial stout seta, tapering near apex. Gonostylus (fully extended) evenly and slightly curved, slender, of more or less equal thickness for entire length, somewhat expanded and rounded apically; two elongate, slender subbasal setae, situated anteroventrally; apical seta slender, short, simple. Aedeagus slender, elongate, tapering gradually from base, rounded apically, with lateral margins fusion uncertain.

Female adult. Unknown.

Pupa. Described by Okada and Hara (1962). Thorax: Scutum, metathorax spherical sensory pits unknown. Respiratory organ: Tubular. Abdomen: Segments 3–7 somewhat expanded laterally. Paddle only moderately elongate; apicodorsal thick spine articulating; apicoventral seta longer than thick spine.

Larva. Described by Okada and Hara (1962).

Egg. Unknown.

DISTRIBUTION AND BIONOMICS: Corethrella towadensis is known only from the type locality on the plateau of Hakkoda , Aomori Prefecture in Japan (Fig. 115A) at an altitude of 740 m. Larvae and pupae were collected on May 21, 1959 from standing water beside a stream which smelled of sulphur. This species is likely more broadly distributed because the nearby activity of the Towada Volcano has almost certainly intensively disturbed the local area. There have been at least six severe Holocene eruptions, the most recent being in 915 AD .

TAXONOMIC DISCUSSION: The type material was stated by Okada and Hara (1962) to be deposited in the Dept. of Biology and Medical Zoology at Juntendo University but is apparently lost ( Miyagi 1980). My further attempts to locate the specimens there and elsewhere in Japan also failed. The type series was composed of a holotype male adult and associated pupal exuviae, 3 pupae each with a larval exuviae, 3 pupae, and 2 larvae.

Okada and Hara (1962) described and illustrated the male with equal and short foreleg claws. If true, they would be the only Corethrella with this condition.

Miyagi (1980) suggested that C. towadensis , known only as males, pupae and larvae may be conspecific with the poorly understood C. japonica , known only from two females and originally described from material collected at Kyoto, Japan. He indicated that there were only some minor differences in the wing venation. However, the thorax and leg pigmentation patterns also differ, suggesting they are distinct.

The types of C. japonica are also missing and there is a need to recollect Corethrella from Japan to sort out these possibilities.

MATERIAL EXAMINED: No specimens studied.

DERIVATION OF SPECIFIC EPITHET: The name towadensis refers to Towada, Japan, a town and volcano near the type locality .