Corethrella (Corethrella) baltica Borkent, 2008

Published, First, 2008, The Frog-Biting Midges of the World (Corethrellidae: Diptera), Zootaxa 1804, pp. 1-456 : 200-201

Corethrella (Corethrella) baltica Borkent , new species

DIAGNOSIS: Male adult: only species of Corethrella with an aedeagus extending to near apex of gonocoxite (Figs. 99D, E). Female adult: unknown.

DESCRIPTION: Male adult. Habitus as in Fig. 112D. 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: pedicel without more elongate, stout, dorsal or dorsolateral setae; flagellomeres as in Fig. 25C; sensilla coeloconica not visible; shape of flagellomere 13 apex uncertain. Clypeus uncertain. Palpus ( Fig. 35 AD) with segment 3 swollen apically. Thorax: Posterior portion of dorsocentral row with 2 elongate setae situated somewhat lateral to one another. Prescutal suture elongate, thick, uninterrupted, extending to near dorsocentral row of setae. Details of shapes of pleura uncertain. Wing (similar to that of C. miocaenica , Fig. 2 in Szadziewski et al. 1994): Apex of R 2 equal to apex of M 1. Veins (other than costa and wing margin) with very slender scales. Legs: With only slender setae, lacking scales (except for some in patch of whip-like setae on posterior portion of hind tibia). Midleg without thick, subapical setae on each of at least tarsomeres 1–3. Apices of fore-, midleg fifth tarsomeres undivided, with claws slightly subapical to apical (Fig. 75C). Claws of fore-, midleg longer than those of hind leg. Each claw without inner tooth. Anterior claws of fore-, midleg with basal prong. Both claws of given leg equal length. Foreleg third tarsomere longer than fourth tarsomere. Empodia absent. Genitalia (Figs. 99D–G): Somewhat distorted. Gonocoxite gently tapering; anteromedial area with spicules similar in length to those elsewhere on gonocoxite; with dorsal row of setae of 5–6 setae, with terminal 3 setae thickest, with row curving posteromedially with posteriormost seta of row positioned dorsomedially. Without dorsomedial seta. Gonostylus (in retracted position) straight, thick; expanding distally to truncate apex; subbasal seta moderately thick, situated ventrally; apical seta or peg not visible. Aedeagus slender, elongate, extending to near apex of gonocoxite.

Female adult and immatures. Unknown.

DISTRIBUTION AND BIONOMICS: Corethrella baltica is known only from Baltic amber (Fig. 139), dated at 44.1 Mya. The specimen was originally in a piece of amber including a mite and a Mycetophilidae which were removed upon preparation ( Sontag 2001).

TAXONOMIC DISCUSSION: Sontag (2001) identified the holotype of C. baltica as a specimen of C. miocaenica , a species previously known from Saxonian amber. However, the distinctive, elongate aedeagus clearly distinguishes it from all other species of Corethrella , including C. miocaenica . In addition, there seems to be a significant difference in the ratio of Ta3/Ta4 between C. baltica and C. miocaenica , as suggested in the cladistic analysis of these species.

The holotype is mostly cleared and portions are distorted. The thorax is divided medially into separate portions, the right midleg tarsomeres are missing, and the abdomen is mostly distorted, including one gonocoxite. Sontag (2001) gave the specimen number as 3631 but it is actually 3613 (as noted in a handwritten correction on a received reprint and on the slide bearing the amber piece).

Although C. baltica lacks many features of the subgenus Corethrella , it is placed here because it has derived character states 14 and 17 (male claws lacking teeth, gonocoxite with dorsal row of setae).

TYPES: Holotype, male adult in amber on microscope slide, labeled " HOLOTYPE Corethrella baltica Borkent ”, “3613, MTM37, Muzeum Inkluzji w Bursztynie, Katedra Zoologii Bezkr Š gowców, Uniwersytet Gda Ł ski, Diptera : Mycetophilidae , Diptera : Corethrellidae ♂, Arachnida: Acarina, Tomasz Debowski & Maciej Szulimowicz, 09.09.2000 ” ( MAIG).

DERIVATION OF SPECIFIC EPITHET: The name baltica refers to area from which this amber specimen originates.