Corethrella (Corethrella) collessi Borkent, 2008

Published, First, 2008, The Frog-Biting Midges of the World (Corethrellidae: Diptera), Zootaxa 1804, pp. 1-456 : 48-50

Corethrella (Corethrella) collessi Borkent , new species

DIAGNOSIS: Male and female adults: only extant species of Corethrella in Australia with unicolorous scales along the anterior margin of the wing (Figs. 61C, 66E), a medium to dark brown scutum ( Fig. 38A), and with darkened non-discrete subapical pigmentation on each femur and tibia ( Fig. 38A).

DESCRIPTION: Male adult. Descriptive statistics: see Tables 2–5. Head: Outline in anterior view somewhat circular (as in Fig. 6D). Two large setae on frons between ventromedial area of ommatida (as in Fig. 16B). Antenna uniformly brown; pedicel without distinctive, more elongate, stout, dorsal or dorsolateral setae; flagellomeres as in Fig. 19C, sensilla coeloconica distributed as in Table 1; flagellomere 13 with welldeveloped apical bifurcation. Palpus brown; segment 3 swollen apically. Thorax (as in Fig. 38A): Medium to dark brown, with scutum, pleura slightly to moderately mottled. 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. Anterior anepisternum divided diagonally by sinuous suture, dorsal portion larger than ventral portion. Ventral portion of posterior anepisternum triangular, uniformly brown, with anterodorsal margin not thick. Wing (Fig. 61C): Apex of R 2 slightly distal to apex of M 1. Distinct band of pigmentation traversing region of r-m; in some, fork of R 2+3, M 1+2, apices of R 2 - M 1 lightly darkened; veins (other than wing margin) with slender scales. Halter paler than scutellum. Legs (as in Fig. 38A): Medium brown with following non-discrete darker pigmentation: forefemur basally (slightly), subapically; foretibia basally, subapically; midfemur basally (slightly), subapically; midtibia basally, subapically; hind femur basally (slightly, missing in some), subapically; hind tibia basally, subapically. 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 tarsomeres 1–3. Apices of fore-, midleg fifth tarsomeres undivided, with claws slightly subapical to apical (as in Fig. 75E). 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 more or less equal in length to fourth tarsomere. Empodia slender. Abdomen (Fig. 76C): Tergites 1–7, sternites 1–7 each with anterior dark brown band; segments 8–9 dark brown (perhaps very posterior margin of segment 8 pale). Genitalia (as in Fig. 83B): Gonocoxite uniformly dark brown, gently tapering; anteromedial area with spicules similar in length to those elsewhere on gonocoxite; with well-defined dorsal row of setae, with setae of increasing thickness anteriorly to posteriorly with 3–4 posteriormost setae equally thick, with row curving posteromedially with posteriormost seta of row positioned dorsomedially. With one dorsomedial stout seta, tapering from base. Gonostylus (in retracted position) straight, thick; of more or less equal thickness for entire length with slight narrowing at midlength, tapered apically; one elongate, thick subbasal seta, situated ventrally; with thick, blunt apical peg. Aedeagus slender, elongate, tapering gradually to apex, pointed apically, with lateral margins separate apically.

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. 16B). Antenna: flagellomeres as in Fig. 25K, sensilla coeloconica distributed as in Table 1. Clypeus ( Fig. 17E) squarish. Mandible with small, pointed teeth. Palpus as in Fig. 33E. Wing (Fig. 66E). Legs: Claws of each leg equal to those of others; equal on each leg, simple (without inner teeth). Abdomen: Tergites and sternites 2–7 each with anterior band of dark pigmentation. Cercus medium brown.

Immatures. Unknown.

DISTRIBUTION AND BIONOMICS: Corethrella collessi is known from eastern Queensland in Australia (Fig. 115B) at altitudes ranging from about 500–950 m, although the exact altitude of several of the collecting sites is uncertain (Colless, pers. comm.). Specimens have been collected with light and Malaise traps.

McKeever and Colless (1991) described the mouthparts of a specimen of the “Cooktown form” from Hitchinbrook Island that was likely a member of C. collessi . However, I did not examine the specimen and its identity is uncertain. Further to this, this site is at sea level and well below the apparent altitude of other collections.

TAXONOMIC DISCUSSION: Males and females were associated through the shared presence of a distinctive pigmentation pattern. In addition, of the specimens examined here, males and females have been collected together at Gap Creek, Moses Creek, Mt. Spec National Park, and Birthday Creek. Most of the specimens studied were in poor condition, appearing bleached and with various parts crushed under coverslips. Fortunately, four males and three females (from Gap, Birthday and Moses Creeks) were received as pinned specimens and made excellent slide preparations. The description of the pigmentation patterns here are based on these latter specimens. Another two males from Moses Creek and 11 males from Gap Creek were left on pins and, although not studied in detail, are considered to be conspecific and are designated as paratypes.

Colless (1986) recognized the taxon at hand as a possible pale variant of C. marksae and called it the “Cooktown form”. Colless (1994) further divided this form into the “Cooktown form” and “Mt Spec form” based on a multivariate analysis (wing and flagellomere measurements). I consider the two forms as conspecific and interpret the differences in measurements as due to size differences between the small samples and the rather poor condition of the slide-mounted material.

Freshly slide-mounted specimens from pinned material indicate that in fact adult C. collessi are equal to C. marksae in thoracic pigmentation but with somewhat lighter wing pigmentation (and with the anterior margin uniformly pigmented) and more extensive (but less intensive) darker pigmentation on the legs. The slidemounted specimens examined by Colless were bleached (as noted by Colless 1994). I therefore consider the “Cooktown form” and “Mt Spec form” to represent a valid but single species. Colless (1986) indicated that there was no difference between the male genitalia of C. marksae and his “Cooktown form” (here C. collessi ) but this is not unusual in the genus and many otherwise distinct species have no discernable differences

between the male genitalia.

TYPES: Holotype, male adult on microscope slide, labeled " HOLOTYPE Corethrella collessi Borkent , 15.505 145.20 E, Gap Ck 5 km ESE Mt. Finnegan, Q., 16 May 1981, D.H. Colless (Malaise Trap), Corethrella sp. “Cooktown form” det D.H. Colless 1985" (ANIC). Allotype, female adult on microscope slide, labeled as for holotype but 14-V-1981 ( ANIC) . Paratypes: 1 ♂, from type locality and date (pinned; ANIC) ; 6 ♂, 3 ♀, from type locality but 15-V-1981 ( ANIC) ; 11 ♂, from type locality but 14-V-1981 (1 slide, 10 pinned; ANIC) ; 6 ♂, 4 ♀, Mt. Spec National Park , 1-IV-1971 ( ANIC) ; 4 ♂, 2 ♀, Birthday Creek , 6 km NW Paluma, Queensland, 25-IX-1980 (2 ♂, 1 ♀ ANIC; 2 ♂, 1 ♀ CNCI) ; 1 ♂, Maidenhair Creek, Mt. Spec National Park , 1- V-1971 ; 2 ♂, 2 ♀, Moses Creek, 4 km N by E Mt. Finnigan (Cooktown), Queensland, 15-X-1980, 16-X-1980 (2 ♂, 1 ♀ ANIC; 1 ♀ CNCI) .

DERIVATION OF SPECIFIC EPITHET: The name collessi is proposed in recognition of the important work on Corethrella and other Diptera by Don H. Colless (ANIC).