Corethrella (Corethrella) alticola Lane, 1939

Amaral, André P., Mariano, Rodolfo & Pinho, Luiz Carlos, 2023, Description of five new species of frog-biting midges (Diptera, Corethrellidae) from Brazil and examination of new morphological characters with utility for taxonomic and phylogenetic studies, European Journal of Taxonomy 874 (1), pp. 1-120 : 33-37

Corethrella (Corethrella) alticola Lane, 1939

Fig. 15 ; Appendix 1

Corethrella alticola – Amaral & Pinho 2015: 282 , figs 25–28.

Diagnosis

Larva

Only extant species with the following combination of characters: darkly pigmented tergal plates; a darkly colored mandibular lobe ( Amaral & Pinho 2015: fig. 26); head uniformly light/medium brown ( Amaral & Pinho 2015: fig. 26); mandible with a discretely long apical tooth (2.0–2.67 times length of first dorsal tooth) ( Fig. 15F ); subgenal carina covered with minute spinules ( Fig. 15F ).

Pupa

Only extant species with the following combination of characters: a flattened, wide, trilobed respiratory organ ( Amaral & Pinho 2015: fig. 23); exuvia lightly pigmented, yellowish ( Amaral & Pinho 2015: fig. 22); abdominal segments III–VII strongly expanded lateroposteriorly, more darkly pigmented laterally ( Amaral & Pinho 2015: fig. 22); abdominal setae on segments I–VIII weakly developed (this species may be difficult to distinguish from C. manaosensis ; see Remarks).

Material examined

BRAZIL – Santa Catarina State • 1 ♀, adult, with larval and pupal exuviae; Grão Pará, Parque Estadual Serra Furada , CAPEA Stream ; 28°11ʹ26ʺ S, 49°23ʹ30ʺ W; 7 Apr. 2013; L.C. Pinho, A.L. Schlindwein and A.P. Amaral leg.; hand net; CE-MHS • 1 ♀, adult, with larval and pupal exuviae; same collection data as for preceding, except 7 May 2013; L.C. Pinho and V. Freitas leg.; CE-MHS • 1 ♂, adult, with larval and pupal exuviae; Orleans, Rio Minador ; 28°10ʹ43ʺ S, 49°24ʹ33ʺ W; 8 Jun. 2013; LC Pinho et al. leg.; hand net; CE-MHS . – Bahia State • 1 ♂, 1 ♀, adults, with respective pupal and larval exuviae; Rio de Contas, Parque Natural Serra das Almas , Vale do Queiroz , “mata de galeria” [riparian woodland]; 13°31ʹ28ʺ S, 41°57ʹ24ʺ W; 1579 m a.s.l.; 30 Nov. 2019, A.P. Amaral leg.; hand net; CE-MHS .

Description

Male and female adults (2 ♂♂, 3 ♀♀)

HEAD. Compound eyes (of specimens in ethanol) iridescent green. Female antenna ( Fig. 15A–B ) medium brown, with basal half of flagellomeres I–VII pale. Flagellomere I moderately to very elongate, II–III elongate, XIII apically bifurcated. Sensilla coeloconica distribution: 1(II–VIII), 2([VII, VIII], IX– XIII), 4(I). Sensilla ( Fig. 15C ): Ocular row with 2 thick offset setae on ventral part, more dorsally 10–12 setae, extending shortly beyond vertex. Subocular row poorly defined anteriorly, with about 12 setae on posterior portion. Interocular space and vertex densely setose. Postgenal row with 18–60+ slender setae, ranging from posterior part of ocular row to ventromedially. With 1 thick ventromedial seta.

THORAX. Sensilla ( Fig. 15D ): Antepronotum with 3–4 slender anterodorsal setae. Postpronotum with 1 thick dorsal and 1–3 slender setae. Scutum, prescutal area with 2–6 anterior thick/intermediate and 2 posterodorsal thick setae; about 15–28 slender setae surrounding. Antealar area with cluster of 9–11 thick/intermediate and 4–9 slender setae on posteroventral portion. Supraalar area with 2–3 thick, 2–5 intermediate, and 5–13 slender setae.Dorsocentral row, posterior part with 4–6 thick offset, longitudinally aligned setae; approximately 27–37 thick/intermediate and about 26–50 slender setae filling row. Row interrupted at level of prescutal suture. Scutellum with 8–10 thick setae. Posterior anepisternum with 1–4 dorsal setae.Anepimeron bare.

WING. Male R 3 /R 1: 0.45–0.48; R 2+3 /R 2: 0.57–0.60. Female R 3 /R 1: 0.63 (0.61–0.65); R 2+3 /R 2: 0.36 (0.34– 0.39).

LEGS. Empodium ( Fig. 15E ) short, slender, with two branches. Male Ta1/Ta2: 2.21–2.29; Ta3/Ta4: 1.50– 1.60. Female Ta1/Ta2: 2.35 (2.28–2.42); Ta3/Ta4: 1.43 (1.42–1.46).

Larva (n = 4)

EXUVIA ( Amaral & Pinho 2015: 282, fig. 26). Uniformly light to medium brown with more darkly pigmented tergal plates on I–VII.

HEAD ( Fig. 15F ). Roughly triangular shaped in dorsoventral view, 1.11 (1.10–1.14) times as wide as long. Antenna 0.57 (0.55–0.60) times length of head; antennal groove 1.36 (1.25–1.45) times length of antenna; ventral margin of antennal groove with about 6 moderately developed denticles. Postmentum with wide base, strongly tapering distally, 1.58 (1.50–1.67) times as wide as long; length about 0.35 (0.34–0.36) of head. Prementum almost straight, with 13–17 triangular teeth, darkly pigmented, central one largest, remaining gently decreasing in size. Anteroventral projection of gena slightly projecting anteriorly, somewhat flattened, surface smooth. Postcoila short, not extending to lateral margin of gena. Subgenal carina with multiple small spinules. Crown with 14–15 regularly distributed spines; dorsalmost and three ventralmost smaller; largest spine 0.12–0.13 mm long. Seta 16-C situated mesially from crown. Mandible with darkly pigmented teeth; apical tooth length 2.35 (2.00–2.67) times that of first dorsal tooth; seta 3-Mn 0.22 (0.20–0.24) times length of 4-Mn; lacinia mobilis with 7 blades; mandibular lobe well-developed, darkly pigmented, apart from teeth. Sensilla: 9-C short, fan-like; 10-C elongate, simple; 11-C short, simple; 12-C elongate, simple; 13-C short, fan-like; 14-C short, simple; 15-C moderately elongate, fan-like; 16-C elongate, simple. 0a-Mn short, bifurcated; 0b-Mn moderately elongate, simple. 6-Mx short, fan-like; 4-Mx short, fan-like; 5-Mx short, fan-like.

SIPHON. 0.41 (0.39–0.42) mm long. Seta 1 forked, situated at 0.16 (0.14–0.18) of length from base; 6-S pale, 9-S lightly pigmented; length of 6-S/9-S: 0.84 (0.76–0.97).

Pupa (n = 4)

EXUVIA ( Amaral & Pinho 2015: 282, fig. 22). Lightly pigmented, yellowish, posterolateral projections of abdomen more darkly pigmented; all setae pale.

CEPHALOTHORAX. Length 1.49 mm (1.46–1.54). Respiratory organ ( Amaral & Pinho 2015: 282: fig. 23) flattened, wide and trilobed, 0.71 mm (0.68–0.78) long cephalocaudad. Dorsal seta 1 short, moderately thick, about three lengths apart from dorsal 2; dorsal 2 of same thickness, about 3.5 times as long as dorsal 1; both arising from undifferentiated cuticle. Metathoracic, supraalar sensilla absent.

ABDOMEN ( Amaral & Pinho 2015: 282, fig. 24). Moderately elongate, tapering, integument rough dorsolaterally; length of segments I–VIII 1.39 mm (1.27–1.44), width/length 0.65 (0.63–0.69). Margins serrate, strongly projected posterolaterally. Dorsal and lateral setae minute, equal from II–VII. Largest seta D-7-VI, 0.56 (0.46–0.60) times length of segment. Terminal process elongate, basal width 0.43 (0.37–0.47) of length, with moderately broad paddles; D-1-IX somewhat short, of intermediate thickness, at about 0.5 length from base; apical spine not articulated; lacking ventroapical seta V-1-IX; female genital lobes round, occupying most of basal portion, elongate in male, extending shortly beyond base. Chaetotaxy as illustrated.

Distribution and biology

The specimens from Santa Catarina have previously been recorded in Amaral & Pinho (2015) and were collected as immatures from the margins of small streams and ground pools in forested areas. This species is newly recorded in Northeast Brazil and the state of Bahia, from two individuals collected in a small stream of a streamside forest in Rio de Contas municipality at 1579 m a.s.l. Rio de Contas is in the Espinhaço mountain range, which comprises the Chapada Diamantina National Park, a hotspot for conservation with many endemic species, with two new ones described here, Corethrella pindorama sp. nov. and C. fuscifimbria sp. nov.

Corethrella alticola is also known from the Brazilian states of GO, RJ, RS, SC, and SP, at altitudes ranging from 80 to 1736 m a.s.l. ( Amaral & Pinho 2015; Borkent 2008).

Remarks

The pupae of C. alticola may be indistinguishable from those of C. manaosensis (not examined in the present work). From the original description in Lane & Cerqueira (1958), as well as the brief description and the photograph present in Borkent (2008), the only clear difference found was regarding the coloration of the exuviae, which can be subtle. The pupal exuviae of C. alticola seem to be, overall, paler (with somewhat darker abdominal projections) and to have a yellowish coloration, while those of C. manaosensis appear to be more darkly pigmented and brown-colored. Although Lane & Cerqueira (1958) defined the pupal abdomen as having “posterior corners with blunt point”, it does not appear to have strong lateral projections in the photograph in Borkent (2008), and the author did not consider that to be the case in his character analysis ( Borkent 2008: 220, character 57). A more detailed description of C. manaosensis should resolve the issue.

On the other hand, adults of Corethrella alticola are very distinctive. They are easily recognized by their unique pigmentation pattern and size (having the second largest wingspan of the family, only shorter than that in C. novaezealandiae Tonnoir, 1927 ). Also, the compound eye coloration and the densely setose postgenal row were not found in any other examined species in the present paper. The specimens from Rio de Contas (Bahia State) do not have the postgenal row as setose as those from Santa Catarina, bearing about 18 setae, which is nevertheless a larger number than in most of the other examined species. The female specimen from Bahia also has a somewhat shorter flagellomere I ( Fig. 15B ). Despite the differences in the postgenal row and the antenna, no further significant variation was found between the specimens from Santa Catarina and Bahia in adults or immatures. Therefore, this variation was considered intraspecific.

Figures

Fig. 15. Corethrella alticola Lane, 1939. A. Pedicel and flagellomeres of female adults from Santa Catarina, lateral view. B. Pediecel and flagellomeres of adult female from Bahia, lateral view. C. Cranial setae, anterior and posterior views, and female clypeus in anterior view. D. Adult thoracic setae, lateral view; black = dorsocentral row; red = prescutal setae; green = antealar setae; blue = supraalar setae. E. Hind leg claw and empodium, lateral view. F. Exuvia of larval head, ventral view, except mandible in dorsal view. Abbreviations: ang = antennal groove; cr = crown; gen = gena; lmpo = postmentum; lmpr = prementum; pot = postcoila; sgc = subgenal carina; 9–16-C = cranial setae; 0(a, b), 3, 4-Mn = mandibular setae, 4–6-Mx = maxillary setae.