Corethrella (Corethrella) fulva 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 : 66-69

Corethrella (Corethrella) fulva Lane, 1939

Fig. 31 ; Appendix 1

Diagnosis

Larva

Only bromeliculous species (one record of a ground-dwelling specimen) with the following combination of characters: exuvia pale ( Fig. 31D ); postmentum elongate, with margins tapering from base ( Fig. 31E ); prementum with 13 darkly pigmented teeth, mesial one largest, alternating laterally between larger and smaller teeth ( Fig. 31E ).

Pupa

Only New World species with cephalothorax darkly pigmented and pale abdomen ( Fig. 31F ); abdominal dorsal setae III–IV longer than respective segments, remaining weakly developed ( Fig. 31H ).

Material examined

BRAZIL – Santa Catarina State • 1 ♂, adult, with pupal exuvia; Bombinhas, Zimbros, Praia vermelha ; 27°12ʹ06ʺ S, 48°34ʹ13ʺ W; 18 m a.s.l.; 15 Oct. 2011; Fabris and Ganzer leg.; bromeliad; CE-MHS • 1 ♂, adult; Rebio Arvoredo ; 27°17ʹ30ʺ S, 48°22ʹ01ʺ W; 26 m a.s.l.; 17 Feb.–9 Apr. 2016; L.C. Pinho et al. leg.; Malaise trap; CE-MHS • 1 ♂, adult, with pupal exuvia; Santo Amaro da Imperatriz, Plaza Caldas , weir; 27°44ʹ01ʺ S, 48°48ʹ47ʺ W; 22 Jul. 2014; L.C. Pinho, A.P. Amaral, V. Gonçalves and P.L. Scarpa leg.; bromeliad; CE-MHS . – Bahia State • 1 ♂, adult, with pupal exuvia; Porto Seguro, RPPN Veracel , muçununga, pools; 16°21ʹ33ʺ S, 39°08ʹ15ʺ W; 72 m a.s.l.; 31 Aug. 2019; A.P. Amaral leg.; hand net; CE-MHS • 1 ♀, adult, with larval and pupal exuviae; Porto Seguro, RPPN Estação Veracel , Trilha 12-09; 16°19ʹ36ʺ S, 39°07ʹ26ʺ W; 74 m a.s.l.; 28 Aug. 2019; A.P. Amaral leg.; bromeliad; CE-MHS • 1 ♀, adult, with larval and pupal exuviae; Ilhéus, Cabruca da UESC ; 14°47ʹ33ʺ S, 39°10ʹ23ʺ W; 38 m a.s.l.; 5 Sep. 2019; A.P. Amaral leg.; stream; CE-MHS • 1 ♀, adult, with larval and pupal exuviae; Ilhéus, Jóia do Atlântico ; 14°38ʹ27ʺ S, 39°03ʹ55ʺ W; 6 m a.s.l.; 15 Apr. 2020; A.P. Amaral leg.; bromeliad; CE-MHS .

Description

Male and female adults (4 ♂♂, 3 ♀♀)

HEAD. Sensilla ( Fig. 31A ): Ocular row with 2 thick offset setae at ventral part, more dorsally with 15–18 setae extending to mid-posterior portion of head. Subocular row poorly defined anteriorly, with about 4–6 setae on posterior portion. Interocular space and vertex with many slender setae. Postgenal row with 7–9 slender setae, ranging from posterior part of ocular row to ventromedially. With 2–3 thick ventromedial setae.

THORAX. Sensilla ( Fig. 31B ):Antepronotum with 4–10 intermediate, slender ventral setae.Postpronotum with 1 thick dorsal seta; 1 thick and 0–3 slender setae more posteriorly.Scutum, prescutal area with about 3–7 thick/intermediate setae grouped anteriorly; 1 thick ventral and 2 thick dorsal setae more posteriorly. Antealar area with 6–7 thick/intermediate setae vertically arranged, next to prescutal suture; 7–9 thick/ intermediate ventral setae more posteriorly, forming a U-shape; 11–20 spread slender setae, with a group near dorsocentral row. Supraalar area with 2–3 thick and 1–2 intermediate setae logitudinally aligned, surrounded by about 7–15 slender setae. Dorsocentral row, posterior part with cluster of 15–21 thick setae, inserted in a shallow cuticular depression; 23–28 thick/intermediate and approximately 28–40 slender ones filling row. Scutellum with 13–14 thick setae. Posterior anepisternum bare. Anepimeron with 5–9 slender setae.

WING. Male R 3 /R 1: 0.41 (0.38–0.46); R 2+3 /R 2: 0.80 (0.65–0.90). Female R 3 /R 1: 0.50 (0.49–0.51); R 2+3 / R 2: 0.58 (0.50–0.63).

LEGS. Empodium ( Fig. 31C ) of intermediate length, slender, with 3 branches. Male Ta1/Ta2: 3.26 (3.13– 3.53); Ta3/Ta4: 0.70–0.70. Female Ta1/Ta2: 3.00 (2.94–3.06); Ta3/Ta4: 1.05 (1.00–1.09).

Larva (n = 3)

EXUVIA ( Fig. 31D ). Uniformly pale; without tergal plates.

HEAD ( Fig. 31E ). Wide, roughly triangular in dorsoventral view, 1.20 (1.17–1.25) times as wide as long. Antenna 0.51 (0.50–0.52) times length of head; antennal groove 1.23 (1.14–1.31) times length of antenna. Ventral margin of antennal groove without well-developed denticles, with a few minute spinules. Postmentum elongate, gently tapering from base to midlength and more abruptly distally; 1.14 (1.09–1.19) times as wide as long; length 0.47 (0.46–0.49) of head. Prementum somewhat curved, with 13 triangular darkly pigmented teeth, central one largest, second small, third large, fourth smaller, fifth large and remaining gradually smaller. Anteroventral projection of gena strongly projected anteriorly, surface smooth. Postcoila extending to lateral margin of gena. Subgenal carina with multiple small spinules. Crown with 14–18 spines, regularly distributed, sizes growing towards lateral, ventral spines shortest; largest spine 0.10–0.12 mm long. Seta 16-C somewhat anterolateral to crown. Mandible with darkly pigmented teeth; apical tooth length 2.06 (2.00–2.17) times that of first dorsal tooth; seta 3-Mn 0.43 (0.39–0.49) times length of 4-Mn; lacinia mobilis with 7 blades; mandibular lobe well-developed, pale, contiguous to teeth. Sensilla: 9-C moderately elongate, fan-like; 10-C elongate, simple; 11-C elongate, bifurcated; 12-C elongate, simple; 13-C short, fan-like; 14-C moderately elongate, simple; 15-C moderately elongate, simple or forked; 16-C elongate, simple. 0a-Mn short, fan-like; 0b-Mn elongate, simple. 6-Mx short, simple; 4-Mx short, simple; 5-Mx short, fan-like.

SIPHON. 0.23 mm (0.21–0.24) long. Seta 1 bifurcated, at about 0.30 of length from base; 6-S pale, 9-S darkly pigmented; length of 6-S/9-S: 0.58 (0.55–0.61).

Pupa (n = 6)

EXUVIA ( Fig. 31F ). Cephalothorax dorsally pale, dark brown ventrally; metathorax and segments I and II uniformly dark brown; segments III–VIII and terminal process light/medium brown, more darkly pigmented mesially; setae moderately pigmented, with cephalothorax dorsal 1 apparently paler.

CEPHALOTHORAX. Length 1.38 mm (1.20–1.44). Respiratory organ ( Fig. 31G ) tubular, short, swollen at midlength, with narrow apical opening; trachea not spiraled; 0.11 mm (0.10–0.13) long. Dorsal seta 1 short, somewhat thick; about two lengths apart from dorsal 2; dorsal 2 slender, about three times as long; both setae arising from undifferentiated cuticle. Metathoracic 2 and supraalar 2 sensilla present. Metathoracic seta 1 elongate and simple.

ABDOMEN ( Fig. 31H ). Elongate, somewhat ovate, gently tapering from IV–VII, surface of tergites smooth; length of segments I–VIII: 1.38 mm (1.17–1.51), width/length: 0.54 mm (0.51–0.58). Margins smooth, not expanded laterally. Setae D-2 elongate on III–IV, shorter on V–VII. Lateral setae slender and elongate on I, somewhat elongate and thick on V–VII. Largest seta D-2-III, 1.78 (1.56–1.94) times length of segment. Terminal process short, basal width 0.83 (0.65–0.91) of length, with paddles strongly tapering from base; D-1-IX elongate, located at about 0.60 from base; apical spine articulated; ventroapical seta V-1-IX about two times as long as apical spine; female genital lobe tapering at midlength; genital lobe elongate in male, extending almost to level of apical spine. Chaetotaxy as illustrated.

Distribution and biology

The examined specimens of Corethrella fulva were reared from immatures collected from tanks of both epyphitic and ground level Aechmea sp. and Vriesea sp. bromeliads, and from ground pools. Sampled localities were Atlantic forest areas in Bahia and Santa Catarina states, at altitudes ranging from 18 to 72m a.s.l. The specimens from Santa Catarina have previously been reported by Amaral et al. (2019).

It has also been recorded from the Atlantic forest in the states of BA, RJ, SC, and SP, at altitudes ranging from 0 to 880 m a.s.l. ( Borkent 2008; Amaral et al. 2019).

This is the first record of this species occurring in ground pools. Borkent (2008: 251) discussed the habitat diversification of Corethrellidae , arguing that species are restricted to certain types of habitats, distinguished by him as ground-dwelling or phytotelmata. These records, along with the specimen of C. davisi found in a bromeliad, may indicate that at least some species may be more flexible that previously thought, or that more than one species may be represented under the same name. Further collections should help solve these questions.

Remarks

Lane (1953) described the pupal respiratory organ as apically expanded; however, in the specimens examined here and in the type specimens deposited in DEFS, it appears to be narrowed at its apex. This difference may be due to preservation, but we consider the morphology of the respiratory organ an important diagnostic feature of the species. Six individuals collected in Lençóis (Chapada Diamantina National Park), Bahia, keyed out to Corethrella fulva but were not included in this study as they may represent an undescribed species, with a uniformly medium brown pupa and one sensillum coeloconicum on each of the flagellomeres (I–II, X–XIII). Two individuals collected in Maraú, Bahia, not included here, also keyed out to this species but had two sensilla coeloconica on each of flagellomeres XII–XIII, as well as uniformly colored pupae. Currently it is not possible to confidently determine whether those individuals are members of C. fulva or a different species.

Figures

Fig. 31. Corethrella fulva Lane, 1939. A. Adult cranial setae, anterior and posterior views, and female clypeus in anterior view. B. Adult thoracic setae, lateral view. C. Hind leg claw and empodium, lateral view. D. Larval exuvia, ventral view. E. Exuvia of larval head, ventral view, except mandible in dorsal view. F. Pupal exuvia, ventral view. G. Pupal respiratory organ, dorsal view. H. Pupal metathorax and abdomen, dorsal and ventral views. Scale bars: 0.2 mm.