Corethrella (Corethrella) infuscata 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 : 62-65

Corethrella (Corethrella) infuscata Lane, 1939

Fig. 30 ; Appendix 1

Diagnosis

Larva

(Possibly indistinguishable from Corethrella tarsata Lane, 1942 ; see Discussion). Only bromeliculous species with the following combination of characters: head, segment X, and siphon light to medium brown ( Fig. 30D ); postmentum elongate, with margins tapering from base ( Fig. 30E ); prementum with 13–14 darkly pigmented teeth, mesial one largest, remaining teeth subequal ( Fig. 30E ); ventral margin of antennal groove smooth ( Fig. 30E ).

Pupa

Only bromeliculous species with the following combination of characters: exuvia medium brown, with medial portion of abdominal segments III–VII slightly darker ( Fig. 30F ); abdomen somewhat ovate ( Fig. 30H ); dorsal setae not well-developed (shorter than respective segments), lateral setae weakly developed on III–IV, moderately developed on V–VIII ( Fig. 30H ); respiratory organ short tubular, expanded at apex, with trachea spiraled ( Fig. 30G ).

Material examined

BRAZIL – Santa Catarina State • 1 ♀, 1 ♂, adults, with larval and pupal exuviae; Grão Pará, Parque Estadual Serra Furada ; 28°11ʹ26ʺ S, 49°23ʹ30ʺ W; 9 Jun. 2013; L.C. Pinho, A.P. Amaral, M.O. Bessel and A. Will leg.; bromeliad; CE-MHS • 1 ♀, adult, with larval and pupal exuviae; Palhoça, PEST ; 27°50ʹ36ʺ S, 48°37ʹ25ʺ W; 7 m a.s.l.; 16 Aug. 2013; V. Freitas leg.; bromeliad; CE-MHS • 1 ♀, adult, with larval and pupal exuviae; Rebio Arvoredo ; 27°17ʹ32ʺ S, 48°21ʹ41ʺ W; 155 m a.s.l.; 18 Feb. 2016; L.C. Pinho et al. leg.; bromeliad ( Nidularium inocentii ); CE-MHS . – Bahia State • 1 ♂, adult, with larval and pupal exuviae; Maraú, Estrada para Saquaíra ; 13°59ʹ16ʺ S, 38°57ʹ03ʺ W; 21 m a.s.l.; 27 Sep. 2019, A.P. Amaral leg.; bromeliad; CE-MHS • 1 ♂ with larval and pupal exuviae; Maraú, Pontal ; 14°15ʹ60ʺ S, 38°59ʹ55ʺ W; 4 m a.s.l.; 27 Sep. 2019; A.P. Amaral leg.; bromeliad; CE-MHS • 1 ♀, adult, with larval and pupal exuviae; Maraú, Lagoa Butterfly House ; 14°01ʹ39ʺ S, 38°57ʹ02ʺ W; 9 m a.s.l.; 28 Sep. 2019; A.P. Amaral leg.; bromeliad; CE-MHS .

Description

Male and female adults (3 ♂♂, 3 ♀♀)

HEAD. Sensilla ( Fig. 30A ): Ocular row with 2–3 thick offset setae at ventral part, more dorsally 18–22 setae extending to mid-posterior portion of head. Subocular row poorly defined anteriorly, with about 15 setae on posterior portion; interocular space and vertex with variable mumber of slender setae. Postgenal row with 6–14 slender setae, ranging from posterior part of ocular row to ventromedially. With 2 thick ventromedial setae.

THORAX. Sensilla ( Fig. 30B ): Antepronotum with 1 intermediate lateral and 0–7 slender ventral setae. Postpronotum with 1 thick dorsal seta; 1–2 intermediate and 2–3 slender posterior setae. Scutum, prescutal area with about 4–8 intermediate and 3–6 slender setae grouped anteriorly, central cluster of 5–8 thick and 2–4 slender setae. Antealar area with 4–5 thick/intermediate setae vertically arranged next to prescutal suture, 8–11 thick/intermediate ventral setae more posteriorly, forming a U-shape; 14–29 setae surrounded by 12–15 slender setae. Dorsocentral row, posterior part with cluster of 16–23 thick setae, inserted in shallow cuticular depression; 17–19 thick/intermediate and approximately 44–50 slender setae filling row. Scutellum with 12–14 thick setae. Posterior anepisternum bare. Anepimeron with 3–7 slender setae.

WING. Male R 3 /R 1: 0.40 (0.39–0.41); R 2+3 /R 2: 0.86 (0.82–0.90). Female R 3 /R 1: 0.46 (0.46–0.47); R 2+3 /R 2: 0.65 (0.59–0.70).

LEGS. Empodium ( Fig. 30C ) of intermediate length, slender, with 3 branches. Male Ta1/Ta2: 2.87 (2.68– 3.10); Ta3/Ta4: 0.75 (0.73–0.80). Female Ta1/Ta2: 2.69 (2.60–2.82); Ta3/Ta4: 1.03 (1.00–1.08).

Larva (n = 6)

EXUVIA ( Fig. 30D ). Uniformly light to medium brown; without tergal plates.

HEAD ( Fig. 30C ). Wide, triangular in dorsoventral view, 1.26 (1.13–1.37) times as wode as long.Antenna 0.57 (0.54–0.61) times length of head; antennal groove 1.20 (0.98–1.35) length of antenna. Ventral margin of antennal groove without denticles. Postmentum elongate, tapering from base, 1.25 (1.11– 1.45) times as wide as long; length 0.43 (0.39–0.49) of head. Prementum curved, with 13–14 ogival teeth, darkly pigmented, central one largest, remaining ones slightly decreasing in size. Anteroventral projection of gena strongly projected anteriorly, surface smooth. Postcoila extending to lateral margin of gena. Subgenal carina with multiple small spinules. Crown with 11–14 spines, more sparse ventrally, sizes growing towards lateral; largest spine 0.08–0.13 mm long. Seta 16-C somewhat anterolateral to crown. Mandible with darkly pigmented teeth; apical tooth length 1.53 (1.33–1.86) of first dorsal tooth; seta 3-Mn 0.37 (0.34–0.40) times length of 4-Mn; lacinia mobilis with 7–8 blades; mandibular lobe well-developed, pale, contiguous to teeth. Sensilla: 9-C short, fan-like; 10-C elongate, simple; 11-C elongate, simple, bifurcated or forked; 12-C elongate, simple; 13-C short, fan-like; 14-C moderately elongate, simple; 15-C moderately elongate, bifurcated or forked; 16-C elongate, simple. 0a-Mn short, fan-like, or moderately elongate bifurcated; 0b-Mn elongate, simple. 6-Mx short, simple; 4-Mx short, simple; 5-Mx moderately elongate, bifurcated.

SIPHON. 0.41 mm (0.37–0.44) long. Seta 1 forked, at 0.17 (0.13–0.21) of length from base; 6-S pale, 9-S darkly pigmented; length of 6-S/9-S: 0.59 (0.50–0.67).

Pupa (n = 6)

EXUVIA ( Fig. 30F ). Medium brown, with medial portion of abdominal segments III–VII slightly darker; setae moderately pigmented, with cephalothorax dorsal 1 apparently lighter.

CEPHALOTHORAX. Length 1.52 mm (1.46–1.59). Respiratory organ ( Fig. 30G ) tubular, short, swollen at midlength, with enlarged apical opening and spiraled trachea; 0.14 mm (0.11–0.17) long. Dorsal seta 1 short, slender, 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, simple.

ABDOMEN ( Fig. 30H ). Elongate, somewhat ovate, gently tapering from IV–VII, anterolateral surface of tergites rough; segments I–VIII length 1.57 mm (1.46–1.66), width/length: 0.60 (0.54–0.70). Margins smooth, not expanded laterally. Setae D-2 about half of length of respective segments, equal from III– VII. Lateral setae moderately elongate on I and V–VII, over half length of respective segments. Largest seta L-1-I, 0.69 (0.46–0.90) times length of segment. Terminal process short, basal width 0.79 (0.73– 0.84) of length, with paddles strongly tapering from base; D-1-IX short, located at about 0.65 from base; apical spine articulated; ventroapical seta V-1-IX about 3 times as long as apical spine; female genital lobe tapering at midlength; genital lobe elongate in male, extending through approximately 0.85 of terminal process. Chaetotaxy as illustrated.

Distribution and biology

Corethrella infuscata is newly recorded both from the state of Bahia and from the Brazilian Northeast region. The examined specimens were reared from immatures, collected from bromeliad tanks of Aechmea sp. and Aechmea multiflora L.B.Sm. in Bahia, and Nidularium innocentii Lem. on Arvoredo Marine Biological Reserve, a small island in Santa Catarina State. Vegetation types were sandy coastal vegetation (restinga) and subtropical Atlantic forest, with altitudes ranging from 4 to 155 m a.s.l. The other records of this species are from the Atlantic forests of the Brazilian states of RJ, SC, and SP, at altitudes ranging from 0 to about 400 m a.s.l. ( Borkent 2008; Ambrozio-Assis et al. 2018).

Remarks

The studied adult specimens keyed out to, and fairly matched the description of, Corethrella infuscata ; however, there was considerable variation with respect to the chaetotaxy. Three individuals possessed two thick ventral setae in the ocular row (four elongate setae on the frons, in Borkent’s terminology; Borkent 2008). The number of those setae is frequently used as a diagnostic feature and is usually constant among species. Apparently, at least C. infuscata has some variation, or it may be that those specimens belong to an unrecognized species. Other relevant differences in relation to previous descriptions are the number of setae on the scutellum (10 in Lane 1942) and the posterior setae on dorsocentral row (described as 12 by Borkent 2008). Despite those differences, immatures and adults satisfactorily match the descriptions. A unique feature, present in adults of Corethrella infuscata , C. fulva Lane, 1939 and possibly C. tarsata Lane, 1942 and C. unisetosa Borkent, 2008 due to their close relashionship, is the posterior setae on the dorsocentral row being situated inside a cuticular depression, delimited by a faint margin.

Lane & Aitken (1956) described the immatures of Corethrella tarsata and, from the illustration and details provided, it was not possible to distinguish the larva from that of C. infuscata . A more detailed description should enable such a distinction in the future.

Figures

Fig. 30. Corethrella infuscata 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, dorsal view. G. Pupal respiratory organ, dorsal view. H. Pupal metathorax and abdomen, dorsal and ventral views. Scale bars: 0.2 mm.