Corethrella (Corethrella) bifida Amaral & Pinho, 2023

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 : 14-20

Corethrella (Corethrella) bifida Amaral & Pinho sp. nov.

urn:lsid:zoobank.org:act:36201EFD-D177-4606-9EF9-5DCEA6420FF1

Figs 5–7

Diagnosis

Male and female adult

Only extant species of Corethrella with the following combination of characters: plain wing ( Fig. 5F ); thorax uniformly medium brown ( Fig. 5D ); ventral portion of posterior anepisternum triangular-shaped ( Fig. 5D ); uniformly brown legs, except for the hind femur with about the basal 0.7 pale, trochanter of foreleg and base of forefemur equally pigmented ( Fig. 5E ); empodia short, slender and Y-shaped ( Fig. 6E ).

Larva

Only extant species with the following combination of characters: darkly pigmented tergal plates ( Fig. 7A ); a darkly colored mandibular lobe; most of head, segment X and siphon darkly colored ( Fig. 7C ), but postmentum pale ( Fig. 7A ); crown with 13–14 short spines (shorter than 0.05 mm) evenly spaced ( Fig. 7B ).

Pupa

Only extant species with the following combination of characters: a flattened, wide, trilobed respiratory organ ( Fig. 7E ); a strongly tapered and short abdomen, with paddles short and narrow; abdominal margins moderately expanded posterolaterally, with lateral setae well-developed, longer than each segment ( Fig. 7F ).

Etymology

The specific epithet – bifida – refers to the bifid empodium of the adults of this species.

Material examined

Holotype

BRAZIL – Santa Catarina State • ♂, adult, with pupal and larval exuviae; Palhoça, PEST , Lago da sede ; 27°50ʹ36ʺ S, 48°37ʹ25ʺ W; 7 m a.s.l.; 29 Jun. 2013; A.P. Amarai et al. leg.; hand net; MZUSP.

Allotype

BRAZIL – Santa Catarina State • ♀, adult, with pupal and larval exuviae, same collection data as for holotype, except 28 Oct. 2013; V. Freitas leg.; MZUSP.

Paratypes

BRAZIL – Santa Catarina State • 1 ♀, adult, with pupal and larval exuviae; same collection data as for allotype; CE-MHS • 1 ♂, adult, with pupal and larval exuviae; same collection data as for allotype; CE-MHS • 1 ♀, adult, with pupal and larval exuviae; Santo Amaro da Imperatriz, Pagará , Colônia Santa Luzia ; 27°38ʹ31ʺ S, 48°45ʹ17ʺ W; 51 m a.s.l.; 12 Feb. 2016; Pinho, Amaral and Scarpa leg.; hand net in pond; CE-MHS . – Bahia State • 1 ♀, adult, with pupal and larval exuviae; Maracás, Fazenda Regi Flores ; 13°27ʹ03ʺ S, 40°20ʹ24ʺ W; 856 m a.s.l.; 7 Jun. 2019; A.P. Amaral leg.; hand net in pond; CE-MHS .

Description

Male adult (n = 2)

HEAD ( Fig. 5A ). Medium/dark brown. Outline in anterior view laterally elongate, about 1.45–1.53 times as wide as long. Coronal suture complete, reaching ventral margin of interocular space. Clypeus ( Fig. 5B ) squarish, 1.00–1.17 as wide as long, with 19 intermediate thickness setae. Palpus (as Fig. 6A ) as dark as head, third segment swollen at midlength, 1.3 times length of fifth. Antenna: pedicel medium brown, flagellum uniformly medium brown, flagellomeres (as Fig. 6B ) I very elongate, II and III moderately elongate; flagellomere XIII apically bifurcated. Sensilla coeloconica distribution: 1(II, VII–XIII), 4(I). Sensilla ( Fig. 6C ): Ocular row with 2 thick offset setae at ventral part, almost lateral to one another, and 7–9 thick setae extending shortly beyond vertex. With subocular row of 8–10 slender setae. Postgenal row with 7–8 slender setae, ranging from mid-posterior to ventrolateral portions. With 1 ventromedial thick seta.

THORAX ( Fig. 5D, E ). Uniformly medium brown. Prescutal suture very short. Anterior anepisternum divided longitudinally by sinuous suture. Posterior anepisternum divided by a diagonal suture, inferior portion triangular with anterodorsal margin thick. Sensilla ( Fig. 6D ): Antepronotum with 0–3 slender anterior setae. Postpronotum with 1 thick dorsal and 1 intermediate seta more posteriorly. Scutum, prescutal area with 1 thick ventral seta, 2 intermediate ones dorsally, 2 intermediate more anteriorly. Antealar area, with cluster of 3–4 thick and 5–7 intermediate setae on posteroventral portion. Supraalar area with 2 thick, 1 intermediate and 3–4 slender setae on ventral portion. Dorsocentral row, posterior part with 5 thick offset, longitudinally aligned setae; 8–12 thick and about 19–27 intermediate/slender setae filling row. Scutellum with 10–12 thick setae. Posterior anepisternum with 1–2 slender setae at dorsal part.Anepimeron 5–8 slender setae located middorsally.

WING ( Fig. 5C, F ). Medium brown, somewhat reddish. non-marginal veins with well-developed scales. Without pattern of pigmentation. Apex of R 2 equal to apex of M 1. Halter as pigmented as scutellum. R 3 /R 1: 0.61–0.65; R 2+3 /R 2: 0.43–0.50.

LEGS ( Fig. 5E ). Medium brown, with hind femur basal 0.7 lighter. Tibiae, femora with well-developed scales. Midleg tarsomeres 1–3 with thick subapical setae. Apices of fore-, midtarsi bilobed. Tarsal claws of foreleg and midleg unequal, midleg ones largest, hind claws shortest. Empodium ( Fig. 6E ) short, slender, with 1 branch. Ta1/Ta2: 2.66–2.84; Ta3/Ta4: 1.20–1.25.

ABDOMEN. Uniformly medium brown.

GENITALIA ( Fig. 5G, I ). Gonocoxite pigmented, ovate; without distinctively elongate spicules on anteromedial area; dorsal row well-defined, with 5 thick setae restricted to dorsal region, 3 anterior ones with apex flattened and expanded, 2 posterior more slender; with 2 dorsomedial stout setae, anterior seta bolder, tapering at apex, located at 0.60–0.64 from base; both setae with elongate filamentous apex and united basally by sclerotized plate. Gonostylus thick, with constant width, subbasal seta simple and elongate, ventrally located; apical seta short and simple. Aedeagus ( Fig. 5H ) squat, with wide base, margins fused at apex.

Female adult (n = 4)

As for male, except:

HEAD ( Fig. 6F ). Clypeus ( Fig. 6C ) 1.17 (1.13–1.29) times as wide as long, with 12–15 dorsal setae, 3 central ones thickest. Mandibles serrate. Antenna as in Fig. 6G . Sensilla coeloconica distribution: 1(II, VI–XIII), 4(I).

WING ( Fig. 6H–I ). R 3 /R 1: 0.78 (0.76–0.80); R 2+3 /R 2: 0.33 (0.30–0.35).

LEGS. Tarsi undivided; tarsal claws of each leg equal to those of others; equal on each leg, simple. Ta1/ Ta2: 2.76 (2.64–2.84); Ta3/Ta4: 1.25 (1.18–1.32).

ABDOMEN ( Fig. 6J ). Uniformly medium brown.

Larva (n = 6)

EXUVIA ( Fig. 7A ). Head, segment X, siphon dark brown; postmentum, ventral part of gena pale; mandibles darker than cranial sclerites. With dark brown tergal plates on abdominal segments I–VII.

HEAD ( Fig. 7B ). Elongate triangular shape in dorsoventral view, 1.20 (1.17–1.25) times as wide as long. Antenna 0.56 (0.50–0.57) times length of head; antennal groove 1.45 (1.31–1.68) times length of antenna; ventral margin of antennal groove with about 5 large denticles. Postmentum with base wide, strongly tapering, 1.84 (1.76–1.90) times as wide as long; 0.33 (0.30–0.35) times length of head. Prementum straight, with 13 triangular-shaped teeth, darkly pigmented, central one largest, remaining gently decreasing in size. Anteroventral projection of gena slightly projecting anteriorly, with anterior margin flat, surface irregular. Postcoila short, not extending to lateral margin of gena. Subgenal carina with smooth surface. Crown with 13–14 spines, regularly distributed, with two dorsalmost, two ventralmost spines smaller; largest spine 0.04–0.05 mm in length; seta 16-C situated mesially from crown. Mandible with darkly pigmented teeth; apical tooth 1.69 (1.50–1.88) times length of first dorsal tooth; seta 3-Mn 0.25 (0.22–0.29) times length of 4-Mn; lacinia mobilis with 7 blades; mandibular lobe well-developed, darkly pigmented, apart from teeth. Sensilla: 9-C moderately elongate, bifurcated; 10-C elongate, simple; 11-C short, fan-like; 12-C elongate, simple; 13-C short, fan-like; 14-C short, simple, thick; 15-C short, fan-like; 16-C elongate, simple. 0a-Mn short, simple; 0b-Mn elongate, simple. 6-Mx short, forked; 4-Mx short, fan-like; 5-Mx moderately elongate, fan-like.

SIPHON ( Fig. 7C ). 0.24 mm (0.20–0.27) long; seta 1 forked, situated at 0.28 (0.21–0.37) of length from base; 6-S, 9-S lightly pigmented; length of 6-S/9-S: 0.86 (0.84–0.88).

Pupa (n = 6)

EXUVIA ( Fig. 7D ). Medium brown, with medial portion of abdominal segments II–VII darker; all setae lightly pigmented.

CEPHALOTHORAX. Length 1.12 mm (1.03–1.22). Respiratory organ ( Fig. 7E ) flattened, wide and trilobed, 0.74 mm (0.65–0.85) long longitudinally. Dorsal seta 1 short, thick, about two lengths from dorsal 2; dorsal seta 2 slender, about two times as long; both setae arising from undifferentiated cuticle. Sensilla supraalar 2, metathoracic 1–2 absent.

ABDOMEN ( Fig. 7F ). Short and strongly tapered posteriorly, integument rough laterodorsally; length of segments I–VIII 0.86 mm (0.78–0.94); width/length: 0.91 (0.87–0.97). Margins smooth, moderately expanded laterally, somewhat posteriorly. Setae D-2 short, about half length of respective segments, subequal from II–VII. Lateral setae L-4 long, thick from II–VII, largest on IV, 1.11 (0.99–1.28) times as long as segment. Terminal process short, basal width 0.66 (0.62–0.72) times length, with narrow paddles; D-1-IX short, located at about 0.45 from base; apical spine not articulated; lacking a ventroapical seta V-1-IX; female genital lobe tapering, occupying most of basal portion, male ovate, slightly extending beyond base. Chaetotaxy as illustrated.

Distribution and biology

All specimens studied were collected as immatures in ponds, at altitudes ranging from 6 to 856 m a.s.l. In Santa Catarina State, the locations comprised an area of sandy coastal vegetation (restinga) in Palhoça municipality and a small farm in Santo Amaro da Imperatriz. In Bahia, Maracás municipality, it consisted of an area of transition between rainforest (Atlantic forest biome) and xeric shrubland (caatinga biome). These data suggest a preference for oviposition in open areas, which should be confirmed with further collections. The serrate mandibles of females indicate they feed on frog blood in nature.

Remarks

Males and females from Santa Catarina and Bahia have previously been identified as Corethrella davisi Shannon & Del Ponte, 1928 but were later associated through the diagnostic features of the immatures. Adults of C. bifida sp. nov. are very similar to those of C. davisi , differing in the morphology of the empodia (two branches in C. davisi ), females without sensilla coeloconica on flagellomeres III and V, and the more distal position of the first dorsomedial seta on male genitalia, which is also the greatest distance from the base recorded for the family (this may require further confirmation, since all examined male genitalia were in poor condition and measurements could have been imprecise). Immatures, in turn, present many distinctive features, such as the pale and relatively more elongate larval postmentum, crown spines in larger number and evenly distributed (ventrally sparse in C. davisi ), seta 9-C elongate and bifurcate (short and fan-like in C. davisi ); pupa with a more elongate abdomen, margins expanded posterolaterally, with well-developed lateral setae on segments III–VII.

Figures

Fig. 5. Corethrella bifida sp. nov., male adult, holotype (MZUSP). A. Head, anterior view. B. Clypeus, anterior view.C. Wing veins.D. Detail of thorax, lateral view.E. Thorax and legs in lateral view.F. Wing. G. Gonocoxite and gonostylus, dorsal view. H. Aedeagus, dorsal view. I. Genitalia, dorsal view. Scale bars: 0.1 mm.

Fig. 6. Corethrella bifida sp. nov., female adult, allotype (MZUSP). A. Left palpus, lateral view. B. Flagellomeres and pedicel, lateral view. C. Cranial setae, anterior and posterior views, and clypeus in anterior view. D. Thoracic setae, lateral view. E. Hind leg claw and empodium, lateral view. F. Head, anterior view. G. Antenna, lateral view. H. Wing. I. Wing veins. J. Abdomen, lateral view. Scale bars: 0.1 mm.

Fig. 7. Corethrella bifida sp. nov., larva and pupa. A. Larval exuvia, ventral view. B. Exuvia of larval head, ventral view, except mandible in dorsal view. C. Siphon of larva, dorsal view. D. Pupal exuvia, dorsal view. E. Pupal respiratory organ, dorsal view. F. Pupal metathorax and abdomen, dorsal and ventral views. Scale bars: 0.2 mm.