Corethrella (Corethrella) blanda Dyar, 1928

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 : 41-44

Corethrella (Corethrella) blanda Dyar, 1928

Fig. 18 ; Appendix 1

Diagnosis

Larva Only extant ground-dwelling species with the following combination of characters: darkly pigmented tergal plates ( Fig. 18D ); a darkly colored mandibular lobe ( Fig. 18D ); head and body light brown ( Fig. 18D ); ventral margin of antennal groove with about 5 moderately developed denticles ( Fig. 18E ); subgenal carina with smooth surface ( Fig. 18E ).

Pupa

Only extant ground-dwelling species with the following combination of characters: a flattened, wide respiratory organ ( Fig. 18G ); abdominal margins strongly expanded laterally and shortly expanded posteriorly ( Fig. 18H ), with pale elongate setae on apex of expansions; abdominal segment III with one elongate lateral seta ( Fig. 18H ).

Material examined

BRAZIL – Santa Catarina State • 1 ♀, adult, with larval and pupal exuviae; Florianópolis, Rio Tavares, Morro do Lampião , Poço de captação; 27°39ʹ56ʺ S, 48°29ʹ29ʺ W; 78 m a.s.l.; 21 Feb. 2018; A.P. Amaral leg.; hand net; CE-MHS • 1 ♀, adult; Santo Amaro da Imperatriz, Plaza Caldas ; 27°44ʹ31ʺ S, 48°48ʹ06ʺ W; 470 m a.s.l.; 1 Apr. 2013; A. Ambrozio-Assis leg.; frog-call trap ( Physalaemus cuvieri ) 1ª3; CE-MHS • 1 ♀, adult; Porto Belo, Ponta do Araçá , “brejo de altitude” [altitude marsh]; 27°07ʹ38ʺ S, 48°31ʹ20ʺ W; 115 m a.s.l.; 25Apr. 2012; L. C. Pinho leg.; Shannon; CE-MHS • 2 ♀♀,adults; Florianópolis, Lagoa do Peri, Saquinho ; 27°43ʹ23ʺ S, 48°30ʹ29ʺ W; 13 m a.s.l.; 8 Apr. 2011; A. Ambrozio-Assis leg.; CDC trap; CE-MHS .

Description

Female adult (n = 5)

HEAD. Sensilla ( Fig. 18A ): Ocular row with 2 thick offset setae at ventral part, about 10–14 more dorsally, extending shortly beyond vertex. Subocular row not well-defined anteriorly, with about 4 posterior slender setae; vertex with a few additional slender setae. Postgenal row with 7–13 slender setae ranging from mid-posterior portion to ventromedially. With 1 thick ventromedial seta.

THORAX. Sensilla ( Fig. 18B ): Antepronotum without setae. Postpronotum with 1 thick dorsal and 0–3 slender, more posterior setae. Scutum, prescutal area with 3–4 ventral and 2–3 posterodorsal thick setae. Antealar area with cluster of 9–14 thick/intermediate and 3–5 slender setae on posteroventral portion. Supraalar area with 3 thick and 2–5 slender setae on ventral portion. Dorsocentral row, posterior part with 6–8 thick offset, longitudinally aligned setae; 26–35 thick/intermediate and 16–18 slender setae completing row. Scutellum with 8–10 thick setae. Posterior anepisternum with 0–2 dorsal setae. Anepimeron bare.

WING. R 3 /R 1: 0.67 (0.65–0.73); R 2+3 /R 2: 0.35 (0.32–0.39).

LEGS ( Fig. 18C ). Empodium of intermediate length, thick, with about 8 branches. Ta1/Ta2: 2.52 (2.28– 2.67); Ta3/Ta4: 1.27 (1.09–1.38).

Larva (n = 1)

EXUVIA ( Fig. 18D ). Uniformly light brown with darkly pigmented tergal plates on I–VII.

HEAD ( Fig. 18E ). Roughly triangular shape in dorsoventral view, 1.26 times as wide as long. Antenna length 0.59 times as long as head; antennal groove 1.31 times length of antenna. Ventral margin of antennal groove with about 5 moderately developed denticles. Postmentum with wide base, strongly tapering distally, 1.73 times as wide as long; 0.37 times length of head. Prementum straight, with 13 triangular teeth, darkly pigmented, central one largest, remaining gently decreasing in size.Anteromedial margin of gena somewhat projected anteriorly, surface smooth. Postcoila short, not extending to lateral margin of gena. Subgenal carina with smooth surface. Crown with 14 regularly distributed spines; 3 dorsalmost and 3 ventralmost smaller; largest spine 0.10 mm long. Seta 16-C situated mesially from crown. Mandible with darkly pigmented teeth; apical tooth length 1.89 of first dorsal tooth; seta 3-Mn 0.31 length of 4-Mn; lacinia mobilis with 8 blades; mandibular lobe well-developed, darkly pigmented, apart from teeth. Sensilla: 9-C short, fan-like; 10-C elongate, simple; 11-C short, fan-like; 12-C elongate, simple; 13-C short, fan-like; 14-C short, fan-like; 15-C short, fan-like; 16-C elongate, simple. 0a-Mn short, fan-like; 0b-Mn elongate, simple. 6-Mx moderately elongated, fan-like; 4-Mx short, simple; 5-Mx moderately elongate, fan-like.

SIPHON. 0.36 mm long. Seta 1 forked, at about 0.19 of length from base; 6-S pale, 9-S lightly pigmented; length of 6-S/9-S: 0.78.

Pupa (n = 1)

EXUVIA ( Fig. 18F ). Uniformly light brown; all setae pale.

CEPHALOTHORAX. Length 1.24 mm. Respiratory organ ( Fig. 18G ) flattened, wide, trilobed, 0.65 mm long longitudinally. Dorsal seta 1 somewhat short, thick, about two lengths apart from dorsal 2; dorsal 2 slender, twice as long as dorsal 1; both setae arising from undifferentiated cuticle. Metathoracic and supraalar setae absent.

ABDOMEN ( Fig. 18H ). Moderately elongate, tapering, integument laterally rough; length of segments I–VIII: 1.24 mm; width/length: 0.65. Margins serrate, strongly projected posterolaterally. Setae D-2 shorter than half length of respective segments, equal from II–VII. Lateral setae L-4 elongate, longer than respective segments. Largest seta L-4-III, 1.29 times length of segment. Terminal process elongate, basal width 0.50 of length, with moderately broad paddles; D-1-IX moderately elongate, of intermediate thickness, at about 0.7 from base; apical spine not articulated; lacking ventroapical seta V-1-IX; female genital lobes broad, occupying most of basal portion. Chaetotaxy as illustrated.

Distribution and biology

The examined specimens have been found in the Atlantic forest of Santa Catarina State, at altitudes ranging from 13 to 470 m a.s.l. Adults were captured with CDC, Shannon and frog-call traps (playing the call of Physalaemus cuvieri ). The single immature collected was found in a small ground pool, inside a highly disturbed forest fragment, at 78 m a.s.l. The specimens from Santo Amaro da Imperatriz have previously been recorded by Ambrozio-Assis et al. (2018).

Corethrella blanda is otherwise known from Costa Rica, Panama, Colombia, Trinidad and Tobago, French Guiana, and the Brazilian states of AM, PA, and SP, at altitudes ranging from 5 to 500 m a.s.l. ( Borkent 2008).

Remarks

The larval exuviae here studied varied from previous descriptions in relation to the number of teeth on the prementum (10 in Dyar 1928; 11 in Lane & Cerqueira 1958), and the number of setae on the crown, described as 10 in Lane & Cerqueira 1958. Those differences are expected given the intraspecific variation observed in other species. In adults, Borkent (2008) described the posterior portion of the dorsocentral row as having two elongate setae somewhat lateral to one another. This is here recognized but differently interpreted. See Morphology remarks.

Figures

Fig. 18. Corethrella blanda Dyar, 1928. A–C. Female adult. A. Cranial setae, anterior and posterior views, and clypeus in anterior view. B. Thoracic setae, lateral view. C. Hind leg claw and empodium. 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 methatorax and abdomen, dorsal and ventral views. Scale bars: 0.2 mm.