Watsonopsestis, László, 2022

László, Gyula M., 2022, Review of theAfrotropical Thyatirinae (Lepidoptera, Drepanidae) with description of a new genus and a new species, Zootaxa 5124 (3), pp. 359-374 : 361-364

Watsonopsestis gen. n. ( Figs 5–8 , 20–21 , 31 )

Type species: Watsonopsestis smithi sp. n., by monotypy.

Diagnosis

The type species of the new genus is highly reminiscent externally of species of the Oriental genus Horipsestis Matumura, 1933 sharing characters such as the nearly identical wingshape and wingpattern with a conspicuously pale basal area, a darkened inner half of the median area, a similar configuration of the transverse lines and the apical streak. The two genera, however, are clearly distinguished in the genital morphology: in the male genitalia, the new genus has a considerably shorter and broader, medio-ventrally largely dilated valva, and a well-developed, rounded, lobe-like, densely setose protrusion of the transtillae, which is absent in Horipsestis , where the transtillae are fused into a knob-like medial plate. Furthermore, the transtillae of Watsonopsestis are connected to the fultura inferior (juxta) with a narrow, sclerotized band, while in Horipsestis , the transtillae and the juxta are unattached. The two genera have markedly different fultura inferiors: that of Watsonopsestis consists of a pair of unattached, broad-based, short, rounded-triangular lobes, whereas in Horipsestis it is comprised of a pair of basally fused, parallel, long and broad, tongue-shaped plates directed caudad. An additional typical character of Horipsestis is the antero-medially broadly depressed vinculum, which is evenly convex in Watsonopsestis . The short, tubular aedeagus, the shape of the carina and the presence of a spinulose cornuti field are homologous characters in the two genera, the only remarkable difference being the presence of a well-developed medial diverticulum of the vesica in Watsonopsestis . In the female genitalia, the most important distinctive character between the two genera is the considerably smaller, less sclerotized, calyculate ostium bursae and the markedly shorter and broader signum bursae of Watsonopsestis , compared to those of the Oriental genus.

Compared to Marplena Lane, 1973 , the other monotypic Afrotropical thyatirine genus, Watsonopsestis has a somewhat slimmer body, a slightly longer and terminally less dilated forewing with a gently arcuate costal margin (it is straight in Marplena ) and a considerably lighter ground colour with a more brownish shade. The dorsal half of the forewing basal area is whitish with pale brownish suffusion in Watsonopsestis , while it is uniformly grey in Marplena . The new genus has a more strongly undulate antemedial line situated further from the wing base and a smaller orbicular and larger reniform stigma which are adjoined to each other, whereas the orbicular and reniform stigma are nearly identical in size and well separated in Marplena . The postmedial line is markedly more arched medially in Watsonopsestis and the subterminal line is weakly defined and interrupted, while it is sharply contrasting in Marplena . The subapical section of the costa bears a black, more or less semi-circular marking in the new genus which is absent in Marplena , while the apical streak is much shorter and thinner in Watsonopsestis .

In the male genitalia, Watsonopsestis has a basally markedly narrower uncus, longer socii, a distally narrower, proximally wider tegumen, and a much shorter, apically more pointed and ventrally more dilated valva compared to Marplena . The transtilla of the new genus bears a rounded-triangular setose lobe which is absent in Marplena . The configuration of the fultura inferior (juxta) is similar in both genera consisting of two small unattached plates, but those of Watsonopsestis are broad-based and rounded-triangular, while they are elongate-quadrangular in Marplena .

The aedeagus of the two genera are similar in shape, but it is slightly longer and straight, and the carina process is more pointed in the new genus than in Marplena . Additionally, the vesica of Watsonopsestis has a well-developed diverticulum medially, which is absent in Marplena .

In the female genitalia, the main differences between Marplena and Watsonopsestis are expressed in the considerably narrower ostium bursae and the markedly larger, elongate signum bursae compared to the small, round signum of Marplena .

Description

External morphology of adult ( Figs 5–8 ). Forewing length 16-17 mm. Antenna filiform, laterally flattened, typical of most Thyatirinae , dorsally covered by a thin layer of small white scales, chequered with dark brown in the basal quarter; scapus short but broad, covered in long, off-white scales with a narrow, black subbasal ring.

Head relatively large, labial palp medium long and narrow, upcurved, dorso-laterally dark brown, ventrally off-white; medial segment ca. 5 times longer than basal and apical segment. Frons greyish-white with a dark brown band anteriorly, vertex pale ochreous-brown. Compound eye relatively large, globular, anteriorly bordered by a thin crista of long, dark brown hair-like scales. Collar pale ochreous sparsely scattered by dark brown scales; tegula bright white basally, gradually darkening towards tip, apex dark brown; both sides of thorax pale greyish-brown, abdomen greyish-white with a long, prominent dark brown dorsal hair-tuft on 3 rd segment.

Forewing. Moderately elongate and narrow, costal and outer margin slightly arched, ventral margin almost straight, apex rounded. Basal and antemedial area greyish-white in dorsal, greyish-brown in ventral half without transverse lines. Antemedial line double, evenly arched, gently wavy. Medial line absent, inner half of median area dark brown, gradually lightened distally. Orbicular stigma contiguous to reniform stigma, former one half as large as latter. Postmedial line double, short costal section straight, then curved outwards in dorsal third, ventral two-thirds almost straight. Subterminal line very thin, interrupted, poorly visible, subterminal area with short black streaks on veins; terminal line thin, dark brown, scalloped between veins. Apical streak very thin and short, slightly curved, ending in vein M1. Cilia long, pale grey, chequered with narrow, dark grey patches. Hindwing. Costal and outer margin arcuate, anal margin almost straight; ground colour pale ochreous-grey in basal half, slightly darkening towards outer margin. Discal spot small, dash-like, diffuse; transverse lines absent, terminal line dark grey; cilia long, pale grey.

Underside of wings uniformly pale grey, transverse lines undiscernible, subapical section of forewing costal margin pale greyish-white.

Intraspecific variability limited. Sexual dimorphism negligible, expressed only by the somewhat longer and broader forewing of female.

Male genitalia ( Figs 20–21 ). Uncus digitiform, moderately long, narrow, apically rounded; socius as long as uncus, rather narrow with rounded apex, directed parallelly with uncus. Tegumen short, very broad dome-shaped anteriorly, narrow trapezoidal posteriorly. Vinculum short, broadly rounded. Valva short, broad at base, dorsal margin gently convex with narrow costal sclerotized band, basal half of ventral margin almost straight, medial section abruptly curved dorsad, distal half evenly concave, apex rounded-triangular. Sacculus very weakly sclerotized, without process. Transtilla well-developed, rounded triangular, lobe-like, distally densely covered in short setae, proximally connected to fultura inferior (juxta) with a narrow, sclerotized band. Fultura superior unmodified, very weakly sclerotized, broad ribbon-like. Fultura inferior consisting of two basally broad, short, rounded-triangular plates with setose apex. Aedeagus short, moderately thick, tubular, coecum long, almost half as long as entire aedeagus, apex rounded; carina short, slightly curved, claw-like. Vesica relatively long, basal part inflated, medial part with a semi-spherical diverticulum and an elongate finely spinulose area, distal section narrow tubular, slightly tapering.

Female genitalia ( Fig. 31 ). Papilla analis short and relatively narrow, rounded, posterior apophysis short and thin. Eighth tergite short and narrow, quadrangular; anterior apophysis thin, 2.5 times longer than posterior apophysis. Ostium bursae broad, V-shaped, caliciform; ductus bursae very short and narrow, lateral margins broadly sclerotized; cervix bursae membranous, unmodified, ductus seminalis moderately thick. Distal tubular part of corpus bursae long and relatively narrow, slightly dilated anteriorly; dilated proximal part of corpus bursae spherical, slightly rugose; signum bursae moderately long (ca. one-third of diameter of corpus bursae), anteriorly gradually dilated and rounded, elongate teardrop-shaped.

Etymology

The new genus is named in honour of the late Dr Allan Watson, a renowned specialist of Drepanidae and former curator of the Lepidoptera collections of NHMUK. He was the first to recognise and describe Thyatirid moths from the Afrotropical Region, introducing the genus Aethiopsestis . The desinence “- psestis ” has been widely used in thyatirine generic names.

Figures

Figures 1–8: adults. 1, Marplena designina, holotype, ♂, RSA (©NHMUK); 2, Ibidem, paratype, ♀, RSA (©NHMUK); 3, Ibidem, ♂, RSA (MFN); 4, Ibidem, ♀, RSA (MFN); 5, Watsonopsestis smithi sp. n. holotype, ♂, Tanzania (ANHRT); 6, Ibidem, paratype, ♂, Tanzania (RCAK); 7, Ibidem, paratype, ♀, (©NHMUK); 8, Ibidem, paratype, ♀, RSA (©NHMUK).

Figures 19–25. Male genitalia. 19, Marplena designina, holotype, gen. slide No. BM Thyatiridae 259 (©NHMUK); 20, Watsonopsestis smithi sp. n., holotype, gen. slide No. LG 5749 (ANHRT); 21, Ibidem, paratype, gen. slide No. LG 5630 (RCAK); 22, Aethiopsestis austrina, holotype, gen. slide No. BM Thyatiridae 196 (©NHMUK); 23, Ibidem, paratype, gen. slide No. BM Thyatiridae 1 (©NHMUK); 24, A. nebulosa, holotype, gen. slide No. BM Thyatiridae 3 (©NHMUK); 25, Ibidem, paratype, gen. slide No. BM Thyatiridae 38 (©NHMUK).

Figures 30–34. Female genitalia. 30, Marplena designina, paratype, gen. slide No. BM Thyatiridae 260 (©NHMUK); 31, Watsonopsestis smithi sp. n., paratype, gen. slide No. BM Thyatiridae 195 (©NHMUK); 32, Aethiopsestis austrina, paratype, gen. slide No. BM Thyatiridae 41 (©NHMUK); 33, A. nebulosa, paratype, gen. slide No. BM Thyatiridae 39 (©NHMUK); 34, A. mufindiae, gen. slide No. LG 5628 (ANHRT).