Rondotia melanoleuca Cao & Liu, 2024

Liu, Zhengyang & Cao, Xiwen, 2024, Rondotia melanoleuca sp. nov., a new wild-mulberry silkworm from China (Lepidoptera, Bombycidae), Nota Lepidopterologica 47, pp. 49-56 : 49

Rondotia melanoleuca Cao & Liu sp. nov.

Holotype [HT].

Imago, 1 ♂ ([unique identifier: A23072701]: China, Dafengding, Leshan, Sichuan Province, ca. 1500 m (Fig. 1A, B ). A red label “HOLOTYPE” will be added, and the holotype will be deposited at the Institute of Zoology, Chinese Academy of Sciences, Beijing.

Paratypes [PTs].

Imagines, 4 ♂♂ [unique identifiers: A23072702-A23072705] and 4 ♀♀ (unique identifiers: A23072706-A23072709] (e.g., Fig. 1C-H ), same data as for HT. All are preserved in the collection of the senior author (Beijing) with blue paratype labels.

Descriptions.

Mature Larvae (Fig. 2E, F ):

Morphology. Head capsule is dark gray and sparse yellow powder is visible in some individuals, with yellowish adfrontal area, and labrum and basal antacoriae a pale yellow. The integumentary color of T1-A10 is mostly vivid yellow, transversely decorated with black, dotted stripes. In lateral view, T2 is the most swollen area dorsally. Legs T1-3 are speckled with black on the lateral regions, while prolegs A3-6 have a yellow ground color similar to the former. Caudal horn on middorsal A8 is black and strongly developed.

Biology. A total of ten mature caterpillars were collected from a Morus sp. ( Moraceae ) in the wild at the type locality, on 02.v.2022. They were sent to Cao in Beijing and reared successfully in captivity on Morus alba . Liu had observed an individual on Camptotheca acuminata ( Nyssaceae ) at Fugong County, Yunnan, 1221 m, on 28.v.2023. After being brought back for indoor observations, it did not continue to feed on this plant or accept mulberry, and it ultimately starved to death. The caudal horn usually points to the posterosuperior side at rest, but it will swing back and forth (from anterior to posterior sides, with unstable frequency and speed) when frightened and crawling. After feeding ended, mature larvae always left their host plants to pupate in a cocoon. The larvae of HT and PTs span their cocoons ca. 05-09.v.2022.

Pupae (Fig. 2G, H ):

Morphology of male and female pupae. The exterior shell is translucent after sclerotization is completed, showing yellowish tissues inside. Melanin is primarily pigmenting the spiracles A2-8 of the pupal exuviae, then distributed internally around the spiracle T1, and also the areas of middorsal A1-7 and dorsolateral T1-3. The subterminal costal margins of forewings come in contact medioventrally; antennae, maxillae and legs T1-3 are clearly visible.

Biology. During development of the adult in the pupa, the proximal regions of antennae, of the lateral areas of compound eyes, off the tarsi of legs T1 and of the tip of A10 become pigmented blackish earlier than other structures.

Cocoons (Fig. 2G-I ):

Morphology. White ellipsoid in general, about twice as long as wide, with the pupa nested inside along its longitudinal axis. The outer fibers form a wrinkled, irregular layer, that appears as a loose and perforated filament-layer in horizontal section. The innermost [pupal chamber] surface of the cocoon is regular and relatively smooth.

Imagines (Figs 1 , 2A-D ):

Morphology of males. Head largely covered by black scales, but the frontoclypeal area is off-white, with black compound eyes and bipectinate antennae. The labial palpus is but vestigial and very minute. The white scales are distributed on the subdorsal areas T2-A8, the subventral areas A2-8 and the tip of A9. The abdominal venter is grayish, while other areas of the whole body bear black scales; especially on T1 and tegulae, these scales are longish and hair-like. Legs T1-3 are also darkly colored, and the longest hair-like scales are located on the lateral margins of tibiae and basitarsi of forelegs. Both fore- and hindwings are semitransparent, the lengths are ca. 2.2 cm (from the wing base to the tip of R4, HT) and ca. 1.8 cm, (from the wing base to the tip of CuA1, HT), respectively. Viewed from both dorsal and ventral sides, each wing-vein is located within a gray-black scaly stripe, such bands likewise decorated on the postbasal (only forewings), median (all wings), marginal (all wings, and here including costa-apex-termen-inners) areas, while other regions have a light cover with white scales. The termen of the hindwing is slightly concave around the tip of 1A.

The sternum A8 is caudally digitiform and directed toward the posterior side, carrying dorsolateral bristles. Amongst the genital structures, tegumen and vinculum are fused and form a narrowly elliptic ring, with the vinculum extending into a very short saccus. The uncus is deeply bilobed, laterally sclerotized and medially membranous, its wedge-shaped terminal is inferolaterally setose. A pair of cambered sclerites derived from the gnathos is strongly developed, linked with the uncus by lateral membrane. The narrow and crescent valva is expanding terminally which ended with a rounded and smooth dorsodistal margin, each cucullus has serrated inferior margin with two or three identifiable pointed teeth bearing medioventral corona. The juxta is V-shaped and slightly protruding. The phallus is thin, long and straight, with a pointed tip that has a slightly helical opening; the caecum penis is well developed.

Morphology of females. Color pattern is nearly identical to males,but females are usually larger in size than males. Visually, wings appear narrower, longer and paler than in males, with lengths of forewing ca. 2.4 cm (from the wing base to the tip of R4, PT [A23072706]) and hindwing ca. 1.9 cm, (from the wing base to the tip of CuA1, PT [A23072706]). Prior to oviposition, A2-7 medioventrally covered by many long, black scales.

Biology. Adults HT and PTs emerged from cocoons between 14 and 18.v.2022. In resting position, moths usually hold their forewings with their costal margins horizontal (perpendicular to the body), while the anal angles of the hindwings are widely separated from each other (Fig. 2D ). There was no successful pairing in captivity, but adults were found to be active during the day. Unfertile females nonetheless laid eggs, covering them with black scales from their abdominal midventral areas. It is noteworthy that the dorsal epicuticle of the membranous areas of wings appeared slightly iridescent while moths were alive, which was difficult to observe in dead, dry specimens.

Distribution.

The specimens in this study are all from Leshan (Sichuan) and Fugong (Yunnan), but the new species may be more widely distributed in montane broadleaf forests in both provinces. However, due to the presence of similar environments, we presume the species may also be found in the northern Indochina Peninsula, e.g., in Myanmar, Laos, and Vietnam.

Diagnosis.

Adults of R. melanoleuca sp. nov. have wings with distinct white patches placed between black vertical stripes and black wing-veins, which enables easy distinction from all other bombycids without dissection of genital structures. Wang et al. (2015) provided a diagnosis for R. menciana , R. diaphana and R. lineata , in which they noted "forewing with outer margin concave below apex and a projection at the end of M3 [ …] uncus divided into three lobes; valval apex broader with a large and a small tooth". In contrast, the new species has a straighter forewing termen, a biforked uncus, and a rounded dorsodistal edge of the valva.

Etymology.

This feminine adjective in modern Latin means "black and white"; interestingly, the Sichuanese giant panda carries the same specific name.

Molecular phylogeny.

The phylogenetic tree (Fig. 3 ) reveals that R. melanoleuca sp. nov. is sister to R. menciana + R. diaphana , with a high support value of 99%. The generic relationships revealed by the topology obtained are in agreement with Wang et al. (2018) and Deng et al. (2022).

Figures

Figure 1. R. melanoleuca sp. nov. A, B. HT: ♂ A. Dorsal view; B. Fore- and hindwings, ventral view; C, D. PT [A 23072706], ♀: C. Dorsal view; D. Fore- and hindwings, ventral view; E-H. PT [A 23072704], ♂: E. Sternum A 8, dorsal view; F. Phallus, lateral view; G, H. Main genital sclerites of A 9 - 10; G. Posterior view; H. Lateral view. Scale bar (left) for A-D: 1 cm; scale bar (right) for E-H: 1 mm.

Figure 2. R. melanoleuca sp. nov. A-E, G-I. Specimens from the type locality; F. Specimen from Fugong County, Yunnan. A. Adult ♂, newly emerged, dorsal view, front light photography; B, C. Adult ♀, newly emerged, surround light photography: B. Dorsal view; C. Ventral view; D. Adult ♂, natural resting condition, dorsolateral view; E. Mature larva, dorsolateral view; F. Mature larva, lateral view; G, H. Pupa ♀, within an opened cocoon: G. Lateral view; H. Ventral view; I. Cocoon, lateral view. Scale bars: 5 mm.

Figure 3. ML tree of the family Bombycidae (part) based on COI dataset, the outgroup (Saturniidae) is not shown. The scale bar indicates average substitutions per site. The nodal support is indicated by ultrafast bootstrap values.