Bayadera, Selys, 1853

Orr, Albert G. W., 2024, A review of present knowledge of larvae of the Calopterygoidea (Zygoptera) of the Oriental realm, including keys to families and known genera, Zootaxa 5497 (2), pp. 209-243 : 233-234

Bayadera

The genus presently includes 17 species ranging from Himachal Pradesh ( India) in the Western Himalayan region, through Northern Myanmar, Thailand, Indochina, mainland China, Hainan and Taiwan. In mainland China Bayadera melanopteryx ranges north into the Sino-Japanese realm of Holt et al. (2013), formerly included in the Palaearctic realm. The larvae of more species have been described than other most euphaeid genera and there is clearly significant intrageneric variation in several characters, although the quality of illustrations and descriptions leave some uncertainty regarding diagnostic details, particularly the form of the caudal gills. Keetapithchayakul et al. (2020) analysed differences in larvae of species then known.

The larva of B. indica Selys from the Himalayas was first mentioned by Hagen (1880) as Anisopleura comes ? (see Needham 1911) who described the caudal gills as conical and short and noted that the second antennomere was shorter than the third. The same species was described and figured accurately and in some detail by Needham (1911), information partly repeated in Needham (1930). Evidently unaware of this work, Fraser (1934) stated incorrectly that the larva was unknown for the genus, which is the more curious as earlier he had ( Fraser 1929b) asserted (incorrectly) that Bayadera larvae lacked abdominal gills. The larva of B. indica was also figured in detail by Kumar (1973), with structural details well presented and generally agreeing with Needham (1911). However Kumar (1973) depicts the habitus rather roughly, with a longer filament on a caudal gills reminiscent of Anisopleura or Euphaea and inconsistent with Needham’s (1911) detailed drawing of the lateral gill and also the habitus drawing seems to show the antennae too short for Bayadera , whereas in the detail of the head they are longer.

Matsuki & Lien (1978) described and illustrated the larva of B. brevicauda Fraser from Taiwan, showing very squared caudal gills with a short narrow tip constricted at the base, which they describe as “more or less sausage shaped with a short tail”. Ishida (1996) figured B. ishigakiana Asahina in detail, illustrating a rather attenuated tip to the gills, which arise abruptly and do not taper from the main sac as in other species of the genus, although this form, while similar is less extreme in an illustration by Sugimura et al. (1999). Wan et al. (2011) describe and figure diagnostic details for B. bidentata Needham ; The caudal gills are depicted as sausage shaped and tipped with a short, abrupt cone, and a similar form was found in B. serrata Davies & Yang by Keetapithchayakul et al. (2020) and in B. strigata Davies & Yang ( Fig. 68 ) by Yang & Orr (2024).

Larvae of Bayadera tend to be slighter in build than Euphaea , with longer legs ( Fig. 58 ), and the hind margin of the head is slightly more rounded, but these differences cannot be considered diagnostic. All species known share the following characteristics: the antennae are conspicuously long, being longer than the distance between the posterior occipital margin and the base of the labrum. The postocular lobes are strongly developed, slightly bulbous, and smoothly rounded ( Fig. 64 ). In species for which information is available ( B. indica , B. serrata , B. strigata ) the male genital apophyses are large and rounded, curving to overlap S10 ( Fig. 71 ), in which respect they differ from Euphaea . There are few or no tubercles on the labrum and anterior part of the head, as in Anisopleura and claviform setae characteristic of all euphaids are often especially dense in this area. The inner apical process of the labial palp is free and securiform except in B. bidentata in which it is almost atrophied to an angulated thorn like process, but also supplemented by another blunt process about the mid-inner margin of the palp that is unknown in any other member of the family. In species examined sufficiently closely ( B. indica , B. serrata , B. strigata ) the outer apical process of the lobe of the labial palp has a wavy margin unknown in other described genera ( Fig. 66 ).

Most species lack long spines on the genae (longer than about one third of the width of the ventrally visible compound eye), but B. serrata has 1–3 spines Keetapithchayakul et al. (2020), hence a lack of spines or just one spine generally indicates that the larva is Bayadera , but presence of multiple spines does not rule out the genus.

Bayadera larvae are typically found clinging under stones in clear, moderately fast flowing water in shallow streams. At higher altitudes they frequently occur together with Anisopleura larvae, apparently in very similar microhabitats. The various species have different altitudinal preferences ranging from 500–2500m ( Zhang 2019) . Rasaily et al. (2021) report Bayadera larva at many locations in Bhutan, some quite disturbed, from ca 500– 1300m .

Figures

FIGURES 67–74. 67. Anisopleura subplatystyla, caudal gills dorsal view (original drawing). 68. Bayadera strigata, caudal gills dorsal view, (drawn from Yang & Orr 2024). 69. Euphaea decorata, caudal gills dorsal view (drawn from Xu 2017). 70. Euphaea superba, caudal gills dorsal view (redrawn from Wu et al. 2017). 71. Bayadera strigata: male genital apophyses; ventral (left), right lateral (right), (drawn from Yang & Orr 2024). 72. Euphaea decorata, male genital apophyses; ventral view (drawn from Xu 2017). 73. Euphaea superba, terminal processes of palpal lobe ventral view (movable hook truncated), (redrawn from Wu et al. 2017). 74. Anisopleura furcata, left labial palp showing terminal processes of palpal lobe, dorsal view (redrawn from Keetapithchayakul et al. 2024).

FIGURES 57–60. 57. Dysphaea gloriosa, habitus (drawn from Nguyen et al. 2024). 58. Bayadera strigata, habitus (drawn from Yang & Orr 2024). 59. Euphaea decorata, habitus. (drawn from Xu 2017). 60. Anisopleura furcata, habitus (drawn from Keetapithchayakul et al. 2024).

FIGURES 61–66. 61. Dysphaea gloriosa: detail of spines on genae and postocular lobe; underside (left), upperside (right) (modified from Nguyen et al. 2024). 62. Heterophaea barbata: dorsal view of head, showing (a) outer mandibular spines (b) genal spines partially visible and (c) right antenna (from Orr & Hämäläinen 2024). 63. Anisopleura subplatystyla, dorsal view of head (original drawing). 64. Bayadera strigata, dorsal view of head (drawn from Yang & Orr 2024). 65. Euphaea decorata, dorsal view of head. (drawn from Xu 2017). 66. Bayadera strigata, left labial palp with detail showing wavy outer margin of outer process of palpal lobe (arrowed), (drawn from Yang & Orr 2024).