Vestalis, 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 : 227

Vestalis

With 16 species occurring from Yunnan, southernmost China, the Philippines and Bali in the east to the western Ghats and Sri-Lanka in the south-west the genus is the most speciose and diverse of the family in the Oriental region. The first description of a larva was Vestalis luctuosa (Burmeister) from Java by Ris (1912), who provided diagnostic drawings of exquisite detail, including the tiny supplementary antennomere following the pedicel ( Fig. 36a ), noted with approbation by Lieftinck (1965), who illustrated the habitus. Lieftinck (1965), also described a larva of the V. amoena Hagen group, with the species not identified with certainty. Lieftinck notes that the median caudal gill of the amoena group is truncated ( Fig. 50 ) whereas in luctuosa it is acuminate ( Fig. 51 ). In particular he states “A peculiar feature of the antennae... [of all Vestalis ] is the presence of a vestigial—rarely incompletely developed—extra joint between the pedicel and the second segment [a lapsus, he means pedicel and scape, since the pedicel normally is the second segment]. This intercalated minute segment is present in all [ amoena ] individuals examined...”. However, in another lapsus, his illustration ( Fig. 13c in Lieftinck 1965) of the antenna shows no trace of this vestigial segment, leading later authors ( Rattanachan et al. 2022) to state incorrectly that V. amoena lacks the supplementary third antennomere. I have examined specimens of V. amoena , V. amaryllis Lieftinck (supposition), and V. amnicola Lieftinck , from Brunei ( Orr 2001, Orr unpublished data), all belonging to the V. amoena group, and all have the supplementary third antennomere and in consequent 8 segments in total. Lieftinck (1965) also notes how in general build Vestalis larvae are intermediate between the spidery long legged Neurobasis and the stouter Echo larvae. Larvae of the V. amoena group are variously found depending on their habits “among leafy trash in a shady brook”, ( Lieftinck 1965), to the underside of stones at the edge of a fast-flowing stream and leaf packs among riffles ( Orr 2001). It seems likely that the sylvan V. beryllae Laidlaw breeds in boggy springs among leaf litter as the adults are always to be found in such places ( Orr 2001). Other descriptions and illustrations of Vestalis larvae include: V. amoena group, photograph of habitus; V. gracilis (Rambur) , description and illustrations of diagnostic structures and habitus with note “usually concealed among vegetation in riffle zones”, ( Rattanachan et al. 2022); V. melania Selys , description and illustrations of diagnostic structures and habitus ( Fig. 53 ) with note “found in an unshaded, narrow, montane stream with a sandy substrate and dense marginal and submerged vegetation”, as well as comparisons with other species ( Guadalquiver et al. 2022); V. nigrescens Fraser , stated by St Quentin (1973) to be similar to V. luctuosa , with acuminate caudal lamellae, and inhabiting the banks of stony bottomed streams.

The species, essentially alike in general appearance, fall into two categories: those with a truncate median caudal gill ( Fig. 50 ), ( amoena group and gracilis ) and those with an acuminate central caudal gill ( Fig. 51 ), ( luctuosa , melania and nigrescens ). There are also differences in the shape of the mask, which tends to be relatively broader apically with shorter, broader premental lobes in luctuosa and perhaps melania and with subtle differences in the form of the premental cleft, about which Lieftinck (1965), who first noted a possible difference, remained sceptical. With good information available for fewer than half the known species, morphology based larval identification will generally depend on locality, with the probability that eight antennomeres with a tiny third segment is positive proof of generic identity.

Figures

FIGURES 35–41. 35. Archineura incarnata, prementum (dorsal view, drawn from Yang et al. 2022). 36. Vestalis gracilis, prementum (dorsal view) and right antenna with supplementary antennomere between pedicel and scape (a) arrowed (redrawn from Rattanachan et al. 2022). 37. Vestalaria venusta: prementum (dorsal view) and right antenna (drawn from Wang et al. 2017). 38. Caliphaea angka: prementum (dorsal view) and right antenna (drawn from Yang et al. 2021). 39. Heliocypha biseriata, frontal view of labrum showing dorsal and ventral sections and ‘moustache’ of long, heavy setae on the latter (from Orr et al. 2024). 40. Heliocypha biseriata: details of labial palp in relation to prementum (a) dorsal view—base of movable hook dashed to reveal palpal lobe beneath and open base of premental median cleft arrowed, (b) frontal view, (c) inner view (from Orr et al. 2024). 41. Heliocypha biseriata, detail of fore tarsus with pectinate setae magnified (from Orr et al. 2024).

FIGURES 42–51. 42. Archineura incarnata: caudal gills; left lateral above, median below (drawn from Yang et al. 2022). 43. Echo modesta: caudal gills; left lateral above, median below, with baso-dorsal shield arrowed (original illustration). 44. Psolodesmus mandarinus, dorsal view of caudal gills, with baso-dorsal shield of median gill arrowed (redrawn from Matsuki & Lien 1978). 45. Mnais andersoni, left lateral caudal gill with upper margin of median gill visible; baso-dorsal shield of median gill arrowed (original illustration). 46. Mnais gregoryi: caudal gills; left lateral above, median below, with baso-dorsal shield arrowed (drawn from Yang et al. 2021). 47. Caliphaea angka: caudal gills; left lateral above, median below (drawn from Yang et al. 2021). 48. Matrona basilaris: caudal gills; left lateral above, median below (drawn from Wang et al. 2017). 49. Vestalaria venusta: caudal gills; left lateral above, median below (drawn from Wang et al. 2017). 50. Vestalis amoena group: caudal gills; left lateral above, median below (redrawn from Lieftinck 1965). 51. Vestalis melania: caudal gills; left lateral above, median below (redrawn from Guadalquiver et al. 2022).

FIGURES 12–17. 12. Mesopodagrion tibetanum, habitus with detail of right profile of head (based on Yu 2016). 13. M. tibetanum, detail of mask (redrawn from Yu 2016). 14. Podolestes orientalis, habitus (from Choong & Orr 2010). 15. Podolestes orientalis, detail of mask (from Choong & Orr 2010). 16. Rhipidolestes aculeatus, habitus and detail of lateral and median gill (modified from Asahina 1994). 17. Rhipidolestes aculeatus, detail of mask (modified from Ishida 1996).

FIGURES 52–56. 52. Caliphaea angka, habitus (based on Yang et al. 2021). 53. Vestalis gracilis, habitus (redrawn from Rattanachan et al. 2022). 54. Neurobasis chinensis, habitus (original drawing). 55. Matrona basilaris, habitus (drawn from Wang et al. 2017). 56. Echo uniformis, habitus (redrawn from Lieftinck 1965).