Rhipidolestidae, Silsby, 2001

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 : 237-238

Family Rhipidolestidae

Only larvae of the genus Rhipidolestes are known ( Fig. 16 ), from three species from southern Japanese islands and Taiwan (Tabaru 1975, Asahina 1994, Ishida 1996). Working in a small forested mountain stream in Kumamoto Prefecture, Kyushu, Tabaru (1975) determined that R. aculeatus Ris (a species also present in Taiwan) completes 13 larval stadia with a three–four year developmental period. He observed: “The larvae are active but they seem to be nocturnal insect[s] taking small aquatic animals in the water. They avoid the1ight and hide themselves in the daytime under the bryophytes or among the plant leaves. They feign death...” The habitus of every instar is depicted photographically, but no detailed description is provided (although a later morphological description of the F larva is promised, but evidently did not eventuate).

The genus includes at least 23 species (undescribed species are illustrated in Zhang 2019), a majority of which occur in the Oriental realm, but a significant number of which are confined to the Sino-Japanese realm; the exact numbers are difficult to establish owing to a lack of clarity in the northern boundary of the Oriental realm defined by Holt et al. (2013). Elsewhere in the Oriental realm the genus ranges from northern Myanmar and Indo-China to Southern China where the adults are found around small slow flowing shady forest streams and seepages from low altitudes to about 2000m, with species showing differing altitudinal preferences ( Zhang 2019). The larval habitat is generally expected to be near the adult haunts. The larvae bear a superficial resemblance to those of Euphaeidae , especially Bayadera but are smaller and are immediately recognised by the lack of ventral abdominal gills. The antennae are relatively short and stout, especially in the basal segments. The prementum is broad and short with a moderately produced, rounded anterior median lobe with a moderately developed median cleft; the labial palps are short ( Fig. 17 ). As Bybee et al. (2021) were not fully confident in the composition of the family it is possible the as yet unknown larvae of other genera differ significantly.

Unknown larvae: Agriomorpha (2 spp.), Burmargiolestes (2 spp.), Bornargiolestes (3 spp.)

Figures

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).