Philogangidae, Kennedy, 1920

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 : 236

Family Philogangidae

The single genus Philoganga is known from four large species ranging from the eastern Himalaya, northern Myanmar, Thailand and Indochina to southern China. The larvae of three species are known, and are generally similar, Fraser (1938) described and figured P. montana (Hagen) , Chao (1948, 1953) discussed Chinese species, including P. robusta Navás , and the most detailed descriptions are available for P. vetusta Ris ( Asahina 1967, Xu 2016, Ng 2024e). The larvae ( Fig. 24 ) are found among stones in clear wooded streams in hill country up to 1200m. Fraser (1938) reported P. montana as inhabiting “...torrential mountain streams, clinging to the underside of stones or rocks or hiding up in clefts of rocks.”. Mature larvae are easily distinguished by their massive head, eight segmented antennae ( Fig. 25 ), (although Asahina (1967) reported some specimens of P. vetusta with only seven antennal segments), long tapered saccoid terminal gills and large size. As far as is known all species bear a cluster of long strong subocular spines on the anterior gena; the prementum ( Fig. 26 ) is broad, with rounded lateral margins bearing short spines in their anterior half, a slightly produced anterior median lobe with short median cleft. I was able to make direct comparisons with an exuvia of P. montana collected in Nepal by S.G. Butler (see Kemp & Butler 2001), which had 8-segmented antennae, and, aside from its huge size (total length excluding antennae and caudal gills 40mm) it differed only slightly from the allopatric P. vetusta .

Figures

FIGURES 18–26. 18. Rhinagrion borneense, habitus (original drawing). 19. Philosina alba, habitus (modified from Zhang et al. 2011). 20. Rhinagrion mima, caudal gills: above heavily tracheated median gill; below right lateral gill with basal spines along mid-rib (modified from Lieftinck 1956). 21. Philosina alba caudal gills: above heavily tracheated median gill; below right lateral gill with basal spines along mid-rib (modified from Zhang et al. 2011) 22. Rhinagrion borneense, detail of mask (original drawing). 23. Philosina buchi, detail of mask (redrawn from Zhang et al. 2011). 24. Philoganga vetusta, habitus (adapted from Xu 2016). 25. Philoganga vetusta, details of caudal gills and antenna (redrawn from Xu 2016). 26. Philoganga montana, detail of mask (original drawing).