Philosinidae, Kennedy, 1925

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

Family Philosinidae

This small family ranges from southern China to Indochina, Thailand and much of Sundaland. The larvae of both genera are described ( Needham & Gyger 1939, Lieftinck 1956, Orr 2003, Zhang et al. 2011, Kawashima et al. 2011, Novelo-Gutiérrez et al. 2014), with both species of Philosina , P. alba Wilson and P. buchi Ris , and five of 10 species of Rhinagrion known. Not much interspecific variation is expected in the latter. Distinctive features of the family include: prementum with strongly developed median lobe with deep, apically closed, median cleft ( Figs 22, 23 ); median caudal gill densely tracheated, slightly ( Fig. 20 ) or significantly shorter ( Fig. 21 ) and thinner than the lateral caudal lamellae; lateral lamellae fleshy and undulating each with basally expanded midrib armed with spines on outer face. In Rhinagrion , in life the lateral gills form a tube shielding the median lamellae ( Kalkman et al. 2010) and it is believed the same may be true of Philosina ( Zhang et al. 2011) . The same authors claimed that Rhinagrion lack a subocular comb on the gena, present in Philosina , but this was shown to be incorrect by Novelo-Gutiérrez et al. (2014) in R. mima (Karsch) and a comb is also present in R. borneense (Selys) , (Orr, unpublished data). The only consistent differences between the genera appears to be relative leg-length, and the lateral caudal gills are relatively longer in Philosina and distinctly longer than the median one ( Figs 19, 21 ), whereas the median gill is only slightly shorter than the laterals in Rhinagrion ( Figs 18, 20 ). Also, in Philosina there are three variably developed setae on the anterior labial palp ( Fig. 23 ), whereas in published accounts of Rhinagrion , there is only one, but in R. borneense ( Fig. 22 ) there are two strong setae (Orr, unpublished data) hence this character is considered unreliable.

Key to genera

1 Legs very long; hind femur reaching abdominal S8–9; lateral caudal gill ovoid elongate, exceeding half length of abdomen; median caudal gill significantly shorter than lateral gills ( Figs 19, 21 ). Total length excluding caudal gills 14–20 mm ................................................................................................... Philosina [southern China and northern Indochina]

1’ Legs relatively shorter; hind femur reaching abdominal S6; lateral caudal gill squarish, nor exceeding half length of abdomen; median caudal gill slightly shorter than lateral gills ( Figs 18, 20 ). Total length excluding gills 12–14 mm ....... Rhinagrion [Southern China to Thailand and most of Sundaland]

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).