134 
NEUBOPTERA. 
while rare, are not unknown. A description of an aquatic Gryllid (Hy~ 
dropedeticus vitiensis Mial. and Gil.) will be found in Trans. Ent. Soc., 
Lond., 1902, p. 281. Tridactylus is found on the surface of water but 
usually lives on mud. (See p. 99.) Annandale has found an aquatic 
Blatta in Malaya and an aquatic Epilampra in India (Journ. Asiatic 
Soc., Bengal, 1906, p. 105). In India, one genus at least of Tetriginae 
(.Scelimena) is aquatic and an Acridiid allied to Hieroglyphus has the 
habit of diving below the surface. 
Amongst Neuroptera , there are several important groups. The 
Perlidce (Stone Flies) have aquatic nymphs, which have ten pairs 
of closed stigmata, and functional gills as a rule. A few are stated to 
have no gills but to have special tracheal developments at the skin. 
Others have gills on the first thoracic segment ( Nemoura , Pteronarcys) 
on the sides of the thorax ( Perla, Pteronarcys, Nemoura), on the apex of 
the abdomen (Perla, Pteronarcys) or on the head (Dictyopteryx signata). 
The Odonata are wholly aquatic with two modifications ; the Calyptery- 
gidce have leaf-like processes functioning as tracheal gills, the Aeschnidce 
and Libellulidce, rectal gills with anal valves to admit water, the 
gills in the former being papilliform, in the latter lamelliform. The 
Ephemeridoe are also aquatic with gills in the older stages. Lubbock 
has remarked that the skin of Chloeon functions till the third instar, 
when gills appear, but the tracheae are functional only in the fourth 
instar (there are 20 instars). Gills take several forms, and may be 
large and exposed, flat lateral plates, tubular under a gill cover, or 
concealed. The long caudal setae have a circulation and are probably 
also respiratory. Of the Sialidoe, the Sialince live in mud, the first 
seven abdominal segments having filaments functioning as gills. Of 
the Hemerobiidce, the Hemerobiince contain two aquatic forms, Osmylus 
and Sisyra, the latter with abdominal tracheal processes. The Trichop - 
ter a are wholly aquatic in the larval stage, having no gills (some 
Hydropsy chides, Rhyacophilides, Hydroptilides), or having gills in the 
form of tufts or slender processes, which may be placed all round the 
body. 
The Hymenoptera include a few remarkable parasitic forms which 
deposit their ova in the larvae of Trichoptera or other aquatic insects. 
Prestwichia in Europe is parasitic in the eggs of six species of aquatic 
insects. 
The Coleoptera include eleven families aquatic wholly or in part at 
least in their larval stages. Amphizoidce are metapneustic as larvae. 
The Pelobiidce are represented by Pelobius whose larva is said to have 
spiracles and blood gills. The larval Haliplidce have long filaments on 
the abdominal segments. Dytiscidce are wholly aquatic, the larva 
metapneustic, the imago carrying air under the wings. Gyrinidce live 
on the surface of the water as adults, but the larvae are provided with 
ten pairs of abdominal tracheal processes. The Hydrophilidce are only 
in part aquatic ; their larvae are either metapneustic or have tracheal 
