42 Bulletin American Museum of Natural History [Vol. XLII 



Thoracic segments wider than the head. Folds and lobes of whole body much 

 more distinct than in other stages. Legs about five-sixths as long as the thorax is 

 wide. Abdomen spindle-shaped. 



Pupa. — Length, 24 mm. with cerci (curled up); width at its thorax, 14.5 mm. 

 Whitish. Head smooth, only one small posterior supraorbital stylus noted; two 

 small, oval, raised areas on each side of the epicranial suture near the vertex. Pro- 

 notum smooth, its cephalic margin concave. Styli arranged as follows: three long 

 styli, curving backwards, in a transverse row at the anterior margin on each side; 

 eight shorter ones near the posterior margin, besides two very small ones just inside 

 the inner two styli; a few other scattered ones. Mesonotum and metanotum with a 

 pair of styli in a transverse row. Scutellum well marked. Metasternal spine long. 

 Inner spur of metatibiae very prominent. Metathoracic legs long nearly attaining 

 the end of the body. Tarsi not ending in prominent spines nor tibiae spinous on the 

 outer side. Metathoracic pterothecee visible from above. First to seventh ab- 

 dominal tergites with a transverse row of four styli, the outer one on each side mounted 

 on a tubercle. The styli just behind the spiracles longer than the others and curved 

 backwards. Second to seventh pleurites each with a stylus. Eighth abdominal tergite 

 with two small rounded tubercles at the posterior margin on each side of the median 

 line and each bearing a short terminal stylus. Ninth abdominal segment terminating 

 in two superficially annulate cerci about 2.5 mm. in length and with a prominent 

 short, ventral spine between their bases. Abdominal spiracles oval, uncovered and 

 prominent (second to sixth visible). 



8. Hydrobiinae 



Eggs usually enclosed in a silken case with a prominent projection but some- 

 times laid in a mass with a loosely applied covering of silk (Cymbiodyta and Para- 

 cymus) or held on the under side of the body by the elytra (Epimetopus, Choetarthria ?) 

 or hind legs (Helochares). 



Larva with head elevated. Antennae with points of insertion situated farther 

 from the externo-frontal angles than those of the mandibles; second segment with 

 an antennal appendage. With or without an epicranial suture; ocular areas flat, 

 elongate, in groups of six, closely aggregated; labrum and clypeus both reduced and 

 united, the anterior margin more or less toothed; mandibles prominent, sharply 

 pointed and with inner teeth; maxillae palpiform and stipes with a rudimentary inner 

 lobe. Labial palpi longer than in other subfamilies; the second segment distinctly 

 longer than the first. Ligula present except in Berosus and Laccobius; labium and 

 maxillae inserted at the front margin of the under side of the head 1 and not attaining 

 the occipital opening. Eight complete abdominal segments and a rudimentary ninth 

 and tenth ; the chitinization is entirely lacking, except the dorsal plate of the eighth 

 segment and chitinized patches on the praescuta. Cerci two-segmented but reduce 1 

 (absent in Berosus). Type of breathing is pseudo-metapneustic except in Berosus, 

 which possesses tracheal gills and a rudimentary stigmatic atrium. All genera have 

 poorly developed bifore spiracles. 



Vestiges of furrowed condition in Berosus and Laccobius, 



