94 Bulletin American Mvseum of Natural H ml ory | Vol. XL11 



Plate I 



Fig. 1. Labium, ventral view. Hydrophilus oblusatus larva. 



Fig. 2. Head without appendages, dorsal view. 



Fig. 3. Egg-case. Hydrobius fuscipes. 



Fig. 4. Mandible of primitive larva of Ochthebius type. 



Fig. 5. Maxilla of specialized type of Hydrophilid larva. 



Fig. 6. Caudal view of open stigmatic atrium. Hydrophilus oblusatus. 



Fig. 7. Side view of last three segment of larva. Hydrous triangularis. 



Fig. 8. Side view of caudal end of larva with anus protruded. Hydrobius 

 fuscipes. 



Fig. 9. Dorsal view of closed stigmatic atrium of larva. Philydrus nebulosus. 



Explanation of Lettering on Plate I. ' Numbers Refer to the Abdominal Seg- 

 ments. 



a, anus; ab, abductor muscle; ac, acrocerous; ad, adductor muscle; ai, antennal insertion; ap, 

 anterior piece of mandible; c, condyle; ca, cardo; cp, cap of egg- case; e, lateral expansion of epistoma; 

 ep, egg-case proper; e.s, epicranial suture; /, frons; fa.s, frontal antennal suture; fe.s, fronto-epistomal 

 suture; fl, filament of egg-case; g, gula; I, ligula; lb.pl, labial palpus; l.cl. labro-clypeus; 11, lateral 

 lobe; lm, lacinia mobilis; m, mentum; ma, molar area; mc, mesocercus (true cercus); ml, median 

 lobe; rnx.pl, maxillary palpus; on, ocular area; oc, occipital opening; pc, procercus or procerss of eighth 

 pleurite; plf, palpifer; plf.l, lobe of palpifer; pig, palpiger; pp, posterior piece of mandible; sc, sense- 

 cones; sm, submentum; st, stipes, (, troehantin; tr, trachea. 



