100 Proceedings of the Biological Society of Washington. 



tions noted in the 'Classification." To what extent it is 

 proper to ignore or use for classification, characters developed 

 by a species and by which it has adapted itself to a peculiar 

 mode of life is a matter for much thought. Often the most 

 obviously distinct characters are of recent development and 

 trifling importance. 



The family may, however, be temporarily characterized as 

 follows: 



Adults of small size, sexes similar, elongate, slender, depressed, feebly 

 chitinized. Facies of a small Hydnocera. Head horizontal, wider than 

 pronotum, narrower than humeri; eyes sub-globular, prominent; antennae 

 widely separated, short, 11-jointed; joints 1 and 2 large, sub-globular; 

 3d and 4th small, globular; 5th t<> loth gradually increasing in width 

 and becoming transverse ; 11th elongate 4 , oval; mandibles strong, promi- 

 nent, tridentate; maxillary palpi simple in both sexes, 4 jointed, last 

 joint almost as long as preceding three; gula wide, indistinctly margined 

 by externally arcuate lateral sutures. Prothorax shorter than head, side 

 margins obsolete; presternum not limited laterally, but transversely 

 convex to dorsum, front margin straight, hind margin feebly arcuate 

 between coxae which are open and contiguous; metasternum comprising 

 about one-third the length of the body. Abdomen composed of 6 free 

 ventral segments in the $ , 7 in the d\ of which the last is short and 

 narrow. \a^ short, tibiae with rather strong spine, 5th tarsal joint 

 only a little shorter than the four preceding. 



Male. — Antennae narrower, ventral abdominal segments :!, 4 and 5 

 with large median gland pore out of which project numerous hairs. 



Female.— Antennal joints 5-11 wider; ventral abdominal segments 1 

 and 2, feebly chitinized; two anal processes acute, divergent and pointing 

 downwards. 



The writer hopes to give a complete account of the extraor- 

 dinary life-history of this beetle at a later date. 



