CALIFOKXIA ACADE>[Y OF SCTEXCES. 3 



bust in Metaxyodonta — and scarcely perceptibly incrassate. 

 The riftli abdominal segment is almost invariably ccpial in 

 length to the tliird and fonrth together. Tlie labrum differs 

 thronghout, and is, in conjunction with the relative length 

 of the first joint of the posterior tarsi, made the principal 

 basis of generic snbdivision. It is singular, however, and 

 a strong proof of the validity of the genera, that these two 

 fundamental characters are accompanied by other very rad- 

 ical differences in many of the most important parts (^f the 

 body, as well as in completely radical differences in the na- 

 ture of the male sexual modifications; these are described in 

 tbe table of genera given below. 



The genera Stilicus, Scop;eus, Orus, etc., should pre- 

 cede those here given in a systematic arrangement of the 

 Paederi, and are distinguished from them by theii- very 

 strongly dilated tliird maxillary palpal joint. 



San Fraucisco, Jan. 1st, 18i6. 



Note 1. — Iq estimating the order of the abdomiual segments in the foHow- 

 ing pages, the numbers refer to visible segments only. 



Note 2.— Separate diaguoses of the various species are not given at present, 

 as this paper is simply intended as the forerunner of a more general one upon 

 our Pioderini. 



(iEXERIC DEFINITIONS. 



Head slightly narrower than the prothorax, sides parallel; e\'es moderate 

 in size; labrum 4-deutate, the teeth being rather prominent, acute and nearly 

 equi-distaut. Trothorax quadrate; sides parallel or veiy slightly narrowed 

 from apex to base. Elytra much longer than the prothorax. First joint of 

 the posterior tarsi as long as the next two together, or nearly so. Male sex- 

 ual characters very simple; fifth segment not modified, sixth narrow, with a 

 small Him])le sinuation at the apex Genus Caloderma 



Pronotum longitudinally rugulose Species I — ;{. 



Prouotnm finely and generally very densely punctate Species -1 — «. 



Head rather large, slightly wider than the prothorax; eyes very small; la- 

 brum with a very small deep median emargiuatiou, slightly wider than deep, 

 immediately adjoining which there are on each side two approximate and ex- 

 ceedingly minute acute teeth. Prothorax with the sid^s convergent pos- 



