H. C. FALL 303 



degree of slenderness of the organ. Other details would be of 

 little use and largely a matter of repetition. 



Prothorax. — The form of the prothorax varies somewhat but 

 is not of much use in the separation of species. It is more or 

 less wider than long in all species, and is nearly always distinctly 

 widened posteriorly, but in a few species, e. g., quadratus, the 

 base is scarcely wider than the apex. There is a definite basic 

 color scheme which will be alluded to below, and it may be said 

 here as of the head, that the darker areas arc more closely punc- 

 tate. The density and coarseness of punctuation naturally 

 varies consideraljly in so large a genus, but in only one respect 

 have I found it signally useful in tabulating the species. In a 

 large majority of species the punctuation becomes distinctly 

 sparser or almost disappears along the side margins, ))ut in quite 

 a number of forms the surface is nearly equally densely punctured 

 to the extreme margins. 



Elytra. — The only important characters drawn from tlie elytra 

 aside from the markings are those of punctuation. In the most 

 completely striate forms, of which pdUidipennis is the best 

 example, there are a sutural, marginal and eight discal striae on 

 each elytron. The sutural stria diverges oljliquely from the 

 suture anteriorly and within it in the scutellar region arc one or 

 two short lines of punctures which are, however, in most species 

 quite irregular or completely confused. In the following descrip- 

 tions the discal striae only are nundDcred, that next to the sutural 

 being called the first, and the one next within the marginal the 

 eighth or submarginal stria. From the completely striate paUidi- 

 pennis to the entirely confusedly punctate microps there is every 

 intermediate stage of regularity or irregularity of strial develop- 

 ment. In the vast majority of species the striae are, in part at 

 least, more or less obvious, the eighth being most persistent, while 

 fragments at least of some of the others are visible on the decliv- 

 ity. The first discal stiia diverges from the suture anteriorly 

 as does the sutural one, and both arc often lost in the confused 

 punctuation of what I have called the baso-sutural region or 

 triangle. In very many species the first stria suffers either a 

 gradual or an abrupt displacement toward the suture, at or al)Out 

 the middle of the elytra, enclosing between it and th(> second 

 stria at this point a small area which Mr. Bowditch has called the 



TKAXS. AM. KN'T. SOC, XLI. 



