NORTH AMERICAN COLEOPTERA. ^ 69 



Antenn.e. — These difter in form and color. 



Form. — The only instance of variation of form occurs in group 

 viii, in which the only known male has the lower edge doubly serrate 

 (fig. 238). In the females of this group the lower edge of the an- 

 tennae is broader than in the species of the preceding series. 



Color. — The most common difference is that the male antennae 

 are brighter in color, green or cupreous, while in the female they are 

 bronze or piceous. In acutipennis joints four to eleven of the male 

 antennae are more or less testaceous, in the $ bronze. 



Prosternum. — It is quite common to find the same differences in 

 the prosternum as have been observed in the front, that is, more 

 densely punctured and finely pubescent % , or more coarsely and 

 sparsely punctured and less pubescent 9 . It is, however, not rarely 

 that both sexes are similar and have coarse, sj^arse punctuation, or 

 the prosternum may be very nearly smooth. 



Legs. — The femora show no perceptible differences in the two 

 sexes, except that in the males they are slightly stouter. The tooth 

 is similar. 



Tihixe. — The differences between the two sexes is usually very 

 well marked. In the female the tibia is at most feebly arcuate 

 without apical dilatation or tooth or serration on the inner edge. In 

 two species, aziirea (221) and atrifaseiata (242), the tibiae are so nearly 

 alike in the sexes that the difierences might readily escape observa- 

 tion, and in libonoti (197) they do not differ at all. In the males 

 the anterior tibiae are always more or less arcuate, and in one 

 species impressa (202) angularly bent. A comparatively small num- 

 ber of species have the anterior tibiae serrulate on the inner margin, 

 and in these it will be observed that the aj^ical dilatation is either 

 feeble or null. Those with the tooth at a greater or less distance 

 below the middle are even less numerous. The apical dilatation is 

 of very variable form and size, as will be seen on the accompanying 

 sketches. The middle tibiae show much less variation, but in floricola 

 (50) they are distinctly sinuate, in a few other species the tip is 

 slightly thickened, while in femorata and Merkelii they are nearly as 

 serrulate as the anterior tibiae. In a large number the middle tibia 

 S is arcuate, but much less than the anterior, while in the $ it is 

 usually straight. In but one species, scabripennis, the posterior tibia 

 % is arcuate. 



