212 GEO. H. HORN, M. D. 



At this time it is as well to note the fact that the spurs of the female 

 hind tibipe are always movable, and there are always two spurs, 

 while in some of the males of the second series above indicated the 

 fixed spur may be very short or entirely absent, as in prununcuUna, 

 etc. (fig. 16) 



From the fact that the arrangement of the species is based almost 

 entirely on sexual peculiarities of the male, it is proposed to pass in 

 review the various members of the body and give, as briefly as pos- 

 sible, the modifications whether sexual or otherwise. 



Body. — The form is usually more robust in the female, more ex- 

 panded posteriorly and more convex, and when there are differences 

 in color the female is nearly always darker. 



Vestiture. — When the surface is hairy the pubescence is denser 

 and coarser in the female, the erect hairs, if any, are longer (see 

 Group XII). The metasternum is nearly always hairy, often densely, 

 the hair often long, but in nearly every instance the hair of the female 

 is shorter and less dense. 



Head. — In a number of species in various parts of the genus the 

 head is notably broad, with rather large and })rominent eyes. In 

 this case the head of the male is perceptibly the lai'ger, while in the 

 female the clyj^eus is somewhat broader at base, being less crowded 

 between the swollen eyes. 



Clypeus. — The clypeus is usually more or less emarginate or sub- 

 bilobed (fig. 1), although there are many species with entire clypeus 

 (figs. 2 and 3). At base the clypeus is expanded, forming a portion 

 of the canthus which invades the eye, but in the species of the tristis 

 group (fig. 2) the clypeus is coarctate at base, not extending over the 

 eye, and consequently not wider than the front. The margin of the 

 clypeus is always reflexed, in some very widely, in others scarcely 

 at all with all manner of intergrades. It has been observed that 

 those species with the narrowly reflexed border have the punctures 

 denser than those with the widely reflexed border in which the })unc- 

 tures are very often sparse. The extent of emargination sometimes 

 varies sexually, being deeper in the female (lanceolata). The punc- 

 tuation of both clyj^eus and front often varies between the sexes. 



Antenna. — It may be said, as a general rule, that the antennae 

 are longer in the male than in the female. In the vast majority of 

 species the club is much longer in the male, although in some mem- 

 bers of the creimlata group the difference is hardly perceptible. 



