4 BULLETIN 145, UNITED STATES NATIONAL MUSEUM 



ate at base, with or without longitudinal costae, and the apex vari- 

 able, sometimes expanded, broadly rounded, acute, or strongly den- 

 tate. Sternal cavity formed almost entirely by the metasternum. 

 Mesosternum divided, the lateral branches very short. Prosternum 

 broad, and more or less lobed in front. Middle coxae not more 

 widely separated than the anterior ones; posterior coxae short, 

 slightly dilated internally, narrowest at middle, and strongly dilated 

 anteriorly at the lateral margin. Legs slender ; femora fusiform, not 

 dentate on inner margin, and frequently more strongly swollen in 

 the males ; tibiae slender and subcylindrical, the anterior ones some- 

 times ciliate; tarsi long and slender, and the joints armed with dis- 

 tinct lamellae, the first joint of posterior pair as long or longer than 

 the following two joints unites; tarsal claws cleft or dentate. Body 

 elongate, feebly convex, broadly rounded in front, and attenuate 

 posteriorly. 



DISCUSSION OF PARTS 



Head. — The front may be flat, moderately convex, or very convex. 

 In the latter case the mouth seems more retracted and inferior. In 

 nearly all of the species the head has a median depressed line begin- 

 ning at the occiput, but the line varies both in length and depth, 

 forming in some species a deep frontal depression, and in other 

 species the front is broadly concave. The epistoma is variable in 

 form, sometimes being very narrow between the antennal cavities, 

 and at other times distinctly transverse. Sexually the head varies 

 in color, sculpture, and in the density of the pubescence. The form 

 of the lateral margins of the front or of the eyes is of taxonomic 

 importance; some species have the front with the sides parallel to 

 each other, whereas in other species these margins are sinuate. It 

 is, however, difficult to make use of this character in the key for 

 separating species, because the front of the head is sexually variable 

 in some of the species, the males having the front rather narrow, 

 with the sides sinuate, whereas in the females the front is distinctly 

 wider, with the sides nearly parallel to each other. 



Antennae. — In some species the antennae are long and slender, 

 with the joints longer than wide; in others they are short and com- 

 paratively stout, with the joints as wide, or even wider than long. 

 The most important character is in the form of their serration, and 

 the species can be separated into two series, one in which the serra- 

 tion begins at the fourth joint, and the other with the serration 

 beginning at the fifth joint. There may be at times individual 

 specimens which might be difficult to determine to which series it 

 should be referred, but when the fourth joint resembles the fifth 

 joint more nearly than it does the third, the specimen should be 



