NORTH AMERICAN COLEOPTERA. 
281 
Abdomen. — The principal modifications of the abdomen are due 
to sexual pecnliarities of the male, which are sufficiently described 
under the species in which they occur. Several pecnliarities have 
been observed which are not sexual. In ventralis the middle of the 
posterior edge of the second segment is free and prolonged slightly 
over the next segment ; the same is observed in the third segment, 
but in a less degree. The sides of the last ventral segment are nsnally 
simple, but in a few species (obolinm, Wahinc/liami) the edge is dis- 
tinctly serrulate. The apex of the segment is rounded or oval, ex- 
cept in a few species (conciniins, acutipennis), in which it is truncate. 
In iiiine of our species is the last ventral emarginate, as in many 
European species. 
Along the side of the abdomen there will be observed a well ele- 
vated ridge, which is sometimes interrupted on the first or second 
segments, usually more or less sinuous in front. Although variable 
within certain limits it is not sufficiently so to warrant any use of it 
in the grouping of species. This line divides the ventral segments, 
so that the upper jiortion, usually sub-elytral, has been called, for 
conveidence, the “vertical ])ortion of the segments;” it is often dif- 
ferently clothed from the inferior part of the segment. 
The suture between the first two segments is usually entirely ob- 
literated, but in Walsinghami \s visilile at the sides; in some speci- 
mens of acutipennis, and more rarely bilineatus, the suture is faintly 
indicated. The pre.sence of this suture has affi)rded Mr. Waterhouse 
the means of separating a small number from the mass of species in 
Mexico. 
Legs. — The legs in all the species are slender, and afford very few 
characters useful in separation. In a good number sexual differences 
have been observed in the tibiae, consisting of a short spine or mncro 
at the inner apical angle of the anterior tibia and sometimes {otiosus, 
etc., FI. viii, fig. 18) on all the tibiae of the male; the female tibiae 
are simple in all the species. The tarsi vary, apparently, in length. 
Apparently, because in estimating their length some comparison 
must be made with adjacent parts, and it will be found in nearly 
every case the tarsi bear the same relation in length to the tibia. 
The claws vary greatly in form, affording nsefnl characters in 
grouping the species, although the demarcation is not so sharply 
defined as to render differences primarily useful. 
In no case are the claws simple, or even approaching that condition. 
Mr. Crotch remarked that while the claws of many European species 
TR.VN.S. AM. ENT. SOC. XVIII. 
( 3 ( 3 ) 
SEPTEMBER, 1891 . 
