NORTH AMERICAN COLEOPTERA. 181 



The first character of moment is in the structure of the scape of the 

 antennae to which Dr. LeConte (New Species, 1873, p. 229) has already 

 called attention, consisting of a prolongation inwards of the apex in a 

 submucronate manner. With this we find associated a greater elonga- 

 tion of the first joint of the hind tarsus, while it is at the same time 

 more slender. 



. The under side of the tarsal joints exhibits so much and such striking 

 variation that it is difficult to understand how it has escaped observation. 

 The usual vestiture of the under side of the tarsi is a yellowish spongy 

 pubescence. This is present on the first three joints of the tarsi in the 

 group of species of which variolnre is the centre. 



In the series of species as arranged below from annnhitnm to forte^ 

 the first joint of the hind tarsus is not spongy pubescent beneath, the 

 middle of the joint being almost smooth the sides with densely placed 

 short black hair. In many of these species the second joint has but a 

 small patch on each side. In suhrugoHum the tip of the first joint of 

 the hind tarsus has a very small spongy space. In obtusvm, spoliatum 

 and forte^ the spongy pubescence gradually disappears from the joints, 

 so that there is none whatever on forte. 



In variolnre and Ulkei it will be observed that the mesosternum 

 between the coxae is deeply grooved, while in the closely allied crassum 

 the mesosternum is rather flat. These three species are further remark- 

 able in having the surface clothed with an extremely fine pubescence and 

 the surface is microscopically punctulate. The same pubescence extends 

 on the legs. 



The lateral spine of the thorax, which plays an important part in the 

 separation of genera in various parts of the Oerambycidfe, here ceases to 

 have any value whatever, and even within specific limits we may have 

 quite an evident small spine or none whatever. 



The annulation of the antennae with cinereous bands cannot be de- 

 pended upon as the pubescence is fugitive, and if made use of otherwise 

 than as a purely specific character leads to confusion. The antennae do 

 not difi"er in length in the two sexes, but are slightly stouter in the males. 



The sexes are distinguished by the form of the last ventral segment — 

 broadly emarginate in the male and oval at tip in the female ; the form 

 of the legs — the femora are strongly clavate % , comparatively slender 

 9 ; the pygidium is usually concealed in the male, exposed in the female. 

 The females often have a smaller thorax than the males, this is espe- 

 cially observable in snhruffoanm and nrmntnm. 



