4 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 79 



The elytra are subparallel, with a narrow margin, and are con- 

 fusedly punctate, the sculpture varying from very finely to rather 

 coarsely rugose, and, except in one or two species, they are always 

 more or less j)ubescent. In markings the species may be superficially 

 divided into three classes — the vittate; the unicolorous, except for 

 the pale margin ; and the pale-brown desert species, in which the only 

 traces of vittation are variable shoulder streaks and darkened sutural 

 margins. The most common and typical pattern, as denoted by the 

 generic name, is the trivittate form, with common sutural vitta and 

 two lateral vittae always found in canadensis and nitidicollis. When 

 the vittae begin to coalesce, there are specimens with traces of a 

 median vitta, such as occurs commonly in diducta and geminata and 

 occasionally even in lewisii and confusa. When the median pale 

 area is reduced still more, such examples occur as the vittate con- 

 vergens, neoscotiae, and many specimens of lewisii. A still further 

 development of the dark vittae results in reducing the pale median 

 area to a degree that is typical of such species as hacharidis, atten- 

 uata^ and pilosa. Then come the species with the elytra entirely 

 dark except for the margin. But in each species, with few excep- 

 tions, a varying degree of vittation is found. For instance, both 

 vittate and entirely dark specimens may be found in convergens^ 

 luteodncta^ eonfusa.^ and sericotrachyla. In the other direction, 

 there are the pale, faded-out, arid-country forms with only remnants 

 of vittae, such as nigrohimieralis and eriodictyonis. The best illus- 

 tration of variation within a species among these is geminata., which 

 ordinarily has lateral, sutural, and an abbreviated median vitta, but 

 may have only a lateral and sutural vitta (in one specimen in the 

 collection of the University of Kansas), or may lack all trace of 

 vittation except for a darkened humeral spot, or, again, the elytra 

 maj' be nearly piceous. In fact, canadensis and nitidicollis are ex- 

 ceptional in not having various degrees of coalescence in their vittate 

 markings. The elytra as a whole are pale brown or yellow, with 

 piceous, black, metallic-blue, green, violet, or deep indigo markings. 

 The species occurring east of the Mississippi River (with the excep- 

 tion of neoscotiae., in which the vittae appear almost black in some 

 lights but are really deep blue or green) all have piceous markings 

 without metallic luster. A few are very shining and brilliant, but 

 the majority, because of the pubescence and alutaceous surface, are 

 duller. The dried museum specimens, for the most part, are drab 

 and collapsed, but the fresh specimens are beautifully colored. The 

 original color as well as the shape in this genus is best j)reserved 

 by putting the fresh specimens in formalin for a few days. 



The body beneath is pale, often with darker margins and some- 

 times with entirely dark metasternum and abdomen, frequently with 

 a metallic luster. The legs are usually pale, but in some species 



