TETRAMEROUS PLANT-BEETLES. 
177 
Cassida proper. 
nigripes, Oliv.; length one-fourth inch or less ; dull red, with three obscure black dots on each ely- 
tron, in a triangle ; puncto-striate. The pallida, Herbst, is probably a pale variety of this. 
bivittata, Say ; length two-tenth inch ; thorax dull red ; elytra yellow, with a black suture and two 
black stripes on each ; puncto-striate. 
thoracica , Boh.; length three-tenth inch ; pale green, region of the scutellnm obscure brownish ; ir- 
regularly punctate. 
Coptocycla. 
aurichalcea, Fab.; length less than one-fourth inch ; golden yellow, pale yellow after death, puncto- 
striate. 
clavata , Fab.; length more than one-fourth inch ; uneven, dark brown ; margin of thorax and middle 
and tip of margin of elytra, pale transparent. 
guttata, Oliv.; length less than one-fourth inch; varying from pale brown to blackish brown, some- 
times spotted with yellow; the whole margin, except the shoulders of elytra, pale transparent. 
purpurata, Boll.; less than one-fourth inch; brownish red with a lateral triangular transparent 
patch; rare. 
Section IV. TRIMERA. 
Apparently three joints in all the tarsi, except the JErotylidce, which have four or five; the joints 
dilated and brush-like beneath, with the penultimate usually bilobed. 
This, like the other primary sections of the Coleoptera, is based upon 
the apparent number of joints in the tarsi. We have stated in the in- 
troductory part of this treatise that the highest, and what may there- 
fore be called the normal or typical number of joints in the feet of the 
Coleoptera, is five, and that whenever there appears to be a lesser num- 
ber the rudiments of the deficient joints, or a part of them, can usually 
be detected by close inspection. The present, or trimerous section, is 
less perfect or more exceptional in proportion to the number of the spe- 
cies, than any of the preceding sections, that is to say, a considerable 
number of genera and species which require to be associated with the 
trimerous beetles in consideration of their general ^structure, have four 
distinct joints in their tarsi, besides the indistinct rudiment of the miss- 
ing and penultimate joiut. 
The antennae are almost always clubbed at the eud and the tarsi are 
dilated, bilobed, and with a brush of hairs on the under side. The first 
of these characters allies them to the club-horned scavengers and dis- 
tinguishes them from the Chrysomelidae, whilst the latter character 
allies them to the last named family and at the same time distinguishes 
them from the Clavicornes proper. The great majority of them are re- 
markable for the very wide terminal joint of the maxillary palpi. They 
are almost always of small or moderate size. 
This section is much smaller than the others, and contains but two 
tribes, which bear but little resemblance to each other in form, and are 
wholly unlike in their habits. 
—23 
