THE ORDER OF COLEOPTERA. 
176 
;iud other plants of the composite family, but most of the American 
species are found on different species of convolvulus, especially the 
morning-glory and the sweet-potatoe, both of which belong to this genus 
of plants. The leaves of these plants are often riddled with holes, and 
seriously injured by these insects. 
It is in this family that the habit of the larvae of covering themselves 
with their own excrement is most conspicuous and universal. Other 
larvae ( Crioceris and BlepharidaJ, which have this habit, void their ex- 
crement directly upon their backs, but the larvae of Cassida support 
their excrement on a long forked process which issues from the body 
just above the anal aperture, and is directed forwards over the body 
like a parasol. The object of this singular habit is supposed to be to 
protect the insects either from birds and other natural enemies, or from 
the direct rays of the sun. The former is probably the true explanation. 
That it can not be the latter, seems to be proved by the practice of 
most of these larvae of feeding upon the under side of the leaves where 
the direct rays of the sun cannot reach them. Mr. Riley has stated 
this to be the habit of the larvae of many of the Cassidides, and I have 
observed the same to be true of the larvae of Blepharida rhois. 
The Cassidides present four well marked genera as follows : 
A. Head prominent, visible ; size below medium ; color blue Porphyraspis. 
A A. Head partially visible ; prosternum advanced ; size large ; red spotted with black. .Chelymorpha. 
AAA. Head completely concealed. 
B. Body oblong oval, convex ; size large ; color dull greenish brown Piiysonota. 
B B. Body oval or orbicular, moderately convex or depressed ; size about medium ; colors 
various Cabsida. 
Porphyraspis , Boheman, meaning & purple shield, is founded upon the 
Cassida cyanea of Say, found in the Southern States. Chelymorpha, 
Ohev., signifies literally tortoise shape. It has for its type the C. cassidea, 
Fabr., subsequently named cribraria, by the same author. It is also the 
C. argus of Herbst. It is about four-tenths of an inch long, of an ob- 
long oval, convex form, brick-red, with four or six black dots on the 
thorax, and six on each elytron. The larva is said to feed upon the 
milkweed. Physonota, Boh., meaning sicollen or convex back, contains 
the P. nnipunctata, Say, of about the same form and size as the preced- 
ing species, but the head is completely hidden under the anterior 
margin of the thorax. It is of a dull greenish or yellowish-brown color, 
with one, three, or five blade dots on the thorax. Cassida has been di- 
vided into two sub-genera, Cassida proper having the antenna; not 
longer than the thorax, and usually of a sub-convex, oval form ; and 
Coptocycla, with the antennae longer than the thorax, and usually of an 
orbicular and depressed form. The species which occur in this section 
of country may be tabulated as follows : 
