176 THE ORDER OF COLEOPTERA. 



aud 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 (Grioceris 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 1 have 

 observed the same to be true of the larvae of Blepharida rhois. 



The Cassidides jjresent four well marked genera as follows : 



A. Head prominent, Tisible ; size below medinm ; color blue Porphyeaspis. 



A A. Head partially visible ; prosternnm advanced ; size large ; red spotted witli black.. Chelymorpha. 

 AAA. Head completely concealed. 



B. Body oblong oval, convex ; size large; color dull greenish brown Phtsonota. 



B B. Body oval or orbicular, moderately convex or depressed ; size about medium ; colors 



various Cassida. 



Porphyraspis, Boheman, meaning sl purple shield, is founded upon the 

 Cassida eyanea of Say, found in the Southern States. Chelymorpha, 

 Chev., signifies literally tortoise shape. It has for its type the C. cassidea, 

 Eabr., 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, aud six on each elytron. The larva is said to feed upon the 

 milkweed. Fhysonota, Boh., meaning swollen or convex hacJc, contains 

 the P. imij)U)ictata, Say, of about the same form aud 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 black dots on the thorax. Cassida has been di- 

 vided into two sub-genera, Cassida proper having the antennjB not 

 longer than the thorax, and usually of a sub-convex, oval form ; and 

 Coptocycla, with the antennae longer than the thorax, aud usually of an 

 orbicular and depressed form. The species which occur iu this section 

 of country may be tabulated as follows : 



