171 



account of the injuries they commit (except the Cassidians, which are 

 quite distinct from those mentioned), yet there are many others of 

 the group which feed on other native plants. Of these, I mention 

 the following species, which often attract attention by its numbers. 



Gastrophysa polygoni — Linn. 



This beautiful little species is about three-twentieths of an inch 

 long, rather more than half as wide ; the thorax nearly as wide as the 

 wing-covers. Its head, wing-covers and underside of the body, a bright, 

 polished greenish-blue color; thorax and legs an orange-red ; the first 

 joint of the antenna? brownish, the rest dull black ; feet black. 



It feeds both in the beetle and larva state on the common knot- 

 weed, and although sometimes appearing in large numbers, does not, 

 so far as known, injure any useful plant; yet it is possible it may at- 

 tack buckwheat. 



Cassedinje. (Tortoise-beetle.) 



The various species of the sub-family Cassidinx are leadily distin 

 guished by the circular form of the body, which is somewhat depressed, 

 having the margin of the thorax thinned and expanded so as to extend 

 over the head and anterior legs in a thin plate-like form, and the 

 wing-cases also expanded in a similar manner, presenting very much 

 the appearance of a common soft-shelled turtle, on which account 

 thev are often very aptly described as " turtle-shaped beetles. As all 

 these species feed upon sweet-potato vines, confining their attacks 

 almost exclusively to Corvolvulaceous plants, and so far as useful and 

 ornamental plants are concerned, to the sweet-potato and morning- 

 glory, we may give a general account of their transformations and 

 habits, and very brief descriptions of the beetles. 



The larva which feed upon the sweet-potato are broad, oval in 

 shape, and flattened, thinned toward the lateral margins which are 

 furnished with a single row of prominent spines, which are often 

 numerously barbed. According to Riley there are always (m the 

 genera cassida and Coptccycla, which include these species) thirty-two 

 of these spines, sixteen on each side. 



The fore part of the body is projected over the head which is small 

 and retractile. Thev have the usual six thoracic legs on the first 

 three segments; the last segment has projecting from its tip a •forked 

 prolongation which it has the power of turning over the back; this 

 it loads with its own excrement and then holds over the back, as sup- 

 posed by many, as a kind of sun shade, but more likely as a protec- 

 tion, from insect-eating birds. 



They continue in the larval state for about three weeks, and when 

 fullv grown attach themselves by the posterior end of the body to the 

 underside of a leaf, change to the pupa state, and in about a week 

 come forth in the beetle state. 



