THE STATE ENTOMOLOGIST. 61 



Bug. Moreover, as these Tortoise-beetles usually hide on the under 

 side of the leaves, and as the vines trail on the ground, it is very diffi- 

 cult to apply the powder without running some risk from its poison- 

 ous qualities. I therefore strongly recommend vigilance when the 

 plants are first planted, and by the figures and descriptions given 

 below the reader will be enabled to recognize and kill the few beetles 

 which at that time make their appearance, and thus nip the evil in 

 the bud. The Bermuda and Brazilian Sweet-Potato plants are more 

 vigorous than the Nansemond, and less liable to be attacked. 



THE TWO-STRIPED SWEET-POTATO BEETLE— Cassida bivittata,, Say. 



This is the most common species found upon the Sweet-Potato, 

 [Fig. 32.] and seems to be confined to that plant, as I have 



never found it on any other kind. Its transfor- 

 imations were first described by myself in the 

 I Prairie Farmer Annual, for 1868, (p. 53.) The 

 1 f larva (Fig, 27, 2 enlarged; Fig. 32, natural size), 

 J is dirty white or yellowish-white, with a more 

 -*-- • —*-._/ or l es g intense neutral-colored longitudinal line 



along the back, usually relieved by an extra light band each side. It 

 differs from the larvosof all other known species in not using its fork 

 for merdigerous purposes. Indeed, this fork is rendered useless as a 

 shield to the body, by being ever enveloped, after the first moult, in 

 the cast-off prickly skins, which are kept free from excrement. 

 Moreover, this fork is seldom held close down to the back, as in the 

 other species, but more usually at an angle of 45° over or from the 

 body, thus suggesting the idea of a handle, in Kirby & Spence's In- 

 troduction (p. 426), may be found the following passage in reference 

 to the positions in which the fork of the larvae of these Tortoise- 

 beetles is carried: "The instrument by which they effect this is an 

 anal fork, upon which they deposit their excrement, and which in 

 some is turned up and lies flat upon their backs ; and in others forms 

 different angles, from very acute to verjr obtuse, with their body ; 

 and occasionally is unbent and in the same direction with it." Reau- 

 mur is referred to as authority for these statements, and the language 

 would lead us to suppose that the forks were thus variously carried 

 by different species; but Reaumur never said anything of the sort. 

 His language has been poorly rendered, for he distinctly referred to 

 the different positions which the same insect could give to the fork, 

 and I believe that the peculiarity mentioned above has never been 

 observed in the larvae of any other species of the genus. 



When full fed, this larva attaches itself to the underside of the 

 leaf, and in two days the skin bursts open on the back, and is worked 

 down towards the tail ; when the pupa, at first pale, soon acquires a 

 dull brownish color, the narrow whitish tail, which still adheres pos- 

 teriorly, being significant of the species. See (Fig. 27, 3.) 



The beetle (Fig, 27, 4 ) is of a pale yellow, striped with black, and 

 though broader and vastly different scientifically, still bears a gen- 



