THE PHYTOPHAGA. 139 



The third and last tribe of Beetles with four- jointed 

 tarsi consists of insects which^ although strictly vege- 

 table feeders^ differ from the beetles of the preceding 

 tribe by attacking exclusively the leaves and soft 

 green parts of plants. From this circumstance they 

 are called Phytophaga^". Like the Longicorns^ their 

 heads are not produced into a rostrum^ but their 

 mandibles are of small size^ and rarely visible when the 

 mouth is closed, and the outer lobes of the maxillae 

 are often jointed and palpiform. The antemise are 

 usually short and filiform, or slightly thickened 

 towards the tips. Most of these beetles are of small 

 size, but many of them present the most brilliant 

 metallic tints, and some must be reckoned amongst 

 the most splendid of beetles. They are generally 

 pretty active, and well provided with wings, and as 

 both they and their larvae feed upon the surface of 

 the leaves of plants, the latter are also furnished with 

 legs of a far more efficient description than those of 

 the Longicornia. The majority of the beetles are of 

 an oval form, and very convex ; in some the prothorax 

 is considerably narrower than the elytra, forming, as 

 it were, a sort of neck, whilst in others the body is 

 considerably flattened, and the margins of the elytra 

 and prothorax are greatly dilated, those of the latter 

 completely concealing the head, so that the insects have 

 somewhat the appearance of minute tortoises, whence 

 the name of Tortoise Beetles has been given to them. 

 These beetles are also called Helmet Beetles, and 

 their scientific name, Cassida, also refers to the pro- 

 tected condition of their heads. One example of this 

 curious form may be met with abundantly in the 

 early summer months upon thistles, and some other 

 * Gr. phuton, a plant, phago, to eat. 



