TETRAMEROITS PLANT-BEETLES. 175 



Wholly black: nigrita, OH v., 0.16. 

 Black varied with red : 



Thorax red and elytra black: bicolor, Oliv., 0.25: Ariadne, Newm., 0.18 : Walshii, Crotch, 0.14 : 

 Lecontei, Baly, 0.20. 



Thorax red only at the sides, elytra black : notata, Oliv., 0.24. 



Sides of thorax and shoulders of elytra red : scapularii, Oliv., 0.25: omogera, Crotch., 0.31. 

 Wholly or mostly red : 



Wholly red: rubra, Weber, 0.20. 



Ked with a black suture : Harrisii, Crotch, 0.24. 



Ked usually with obscure brown or blackish spots: quadrata, Fab., 24 : rosea, Web., 0.15. 



Microrho2Jala, Chev., (meaning a little club,) is distinguished by having 

 the antennae apparently 8-jointed, the four last joints being consolidated, 

 to which the generic name refers. The sculpture is usually either irreg- 

 ular or imperfect, as expressed in the following table of species : 



Ribs of elytra indistinct, and with fewer punctures. 



Thorax and stripe on base of elytra red: vittata, Fab., and variety Icetula, Lee, 0.23. 



Sides only of thorax and stripe on elytra red : xerene, Newm., 0.17. 

 Kibs more or less confounded with the few and large punctures: 



Punctures moderate and somewhat regular, color blue: cyanea, Say, 0.23. 



Punctures very large and confluent, color black: excavata, Oliv., 0.20. 



Surface rugulose in all directions ; black with front of thorax ; scutellum and base of antennae 

 orange: plicatula. Fab., 0.20. 

 Ribs and punctures regular and distinct : 



Color black: porcata, Melsh., 0.13. 



Color red with obscure spots : Melsheimeri, Crotch, 0. 13. 



Most of these species are widely distributed east of the Mississippi 

 river, but a few of them, f nigrita, notata, and plicatula J have as yet been 

 observed only in the Southern States. 



Sub-family CASSIDIDES. 



This sub-family is founded upon the genus Cassida of Linnaeus, a term 

 derived apparently from the Latin cassida — a helmet. They are easily 



recognized by their rounded and usually 

 more or less flattened form, the thorax and 

 elytra being dilated into a broad thin mar- 

 gin, beneath which the head and limbs are 

 retractile so as to be sometimes partially, 

 _ but usuallv wholly concealed. In this re- 

 spect some of them bear a close resemblance 



CASsmA BiviTTATA, Say:— 2, larva ; 3, , . ^, „ i ,, 



pupa; 4, beetle-after Riley. to some of the genera 01 scavcuger bcetles, 



such as Peltis, Thymalus and Nitidula, but from these they can be read- 

 ily distinguished by their strongly dilated and deeply bilobed tarsi, and 

 their antennae not abruptly enlarged at the tip. They are of medium 

 or rather large size, and are often prettily colored. A few species are 

 extremely brilliant, resembling drops of burnished gold, but this bril- 

 liancy appears to be in some way dependent upon the vital functions, 

 as it disappears immediately after death. The larvae are oval, flattened, 

 prickly grubs, feeding upon the surface of leaves, often in company 

 with the perfect insects. Many of the foreign species feed upon thistles 



