568 EXTERNAL ANATOMY OF INSECTS. 



the analogous genus Erotylus* it is convex anteriorly, 

 and posteriorly more or less rounded ; in Doryphora it 

 is a long, robust, subconical horn, often standing at an 

 angle of about 45°, overhanging the prostemum. 



In the genus last named, though its mesosternum in its 

 direction and appearance resembles that of many Peta- 

 locerous beetles, yet it is separated by an evident suture 

 from the mesostethium ; but in the last-mentioned tribe 

 its representative is a process of the latter part : yet as 

 the peristethium and mesostethium are separated by no 

 suture, though in some cases a transverse channel, and 

 in others merely a coloured line, marks the point where 

 they may be considered as soldered together, in these 

 cases the mesosternum may perhaps be said to be 

 common to both. In this great family, which includes 

 within its limits some of the most singular and wonder- 

 ful in their structure and armour, as well as some of the 

 most brilliant and beautiful of the beetle tribes, — the part 

 in question, in a vast number of cases, will enable the 

 Entomologist satisfactorily to trace its numerous groups, 

 not only where it rises or stretches out into a horn or 

 ridge, but even often where it is merely a flat space be- 

 tween the mid-legs. I shall notice some of its most 

 striking variations in this tribe. In Phanceus Jestivus, 

 and in Macraspis and Chasmodia MacLeay, it is elon- 

 gated horizontally, with the apex curving upwards ; in 



a A remarkable instance of analogy is afforded by this genus. In 

 Erotylus there are two groups ; one distinguished by gibbous elytra, 

 and the other by flatter ones. The same distinction is observable in 

 Spheniscus ; for to this genus belongs Helops fascial us Oliv., which re- 

 presents the flat Erotyli, and even individually Erotylus trifaxc'tahm 

 Oliv., E.fasciatus F, 



