8 INTRODUCTION'. 



cumstances not as reasons for rejecting the tarsi altogether 

 in arrangement, but as proving how little they are to be 

 depended on as the ground-work of primary divisions or 

 famiUes. 



In discussing the use of particular parts of an insect for 

 purposes of classification, the sternum deserves some de- 

 gree of consideration, as we find it often assuming, in the 

 Lamellicornes, Lat. a very peculiar character, which ap- 

 pears in some measure to correspond with their manner 

 of living; but the use of this part of the insect has hi- 

 therto been undiscovered. We may, however, arrive near 

 the object of our wishes on this subject, by considering 

 the construction of this organ, and the manners of the 

 various insects which possess it. On dissecting a lamel- 

 licom insect it will be found, that on the inside and from 

 the lower extremity of that ring of the abdomen which is 

 known to entomologists by the name oi pectus, there rises 

 upwards obliquely a long crustaceous triangular pyramid, 

 the apex of which is fixed to the abovementioned extremity. 

 This pyramid has the lateral angles of its base very acute, 

 and is the proper sternum of the Lamellicornes, Lat. com- 

 posing indeed the whole of it in nearly all the Scarabees de 

 terre of De Geer : but in many of the other division, com-- 

 posed of insects which feed on living plants, and which 

 I have therefore called Thaler ophaga, we find that the 

 lower acute edge of tlie pyramid is joined to the breast 

 by a thin crustaceous plate, the extremity of which ap-- 

 pears produced externally between the first pair of legs 

 into what is commonly called the sternum productum^ , 

 Jf we examine a longitudinal section of it under thia 



* Fabricius appears to have been acquainted with this external process 

 of the sternum only. " Sternum linea pectoris longitudinalis, ssepe antico 

 posticeque mucronatum, difFert quoad proportionem, apiceip," 



