150 PHYSIOLOGY OF INSECTS. 



unfrequently happens that these parts, namely the pro- 

 meso- and metasternum, are again intersected by lines 

 dividing them into two or four plates : if two only, the 

 plate nearest the head is termed the sternum, the other 

 the sternellum ; if four, they have been named the prcc- 

 sternum, sternum, sternellum, and poststernellum : the 

 prefixes pro, meso, and meta, signifying anterior, middle, 

 and posterior, may be united to the terms indicating the 

 sections of the segments, as well as to the segments them- 

 selves, thus we may write " the metasternellum of Hydro- 

 philus piceus terminates in an acute elongate spine," in- 

 stead of saying " the posterior portion of the sternum of 

 the metathorax of Hydrophilus &c.," the construction of 

 the word will at once carry the eye of the entomologist to 

 the part intended. 



Straus-Durckheim, in his laborious work on the anatomy 

 of the common cockchafer, has assigned names to every 

 plate into which their segments are divided ; his descrip- 

 tions are excellent, but the names, like those employed by 

 Kirby, are too fanciful for adoption, and thus his magnifi- 

 cent work, however entertaining in the abstract, is una- 

 vailable for purposes of definition. He calls the prothorax 

 the corselet, the mesothorax the prothorax, and the meta- 

 thorax he allows to retain its proper name. " The meso- 

 thorax" according to Straus, "is composed of fourteen 

 parts, besides several smaller ones connected with the 

 elytra ; the lower surface of the mesothorax is occupied 

 by the mesosternum, [F F], which, in many beetles, is so 

 closely united to the metasternum, as not to leave the least 

 trace of a suture : its form is similar to that of the pro- 

 sternum, offering a central part and two alee, with an 

 internal apophysis. On each side of the mesothorax is a 

 tetragonal plate composed of two parts, the first of which, 

 the first ilium, is united below to the alee of the mesoster- 



