476 M. straus-durckheim's 



What is commonly called the eciisson, {scutellum), is merely 

 a portion of this part, which is elevated, and visible between 

 the elytra. The external margin of the " limbe,'' and the 

 base of the lateral apophysis of this part, are united by a small 

 horizontal and triangular plate, to which is attached the long 

 extensor muscle of the coxa of the second pair of legs. A 

 small thread-like part, arising from the anterior angle of the 

 ecusson, and united to the first ''piece iliaque" is the anterior 

 clavicle. 



The lower part of the mesothorax is occupied by the meso- 

 sternuin, {sternum moyen), which in many Coleojjtera is so 

 closely united to the metosternum as not to leave the least 

 trace of a suture. Its form is similar to that of the prosternum, 

 offering a central part and two ake, with an internal apophysis 

 {episternale moyenne), corresponding in its situation to the 

 anterior episternal. On each side of the mesothorax is a 

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

 first ilium,^) (premiere piece iliaque), is united below to the 

 al(^ of the mesostermitn, and above to a membranous space in 

 which the elytra are fixed. The second ilium is united to the 

 first by its anterior margin ; its inferior margin closes laterally 

 the opening of the mesosternum, which receives the coxa of 

 the second pair of legs ; behind it is united by a membrane 

 to the metathorax^ and above, to the same membranous space 

 as the first ilium. At the point of union between the first and 

 second ilium, is a short apophysis, formed by a fold of their 

 margins, to which is articulated the coxa. Superiorly, this 

 fold is prolonged, and continued with the anterior margin of 

 the first ilium, sending forth two apophyses ; one {apophyse 

 transverse des iliaques) directed inward, forward and down- 

 ward, serving for an attachment to many muscles ; the other 

 {apophyse alifere du prothorax), shorter, horizontal, serving 

 as the point of articulation of the elytra. The second pair of 

 stigmata are placed in the second ilium, but are not visible 

 externally. In the supra-anterior part of the cavity, which 

 receives the coxa, is a moveable piece, analogous to the rotida 

 of the protliorax. The elytra present, near the middle of 

 their anterior margin, a strong bifurcate apophysis, receiving 



^ Not an appropriate name; for can we fancy any analogy between parts of 

 the mesothorax and metathorax of insects and the ossa iunominala of the higher 

 animals ? — D. 



