AMERICAN COLEOPTERA. 93 



If we examine that portion of the body of a Cicindelide, Carabide or 

 HaUpHde, it will be observed that the metasternum consists of two 

 distinct pieces, the anterior or that which makes up the greater part of 

 that member and .the posterior or ante-coxal piece separated from the 

 former by a well marked suture extending entirely across the body. 

 This line of separation has probably been considered merely a matter of 

 sculpture but in some Carabidae, especially the z ae n i n i, the two 

 sternal pieces may be entirely separated by a short immersion in a solu- 

 tion of caustic potassa. In fact in these last named insects I am inclined 

 to believe the suture somewhat mobile, as there is an evident laxity 

 of articulation in the side pieces of the body as well as between the 

 meso- and metasternum. The suture and piece intended will be seen 

 on PI. Ill, figs. 1—5. 



In Amphizoa and Pelobius the structure is entirely different. There 

 is but a very small ante-coxal piece with the suture in front of it very 

 indistinct and the posterior side truncate and not prolonged between 

 the coxae as will be observed in the preceding families. This gives the 

 metasternum the appearance of being truncate behind, a form of ex- 

 pression already made use of by various authors. This structure is 

 shown on PI. Ill, figs. 6 — 7. 



In the Dytiscidae and Gyrinidae with their short metasternum there 

 will be observed an entire want of any such structure. The ante-coxal 

 piece is entirely absent without trace of suture, and the metasternum is 

 pointed between the coxae. The under sides of Di/tiscus and Dineutvs 

 are represented on PI. Ill, figs. 8 — 9. 



The posterior cox?e also diifer greatly in the various families. In all 

 the coxae are contiguous except in a comparatively few Carabidac, the 

 extent of the contact varying greatly from a mere angular touching to 

 quite a long edge of contact. In the figure of Cychrus (PI. Ill, fig. 1), 

 the coxfe will be seen separated by a small triangle of the first ventral 

 segment, Pterostichus (fig. 2), and Morm.nI//ce (fig. 3), show a mere 

 point of contact, while in the other genera on the plate the extent 

 01 contiguous edge varies, being greatest in Diveutus. 



The coxae reach the side margin of the body, separating the meta- 

 sternal side pieces from the first ventral segment, in all the families 

 excepting the Carabidae and Cicindelidae. Track// park// a of the former 

 fiimily makes an exception. With this extent of the coxae externally 

 we have associated an immobility of the coxae, thus aff'ording a firm 

 point of support for the hind legs required by the mode of life of all 

 the genera possessing it. The extent of median contiguity tends to 



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