THE ABDOMEN. 109 



additional and proportional consistency and firmness. This part is 

 called the BELLY (renter) in contradistinction to the upper superficies 

 corresponding with the breast, which is named the BACK (dorsuni). 



The union between the several superior and inferior segments is 

 effected in precisely the same way as between the upper and under 

 half segments, by means of a soft membrane. This connecting 

 membrane is perceptible only upon the back, and only in those 

 instances where the back is protected by hard superior wings or wing- 

 cases ; in all the rest, the posterior margin of each segment laps 

 over the commencement of the succeeding one, thus covering and 

 protecting the soft uniting membrane. If we observe the abdomen in 

 its most distended state, for example, in a gravid female, it appears as 

 a large membranous bag, covered above and beneath with equally broad 

 parallel, transversely round and convex horny plates ; or, if the horny 

 substance be considered as its fundamental material, it may be 

 compared to a horny bladder divided by parallel membranous girdles, 

 and which are also separated laterally by similar membranous stripes 

 running at right angles with the transverse parallels. 



Precisely at the points of intersection of the membranous longitudinal 

 and transverse stripes, there is placed on each side a small opening 

 surrounded by a callous margin, and which is called the air-hole, 

 STIGMA, or SPIRACLE (stigma, spiracula), which is the opening to 

 the respiratory organs ramifying throughout the body. In the usually 

 contracted state of the abdomen, the natural situation of these 

 spiracles is beneath the horny processes of the superior half segment ; 

 but in the Coleoptera with corneous elytra, they lie upon the upper 

 surface of the abdomen close to the sides, and are equally protected 

 by those organs. These spiracles, consequently, are in every instance 

 most carefully protected from external injuries. 



Other openings which lead to the intestines and the organs of 

 generation we shall notice lower down. 



The uniting membrane of the horny plates Kirby and Spence 

 call pulmonarium, from the circumstance of its containing the com- 

 mencement of the respiratory organs ; but its chief purpose being 

 evidently the union of the several horny rings, it must also justly 

 thence be called UNITING skin (conjunctiva}. In descriptive entomo- 

 logy, however, it is of but little importance, as it is never visible, being 

 always covered either by the processes of the horny segments or by the 

 wing-cases. 



