TFIE ABDOMEN OF A BKKTLK. 19 



l)aii- ])('iiiii' usnally more firmly united. On i-aisiiio- tlie elytra the 

 iiuiiiher (»r dorsal sej^iueiits visil)le is almost always greater than 

 those below, and in most cases their le.\t\ire is less dense and often 

 memhi'anous. 



The breathinti' pores or splrdclcs, opening' into the trachea' or air 

 tubes, are located in the coiu!eetin<z membrane or in the ni)])er in- 

 flexed portion of the ventral seii'ments ; an additional spiracle is 

 also usually located on the under side of the prothorax behind the 

 outer limit of the coxal cavity. 



The anal openino' is located hetween the last dorsal and the last 

 ventral aiul just below it is the o-enital openinu'. Each side of this 

 are horny valves, sometimes of very complex structure, termed the 

 genital artnatiirr. 



AVhere the dorsal seiiments are not covered by the elytra, the 

 last one is called the pi/fjidiuni and the next to last the pro'pyfjidiiini. 

 The venti'al seiiineiits may Ite either entirely free, so that the abdo- 

 men is flexihle, as in the Staphylinidte, or they may be more or less 

 closely united so that the last one alone is movable. The cross su- 

 tures conneetiuii' them are usually i)lainly visil)le. Roth they and 

 the dorsal seu'inents are, however, often punctured or otherwise 

 sculptured, and pubescent, as is also the under surface in fi-ont of 

 the abdomen. 



Styidulati)i(j (>rf/(nis, used for producing' scmnd or sexual calls, 

 are present in a number of species, but are much less common and 

 more simple than in the Orthoptera. They usually consist of fine 

 wrinkles or ridg-es placed side by side, and the sound is produced by 

 rubbing over these some other nearby portion of the body. For the 

 most part these ridges are located upon some one of the abdominal 

 segments and are rubbed by either the (dytra or the hiiul legs. 



The above constitute the more important external parts of a 

 beetle, the characters of which are used in determining its name and 

 position among the members of the order Coleoptera. As already 

 seen, these different parts vary much in size and form, but the 

 names above given to them apply as well to the members of one 

 family as to those of another. IMany other descriptive terms will 

 also be Found in the pages which follow, but they, for the most part, 

 will be self-explanatory, or will be defined in the accompanying 

 glossary. By referring to such figures as are given and by observ- 

 ing very carefully the parts of the specimen in hand, the beginner 

 need have but little hesitation in deciding as to whether the descrip- 

 tion agrees with that specimen. 



