INTRODUCTION. XIX 



Between the ligula and nientum are the supports of the labial 

 palpi ; these sometimes are largely developed, and in certain 

 ^carabseidiB are entirely united together, forming what appears 

 to be the ligula ; the genuine ligula in these cases is almost 

 atrophied, and is concealed behind the corneous plate formed by 

 the labial supports. In the following pages the term ligula is 

 used in both cases, and is to be understood to mean the piece in 

 front of the meiituni bearing the palpi, whether it \)o ligula [jroper 

 or some other part. 



The labial i)alpi are usually o-jointed, but occasionally 2-jointed 

 or even, in certain Staphylinidse, filamentous, and not divided 

 into joints. In the genus Aleochara they become 4-jointed, by 

 the addition of a minute terminal joint. The terminal joint is 

 usually of the same form as that of the maxillary palpi ; it, how- 

 ever, differs in many genera of Carabidae and Clerida3. Characters 

 of great value in classification have been derived from the form 

 of the labial palpi. 



THORAX. 



The second division of the body is called the thorax, and con- 

 sists of three segments, and which are variously modified as 

 regards size and union in the different orders of insects. 



In Coleoptera the first of these segments, the prothorax is 

 separate from the other two, and is usually freely movable ; it 

 consists of a dorsal surface, the pronotum, of but one piece, which 

 in other orders is sometimes divided into four parts; at the sides 

 the dorsal surface is usually inflexed, forming part of the under 

 surface of the prothorax, the acute margin, when it exists, not 

 always limiting the pronotum; this inflexed portion is often called 

 the pfothoracic epipleura. The under side of the prothorax 

 consists of a central member and a pair of pieces on each side ; 

 the first is the py-ostej'num, situated in front of the coxte and 

 usually extending between them. The lateral pairs of ])ieces are 

 best seen in the Carabidsc, the anterior is called the epixternum, 

 the posterior the e-jyimeron. Most frequently the sutures between 

 these pieces, and Ijctween them and the pronotum are entirely 

 effaced, so that the dorsal surface and the flanks form, apparently, 

 a continuous piece; the sutures separating the prosternnm and 

 side pieces are more often visible, and are called the prodernal 



