XXVIU INTRODUCTION. 



Stridulatinrj organs, or organs for producing sound, exist in 

 various families, and consist of finely wrinkled surfaces, frequently 

 with a pearly lustre; the sound is produced by friction with some 

 other part in the vicinity of these stridulating surfaces. The 

 situation of these organs is inconstant; thus among the Scara- 

 baeidaB they are found in Trox, on the ascending portion of the 

 first ventral segment; in Strategus, on the propygidium, and in 

 Ligyrus on the inner surface of the elytra, which in many Ceram- 

 bycidiB the mesonotura in front of the scutellum is wholly or in 

 part covered vvitli a stridulating surface, the sound being pro- 

 duced by the movement of the prothorax upon it. 



Extensible vesicles are observed in one tribe of the family 

 Malachiida) ; there are two pairs, one proceeding from a fissure 

 beneath the anterior angles of the prothorax ; the other pair 

 emerging outside of and anterior to the hind coxoe. 



The above sketch of the external anatomy of Coleopterous 

 insects contains all that is necessary to enable the student to 

 comprehend the following pages. Numerous other modifications 

 of structure exist, but these are often of merely specific or sexual 

 value, and are dealt with in essays of a monographic nature. 



THE CLASSIFICATION OF COLEOPTERA. 



Few persons, except those who have been trained in the labori- 

 ous work of the laboratory and library, are aware of the immense 

 difficulty of dealing with complexes containing such vast numbers 

 of species as those which constitute the principal insect types. 

 The species represented in the collections of the authors of this 

 treatise are from our restricted fauna more than 1 1,000 in number. 



The collection and the observation in the field of these small, 

 but beautiful objects furnish a most agreeable and useful prelimi- 

 nary training to their investigation, but are in themselves, until 

 subjected to the critical revision of the student, of small value 

 for systematic or economic science, in so far as that they aid but 

 little in forming the classification and stable nomenclature, upon 

 which the knowledge of the objects treated of must rest, in order 

 to permit them to be intelligently spoken of 



This much having been premised, as showing the necessity for 

 a methodical system of arrangement, we may proceed to say that 

 all Coleoptera fall into two primary divisions : — 



