XI \ r 



INTRODUCTION. 



appreciable characteristics. They often discover themselves m 

 certain characteristics of appearance, which are at times of great 

 importance, but which are not seized at a glance, or in certain 

 relationships of form, which a long practice teaches one to dis- 

 tinguish easily, though they can scarcely be defined. 



The first basis of philosophical zoology is the profound knowl- 

 edge of the detail of fauna. To give as complete an idea as 

 "possible of the fauna of the Vespid;e of America is the purpose 

 of this volume. 



PLAN OF THE WORK. 



The plan which I have decided on, in drawing up this work, is 



the following:— .... c ^ a 



I give as much as possible, a complete description of the 

 species which belong to the fauna of North America, considering 

 as such all those which people the new continent to the north 

 of the isthmus of Panama, including likewise the Antilles. This 

 work is, therefore, more especially a monograph of the Vespid* 

 of the United States, of Mexico, and of the Antilles. Besides, I 

 have added, as a complement, a catalogue of all the species 

 known till now in the rest of America, and have found it a great 

 advantage in the classification, the method thus becoming more 

 complete. Moreover, this plan allows me to enunciate views on 

 the geography of insects, on the dispersion of the species, and on 

 the modifications which take rise under the influence of diverse 



latitudes. 



I have confined myself, among the species of South America, 

 to cataloguing them, not having sufficient materials to make a 

 monograph. However, for those of which I had the types 

 beneath my eyes I have given Latin diagnoses, in order to 

 describe them in a comparative manner with respect to the 

 surrounding species, and, also, in order to complete my anterior 

 studies on these insects, to 'review them and render the use more 



easy. • „ 



I think myself bound to add here, that, as to my method ot 

 description, I describe the species as far as possible in a relative 

 manner Descriptions made in an absolute sense have always 

 appeared to me less useful, because they insist on many useless 

 characteristics and often omit the most important. The reader 



