PREFACE. V 



that the characters used for the construction of the table are at the 

 same time the most important generic characters ; far from such 

 being the case, I have, but only in a few rare instances, tried to 

 facilitate the discrimination of genera by preferring to use charac- 

 ters applicable only to North American species (for instance 

 in the separation of Gymnoplernus from the genera immediately 

 following it). 



The merit of the adopted distribution in genera has been tested 

 and proved by the circumstance, that all the newly discovered 

 species very easily found their proper place in it. Of course, all 

 the genera cannot be considered as equally well established. 

 Above all others, the distribution of the smaller species, for the 

 most part neglected by collectors, as well as difficult to examine, 

 still offers many obscure points. This is especially meant for the 

 proper separation of the genera Chrysotus and Diaphorus. To 

 escape the difficulty of defining the proper position of some North 

 American species, showing the characters of both genera, I have 

 been obliged to draw the line between the two in a somewhat 

 different manner. The relation of the genus Hercostomus to 

 Gymnopternus is likewise not very clear. A continued study ol 

 the structure of the known species and the discovery of new ones, 

 will gradually remove this uncertainty and develop the systematic 

 arrangement, so as to keep pace with such an increase of know- 

 ledge. I think, however, that I can give in general the positive 

 assurance, that the location of the species described by me is a 

 natural and not a forced one ; the only exception is Synarthrus 

 barbatus, in which the thumb-like projection of the second anten- 

 nal joint upon the inside of the third is much smaller than in the 

 other species of this genus. I possess this species only in a single, 

 not well preserved specimen. As it can hardly be looked for in 

 any other genus but this, I have deemed it more expedient to 

 locate it provisionally here, than to found upon it a new, perhaps 

 not justifiable genus. 



I have taken pains to elucidate conscientiously the rather con- 

 siderable number of species published by former authors. Un- 

 fortunately, most of these species were described without any 

 regard to the most essential generic and specific characters, so 

 that only in a very few cases have I been able to identify them. I 

 have preferred not 10 use specific names the identification of which 



