Xll INTRODUCTORY REMARKS. 



that thus compose it, and seek to discover among them natural affi- 

 nities and a natural sequence of arrangement, we find ourselves 

 involved in some difficulty. A little examination, however, teaches 

 us (as we should expect would be the case) that we can find import- 

 ant distinguishing characters in the length and dilatation of the 

 antennae, in the facies of the thorax, and especially in the form of 

 the joints of the anterior tarsi and the form of the posterior tibia ; 

 these, when based upon, and considered in conjunction with another 

 character (which is of more value even than they are), the form of the 

 palpi {especially the maxillary), afford, we believe, characters amply 

 sufficient for the establishment of well-defined genera. In the con- 

 sideration of the different forms included in this Catalogue, the 

 only genus that has in its definition presented serious difficulties is 

 the genus Hypolampsis ; it contains within it at least three slightly 

 but distinctly different forms— that of the first species (H. melanotics), 

 from Chili, that of the first section of the genus, and that of the 

 second section. Inasmuch, however, as the species of these latter 

 groups* are not, in general form, absolutely constant inter se, I have, 

 after much careful study and microscopic comparison, thought it 

 better to unite (for the present at least) all together under one single 

 genus, leaving the task of suggesting .subdivisions to future students 

 who shall have the advantage of a larger amount of materials. It is 

 probable that other genera, as Eupeges and Homammatus, will (when 

 we know more of the insect life of the New World) also require 

 subdi vision. 



* Hypolampsis pilosa, 111., also represents another (North American) modifi- 

 cation of form. 



