EEPOET OF THE SECRETARY. 21 



my previous studies of these insects, as well as to resume them and 

 render their use more easy. 



" I think myself bound to add here that as to my method of descrip- 

 tion, I describe as much as possible the species in a relative manner. 

 Descriptions made in an absolute sense have always appeared to me less 

 useful, because they insist on many noseless characteristics and omit 

 often the most important. The reader will not, therefore, l>e surprised 

 at my not repeating, with respect to genera, the characteristics proper 

 to every species or to the greatest number. In short, there are still 

 other characteristics which I pass over, considering them rather useless, 

 either on account of their constancy (such as the presence of silky hairs 

 on the tibiae) or on account of their variableness, such as the color of 

 the lower surface of the abdomen. 



" Descriptions are often made tedious by means of these superfluous 

 indications and thus the essential characteristics are drowned in useless 

 developments. In this way, precision is impaired instead of being 

 increased. Doubtless, here again nothing is absolute. Certain isolated 

 species may be sufficiently characterized by some salient traits, while 

 others, surrounded by very closely connected species, require minute 

 descriptions. 



"Absolute and very detailed descriptions ought, in my opinion, to be 

 employed when one describes a species isolatedly without knowing the 

 most closely connected types, (for instance in the publications of geo- 

 graphical expeditions.) It is the monographers duty to eliminate from 

 these descriptions both the common-place and the useless. But in a 

 monograph, the species are to be examined in a comparative manner 

 and relatively to the adjacent types. 



" The first condition of good comparative diagnoses resides in a wise 

 co-ordination of the species which by way of exclusion may lead to 

 choosing only between a small number of sj^ecies. Though I do not 

 like to find fault, I cannot, however, on this score, help complaining of 

 the works in which the species, though described in an absolute manner, 

 (that is by themselves and not comparatively with others,) are jumbled 

 up together, without order, without division of genera, often in defiance 

 ot the most salient characteristics. 



'^ Such works, got up in a hurry, the plans of which are laid down with 

 a view to the convenience of the authors and not for that of the readers, 

 cause the latter to lose much valuable time with no great result. They 

 do not come uj) to the precision now required by the progress of science, 

 and they are, therefore, behind their time. The reader cannot occupy 

 bis mind with incomplete works, nor can he waste his time in striving 

 to. find out species which are not to be found out 5 for there is no doing ' 

 impossibilities. - ' 



" In most of my descriptions I have been especially attentive to Wri^ 

 forms and characteristics of the form and marking, attributing to the 

 color only a secondary importance, on account of its frequent variable- 



