Mr. Westwood's Observations on the Genus Derbe. 3 



ciple relative to the selection of tiie typical species in genera, established by our 

 predecessors, which combined several distinct forms under one generic name. 

 For this purpose, I have considered that the species which could be proved to 

 have been more especially under the examination of the founder of such genera, 

 ought to retain the old generic name ; and where this could not be learned 

 from any particular expression, that we should resort to the first species in the 

 genus. In the writings of Fabricius we almost invariably find that he had par- 

 ticularly examined one species in each genus, as he adds a detailed description 

 of the various organs of its mouth to the description of the species, instead of 

 giving it amongst the generic characters. In such case, it appears to me clear 

 that we ought always to consider that insect as the type of the genus ; and it 

 further happens, (which is not always the case in other genera,) that in the 

 genus Derbe the species thus determined as the type stands at the head of the 

 genus ; so that in this and other analogous cases there is no ground for our 

 conferring the old generic name on any of his species, which, in our modern 

 view of such groups, does not accord with the actually determined type. 

 These observations must of course be regarded as bearing upon the subject 

 independently of the natural arrangement of objects, whereby it may happen 

 that the species thus selected as the type of a genus may not be its natural 

 type ; but still the advantages to be gained by adopting a uniform method in 

 dealing with these old generic names are so great, that naturalists will doubt- 

 less join with me in preventing, as far as possible, a still further increase of 

 the confusion in the nomenclature of generic groups. 



The type of the genus Derbe is evidently, therefore, this first Fabrician spe- 

 cies, namely, D. hcemorrhoidalis, a South American insect, to which is referred 

 by Fabricius (but with an expression of doubt) StoU's figure 160, which repre- 

 sents a species from Surinam, but which is regarded by Dr. Klug as distinct, 

 under the name of D. nervosa (Burmeister, ' Handb. d. Entomol.' ii. p. 154). 

 These two species, with the two others subsequently described, constitute a 

 distinct group, for which I consider that the typical generic name Derbe 

 ought to be retained, and the insects themselves to be regarded as the types 

 of the higher group or subfamily to which they belong. 



The insect figured by M. Perch^ron (Z). pallida, Fab.), although agreeing 

 with these typical species in the structure of the head, rostrum and antennae, 



b2 



