326 On the Impediments to the Study of Natural History. 



modern and excessive refinements, little reliance can be placed 

 upon them. Superficial readers may not perhaps be aware 

 that most of the systems in Entomology, are made in great 

 measure to depend on a thorough knowledge of most elabo- 

 rate anatomical descriptions: "cujusque vel minimi discri- 

 minis diligentissima observatio*," the essential points depend- 

 ing, as in the case of Fabricius, upon such minute parts of the 

 mouths of insects as are not visible without a compound mi- 

 croscope, and even then not without the most careful dissec- 

 tion by a skilful and accustomed hand. 



But there are multitudes of cases in which all this skill and 

 care and microscopic observation must go unrewarded. Take 

 as an example the first entomological plate given in Swain- 

 son's valuable Zoological Illustrations, Colias Statira, Ex- 

 perienced naturalists need not be informed that the palpi of 

 the Papilionidae are looked upon as features of great authority 

 in the subdivisions of the tribe; and consequently on turning 

 to Godartf, who with some trifling variations adopts the sy- 

 stem of Cuvier and Latreille, we find the palpi occupying the 

 first place in ascertaining the generic character, and thus 

 mentioned "Genus Colias Palpes inferieurs tres-com- 

 primes ; leur dernier article beaucoup moins long que le pre- 

 cedent." In strict conformity with these and other equally 

 good authorities Mr. Swainson commences the generic cha- 

 racter of the Colias, with Palpi breves. But on reading his de- 

 scription of this very first illustration of the genus ; what do 

 we find what, but that the last joints of these palpi are extra- 

 ordinarily prolonged !, and that a similar prolongation is the 

 characteristic distinction of the Colias Drya of Fabricius, a to- 

 tally different insect. Well may he, in stating candidly (with- 

 out blinking the difficulty) that this prolongation of a promi- 

 nent generic feature is at variance with the generic character 

 of the Colias, add with equal candour, that this is a striking 

 proof that in a natural system, no single part can be taken as 

 an unerring criterion for generic distinction, without making 

 it eventually an artificial one. Again ; in speaking of the 

 Ismene (Edipodea he remarks, that although the perfect insect 

 possesses striking and peculiar generic characters, neither the 

 caterpillar nor chrysalis appears to differ from others of this 

 family of Papilionida ; adding, that this is one of the many 

 facts which prove the impossibility of making the larvae a 

 primary consideration in forming the genera of Lepidoptera. 

 It may be further observed, by the by, that here, as well as in 

 some other instances, the dissection of the mouth was omitted, 



* Latreille. f Tableau Methodiqiie dcs Lepidopteres. 



for 



