44 



Art. V. — Thoughts on the Geographical Distribution of 

 Insects. By Delta. 



Tramite quo tendis, majoraque viribus audes ? 



Sir, — Perhaps there is no branch of Entomology more 

 worthy of attention than the geographical distribution of in- 

 sects ; yet this is totally diregarded by almost every entomo- 

 logist. He who carefully excludes from his collection of 

 British Insects every doubtful species, arranges in his exotic 

 cabinet species after species, genus after genus, without once 

 thinking of indicating the part of the world whence they may 

 have been obtained ; or, if he does note this, it is in so general 

 a manner, that little is to be learnt from it, — a line of one of 

 six different colours, which serve to indicate Europe, Asia, 

 New Holland, Africa, and North and South America, being 

 thought abundantly sufficient. 



In Dejean's Cat. cles Coleopteres we certainly find the 

 native country of each species pointed out rather more clearly ; 

 but sometimes, even there, we are left to guess as to what part 

 of a region, extending over 50" of latitude, and as many of 

 longitude, and offering, at its two extremities, a difference of 

 30" Fah. of temperature, is the principal station of an insect. 

 Besides this deficiency in exactness, there is an omission of 

 still more consequence : — no notice is taken of the range over 

 which a species extends. 



From this want of care and accuracy in pointing out that 

 country which is the principal station of a species, and the 

 extent of its range over other countries, arise difficulties, which 

 overwhelm us in our attempts to arrive at any thing like a 

 correct view of the geography of insects ; and which, joined 

 to our limited knowledge of extra-European species, forbid 

 our speaking with confidence on any part of this subject. It 

 has been well and truly observed with regard to plants, by an 

 illustrious traveller, that it is impossible to enter fully into 

 their geography unless we are thoroughly acquainted with the 

 distinctions, the characters, and the names of each species : — 

 " Ne tamen obliviscare, quemadmodum Physiologia anima- 

 lium sine Anatome esse non potest, neque Geologia sine 

 Oryctognosia, eodem modo te Geographiam Plantarum peni- 

 tus inspicere non posse, nisi Botanicae innitens, singularum 



