12 BRITISH BEETLES. 



having numerous branched, radiating vessels, extending 

 internally. 



The attachments and development of the muscles of 

 the Cockchafer, a good type of the beetle tribe, are ad- 

 mirably' described and figured in Strauss-Diirckheim's 

 " Considerations generates sur P Anatomic comparee des 

 Animaux articules ' (Paris, 1828). 



Presuming that the student now has a general idea 

 of what is signified by the word Coleoptera, we will, 

 before entering more fully into the subdivisions of that 

 order, proceed to make some observations upon certain 

 points which it will be necessary for him to master, 

 such as the definition of a species, etc., the terms used 

 in descriptions, the names of external parts of the 

 body, the best books of reference, and the instruments 

 required, etc. 



A " species," the most simple lasting alliance of spe- 

 cimens that is usually recognized (commonly termed 

 a "sort" or "kind"), may be defined as an imaginary 

 congregation of individuals, possessed, during all the 

 stages of their existence, of an identity of habit and 

 structure, and of which the sexes confine themselves to 

 each other in breeding, These characters, nevertheless, 

 cannot always be strictly relied upon; since, under different 

 circumstances, such as the greater or less supply of their 

 natural food or necessary temperature, insects palpably 

 identical as species will often exhibit slightly unusual 

 habits, and (apart from mere sexual variation) minute 

 deviations from their normal form in size, colour, out- 

 line or sculpture. When presenting such accidental dif- 

 ferences (which, by the way, are continuous when their 

 causes remain) they are termed "races;" and a single 

 specimen is called a " variety," when it has any unusual 



