TNTRODFOTTON. IX 



not agree with the type into " aberrations " and " varieties " is to a 

 great extent artificial and arbitrary, and frequently incapable of 

 application. At the same time, I do not wish to deny the comparative 

 value of these terms when applied in a general way to local races or 

 isolated accidental forms, as the case may be. But for the purpose of 

 exact sub-division the terms are useless and cannot be scientifically 

 applied. 



USE OF THE TERM TYPE. In the preceding paragraphs concerning 

 "varieties" and "aberrations" I have frequently used the term "type." 

 In entomology this has two very distinct meanings and its application 

 in each instance from a scientific point of view can be readily justified 

 and proved to be correct. 



In the first place, the term " type " is used to designate the 

 prevalent form of any species occurring in a given district or area. 

 Thus var. suffusa is often referred to as the London type of Cuspidia 

 psi ; var. myricce is referred to as the Scotch type of Viminia euphorbia? ; 

 var. meridionalis as the Huddersfield type of Polio, flavicincta ; var. 

 mridicincta as the Portland type of Epunda Uchenea and so on. Every 

 locality, with anything specially peculiar in its environment, will 

 produce its own particular type, and hence, in this way, there will be 

 almost as many types as localities. 



Now let us first examine the usage of the term " type " in a more 

 extended manner, and let us consider what in this sense is the true 

 type of the species. As in the above examples, we restrict the term 

 " type " to the prevalent form in a certain fixed area, generally a com- 

 paratively small one, so if we wish to obtain, in this sense, an idea of 

 the true type or prevalent form of the species, we must find out what 

 is the prevalent form throughout its whole area of distribution. But, 

 as a matter of fact, we know very little of the different phases of the 

 variation of most insects throughout their whole area of distribution, 

 and hence it is, in the present state of our knowledge, almost impossible 

 to fix on the prevalent form or type of even the best-known and 

 commonest species. We know that every special locality, with any 

 striking or marked peculiarity in its environment, will produce its 

 own special form, and it would be necessary to compare all these 

 different local types to get a general idea of the type of the species as 

 a whole as used in this paragraph. 



The use of the term " type," in this sense, can only be valuable, 

 therefore, in a general way, and it contains no actual scientific value, 

 since it does not convey a definite idea to the mind of the student. 



But there is another use of the word " type " which is most 

 valuable in scientific work. The term is applied to that particular 

 form of a species which was first figured or described by an author 

 under a particular name. For the purpose of comparison it is necessary 

 to have a fixed form with which comparisons may be made, otherwise 

 we should always be hopelessly muddled. It may be an arbitrary 

 arrangement to refer to some particular form as the type, but it is 

 certainly a most useful one. The type may, in this sense, be a very 

 rare form, a very local form, or a common and well-distributed one, 

 but for the purpose of comparison it matters little which of these it is. 

 So long as we have something exact, fixed and unalterable, comparison 

 is easy ; without such, comparison is impossible. If our knowledge 

 was sufficiently advanced to enable us to refer with ease to the most 



