ENTOMOLOGICAL NEWS. 



PHILADELPHIA, PA., JULY, 1914. 



What is a Species? 



Linnaeus wrote, in section 157 of his Philosophia Botanica 



(1750): 



There are as many species as the Infinite Being produced diverse 

 forms from the beginning; which forms, according to the fixed laws 

 of generation, produced more, but always like themselves. There- 

 fore, there are as many species as diverse forms or structures occur 

 to-day. 



Many species, as established by Linnaeus himself, were 

 divided into several species, some of which were referred to 

 one genus, some to another, by his successors, even in the first 

 half of the nineteenth century. Prof. Poulton, in his presi- 

 dential address to the Entomological Society of London in 

 ic)O4, gave many illustrations of the divergences of opinion in 

 the separation of species by the structural or form criterion. 



In the latest number of the American Naturalist (Tune, 

 1914), Prof. J. H. Gerould treats of Species-building, largely 

 with reference to his own breeding experiments with the Sul- 

 phur Butterflies. He calls the breeding-true criterion, the 

 "always like themselves" of the Linnean dictum, "an unveri- 

 fied dogma." He thinks 



The erroneous idea that Linnean species are homogeneous, well- 

 defined groups of equal importance has done much to retard progress 

 in the experimental study of evolution. The limits of a species are 

 often arbitrary, depending ultimately upon the temperament of the 

 describer, and frequently based upon ignorance of the nearest allies 

 of the individuals described, living in other parts of the world. 



The most definite criteria of species, viz. : that specific characters 

 are constant and that hybrids of Linnean species are infertile inter sc, 

 are only approximately correct .... 



Like all things else, our ideas of what constitutes a species 

 change and will continue to change. As a consequence, the 

 work of the taxonomist, the systematist, will never end as 

 long as animals and plants exist. The time never will come 

 when the status of every living thing will be definitively estab- 



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