83 



SOME THOUGHTS ON THE DETERMINATION OF SPECIES. 



BY J. ALSTON MOFFAT. 



Much dissatisfaction is expressed with the determining of species in entomology on 

 the structure of the imago alone, and great advantages are anticipated when the earlier 

 stages of insects are all worked out. A laudable desire is expressed in the writings of 

 the various workers in systematic entomology to bring their methods as much into harmonv 

 with Nature as possible ; this is hopeful. A naturalist should allow no personal preference 

 for one system over another to influence him in his work ; his attitude should be to discover 

 as much as possible of Nature's mode of operation, work on parallel lines, and construct 

 his system accordingly. 



Now, as there is considerable divergence in the direction to which these labours are 

 tending, it seems to indicate that there is a decided difference of opinion about what 

 Nature's method is, or a misunderstanding of its interpretation. No one can have been 

 engaged in the investigation of any department of biology without being impressed with 

 the fact that Nature is not constructed on any principles of mathematical exactness ; 

 therefore, any system aiming at that must be, just in proportion as that is attained, arti- 

 ficial. 



Now, a form is often met with in life that seems to fit in nowhere comfortably, whilst 

 another has so many points in common with widely separated forms that it is difficult to 

 decide just where to place it ; hence, I suppose, the temptation to multiply divisions, and 

 give them places to themselves. One great objection to our present method of dividing 

 into genus and species is, that it often has the effect of separating forms in a way that 

 Nature has not. When a form is termed a " species " it stands apart from its fellows to 

 some extent ; if it is placed in a different genus it stands yet further apart. When we 

 look at a check list, with its divisions and subdivisions made with exactness, and names 

 with apparently no natural affinity, one would expect to be able to separate the various 

 parts with ease ; then look at a representative collection ; what a contrast ! To the 

 uninitiated the surprise is, where the necessity was for separating the great bulk of 

 them at all. We may in a joke tell him that in the name is easily seen the difference, 

 but we have to acknowledge that in the insect it is microscopic. But divisions have 

 to be made, and that they may be made just where Nature indicates, it is desirable that 

 those engaged in the work should know the life history of the insect, its habits and mode 

 of life, as well as its appearance in its various stages. 



A knowledge of structure only — size, form and color — is sufficient for the purpose of 

 describing and naming an insect, the object of which is future identification. If that 

 knowledge includes the earlier stages, so much the better for the purpose, but a good deal 

 more is required of him who would endeavour to give it its natural position in a system, 

 and it is unfortunate that much of this latter work has been done by those only partially 

 qualified for it ; the " mere collector " often having more knowledge of Nature than the 

 accomplished scientist. 



Do the divisions of genera and species meet the requirements of nature 1 Dividing 

 lines, to be of value, should be stable ; they look rigid ; life in Nature is never rigid, and 

 its dividing lines are of the most undulating and irregular character. Scientific terms are 

 exact, and it was found that genera and species did not meet the requirements of science, 

 so varieties were added to supplement them, and now the principal trouble centres around 

 species and varieties, no definition of the term " species " being satisfactory to all, and 

 the kinds of varieties being many, and the origin of some of them unknown. 



Our knowledge of the laws of propagation in the animal economy is principally 

 derived from the experiments with' animals in domestication, and the results attained show 

 the marvellous extent to which variation can be carried when continued for a length of 

 time, and we may safely conclude that what man cannot do in this direction Nature never 

 does. The terms used in this work are species for all forms that, when brought together- 



