320 THE entomologist's recokd. 



the author considers that such criteria can, in the discrimination o 

 species, supply the place of those of morphology. 



This inference, and the fact the same principle has been invoked 

 in the case of other species of coleoptera, difficult otherwise to separate, 

 is the, perhaps, inadequate occasion for the following remarks. In this 

 enquiry, what exactly a species as an objective reality may be need not 

 detain us. The hypothesis is convenient, if not necessary, for any 

 systematic study of nature and its generally accepted test that of 

 fertility inter se, sterility inter alios. It is, however, evident that this 

 test cannot be applied to the great majority of the objects of the study 

 of entomologists. As a matter of fact, we rely for our specific differ- 

 entiations almost entirely on morphology and accept sterility, betAveen 

 what we call different species quite inferentially. 



In spite of this, however, there is no doubt but that the idea of 

 species is based essentially on a physiological, not a morphological, 

 difference, although at the same time we may suspect that physiology 

 itself might, in its ultimate analysis, be expressed in terms of morpho- 

 logy, coincident, if not dependent, as its conditions probably are, on 

 cell constituents or cellular arrangements. This, hoAvever, is perhaps 

 somewhat beside the present enquiry, which is to discover how far 

 justified is the appeal to physiology to supply criteria which morpho- 

 logy fails to give — the cases in point being certain forms of quasi- 

 parasitical coleoptera. Now the reasoning adopted by such apologists 

 seems to be that difference of habitat implies difference of habit, and 

 that this difference of habit involves a physiological disparity which 

 would include such a generative incompatibility as would make the 

 difference specific. 



Does then a different habitat imply a different habit ? In the cases 

 under discussion a difference of habitat means the nest of a different 

 species of ant, and by habit I understand that stereotyped direction 

 which co-ordinated cell-functions take, common to a group of in- 

 dividuals expressed and controlled by the nervous system. 



I imagine, however, that no one knows better than Mr. Donisthorpe, 

 admittedly our first authority, in this country, on the myrmecophilous 

 coleoptera, that it necessarily and invariably does nothing of the kind. 

 No sane entomologist, for instance, would assert that the form known 

 as Myrmedonia humeralis, when found associated with the ant Formica 

 rufa, is specifically distinct from the similar form found with Lasius 

 fuliginosHs. In fact, it appears to me that before any connection can 

 be asserted between habitat and habit, in these cases, we require to 

 know much more than we do at present as to the terms of associa- 

 tion, the conditions of the social contract which exists between 

 beetle and ant. That such terms are, in many cases, at most generic, 

 as regards the hosts, we have evidence, and, until we know exactly why 

 they are not so in all, it appears to me we are hardly justified in 

 assuming for a Dinarda what we cannot claim for an Atemeles or a 

 Glaviger. 



There are, however, other quasi-parasitical coleoptera than those 

 associated Avith ants. There are special and very closely related beetles 

 which haunt the nests of birds and of mammals, and here, I think, the 

 case may be different. The disparity between say the nest of a tomtit 

 and that of a mole, must be far more complete than between the nests 

 of any two species of ant — the environment must differ essentially, 



