I have stated in the last section of the preceding chapter that insect stature is eminently beneath the control of contingences from without; adducing, amongst other examples, in support of this, the Madeiran _Ptinus albopictus_,--a species which, whilst it averages more than a line in length on the central island of the group, is reduced to _less than half_ that bulk on a small and weather-beaten rock (the Ilheo Chao) at a distance from it. Judging indeed from many hundred specimens of the _Ptini_ which I have submitted to a close comparison, "the most constant of their characters would seem to be outline and sculpture, whilst size and colour are apparently the least to be depended upon:--so that trifling differences may be of specific indication in the former case, where in the latter much larger ones are worthless[55]." I have in fact generally noticed, that size and colour are more peculiarly liable to be affected _together_. This, however, is nothing more than what we should anticipate, since the same causes which have stunted the dimensions, during a long series of ages, of any particular creature, will for the most part be found to have also impaired the brilliancy of its tints. Luxuriance of vegetation and sheltered districts are alike conducive, in the Annulosa, to the development both of the body and its adornment; or, in other words, where the vegetable creation attains its maximum (which it certainly does not do in situations which are exposed to the irritating consequences of a perpetually stormy atmosphere), there the animal world will be usually observed to thrive. There are many insects which appear to have _two distinct states_, both in magnitude and hue, which we are seldom (in some instances, I believe, never) able to unite by intermediate links, or grades; and yet which are universally admitted, although found in actually the self-same spots (a fact which prevents their being looked upon as separate, local modifications of a common type), to be mere varieties of each other. They are, however, exceptions to the general rule; and, although infringing on the strict definition of a "variety," as given at a preceding page[56], we nevertheless feel an _a priori_ conviction that they are by no means specifically dissimilar _inter se_. Such phases, as regards _stature_, are presented by the _Brachinus crepitans_ and _Lamprias chlorocephalus_ of our own country; whilst, as regards _colour_, the _Philhydrus melanocephalus_, _Aphodius plagiatus_, and the _Psylliodes erythrocephala_ (constituting in its paler garb the _P. nigricollis_, Mshm) may be quoted, as cases in point. Thus, also, in Madeira, the _Mycetoporus pronus_, Erich., has a large and small form, living in communion,--which I have never been able to connect, and yet which are unquestionably identical (differing in no respect except in size): and so have the _Stenus Heeri_, Woll., and the _Saprinus nitidulus_, Fab.[57]