in subtlety and power."[1] This argument, if it could be substantiated, appears to be, and has always impressed the writer, as one of the most complete answers to the whole theory of the protective meaning of these disguises. For if by the slow process of adaptation all variations tending to these disguises were increased and perpetuated by the process we express as "natural selection," thus ever helping the "survival of the fittest," and at the same time these changes or developments were equally studied and more keenly detected by the attentive and hungry host of insect enemies, the relations between the attackers and the attacked, the eaters and the eaten, would remain much the same at the commencement and end of the process. And therefore what becomes of Prof. Drummond's conception of mimicry, with its "practical gain," if the enemies sought, or supposed to be deceived thereby have their penetrating faculties continually increasing in subtlety and power? A moth, Agrotis cursoria, not uncommon to the sand-hills on the coast of our own country, "hides in the daytime in dense tufts of Ammophila arundinacea (Marram grass) close to the surface of the sand, and among other plants on the sea sand-hills." But "its partiality for this shelter is apparently well known to the birds, as is testified by the numbers of detached wings to be seen lying about."[2] Mr. Rodway gives a similar experience in the Guiana Forest:—"Invisibility is a striking characteristic of every living thing in the forest. At first a stranger observes nothing but a scene of desolate confusion. Later, however, he begins to distinguish one tree from another, and learns where to look for a particular animal. Then he wonders how he could have missed the signs which now impress themselves upon his eyes."[3] It is similar to the extra thickness in the armour of the ironclad, which is always influencing the construction of guns possessing greater penetrating power. It is like the acquired aptitude of the village
- ↑ 'Tropical Africa,' 4th edit. p. 180. A similar opinion was expressed by the late Fras. Pascoe: "It is not likely that animals whose lives depend on their sight should be easily deceived; though with our mostly unobservant eyes a green caterpillar on a green leaf may easily escape notice" ('A Summary of the Darwinian Theory of the Origin of Species,' p. 13).
- ↑ C.G. Barrett, 'The Lepidoptera of the British Islands,' vol. iii. p. 330.
- ↑ 'In the Guiana Forest,' p. 48.
