260 THE BUTTERFLIES OF NEW ENGLAND. 



EXCURSUS VIII.—THE MEANS EMPLOYED BY BUTTERFLIES 

 OF THE GENUS BASILARCHIA FOR THE PER- 

 PETUATION OF THE SPECIES. 



. . , nature uever lentls 

 The smallest scruple of her excellence, 

 But, like a thrifty goddess, she determines 

 Herself the glory of a creditor, 

 Both thanks and use, 



Shakespeare. — Measm-e for Measure. 



The power of reproduction conceded, the universal instinct for self- 

 preservation is the fundamental and controlling principle by which the 

 perpetuation of any kind of animal is successfully reached. The uncon- 

 trollable maternal instinct of self-sacrifice existing in some animals alone 

 overmasters it, and this exists only in the higher animals, which, com- 

 pared with the great mass, are but few in number ; and is then in most 

 cases called into play only when the creature's life-work is nearly finished. 

 No such instinct occurs among buttei-flies, nor is in any way likely to be 

 found, so that " self-preservation" and " perpetuation of the species " are 

 here, at least through all but the closing days of life, practically equivalent 

 terms. The " struggle for existence " in the species and in the individual 

 are largely convertible terms. 



This struggle is the perpetual inheritance of the individual. The in- 

 dividual inherits alike its structure and its habits of life, which latter are 

 very largely, perhaps almost absolutely, dependent on its structure ; its 

 tastes and its propensities, its fears and its devices to circumvent its 

 enemies ; all its instincts, which are to a great extent, possibly wholly, 

 the entailment of ancestral habits ; its very attitudes, whether at rest or in 

 motion. Its advantages and its disadvantages are thus alilie its legacy; 

 so too the peculiar means it employs to disembarrass itself of these disad- 

 vantao-es. This is especially and more immediately true of the insect in 

 its earlier stages, where freedom to change the immediate surroundings is 

 exceedino-ly limited or altogether impossible, except so far as there is fore- 

 sio-ht, or an instinct marvellously akin to foresight, on the part of the 

 creature in an antecedent stage. 



It is of more than usual interest to study the means of self-preservation 

 in the o-enus Basilarchia, since there is hardly another genus of our butter- 

 flies where throughout its entire life the insect is apparently so exposed to 

 its enemies. They are all, of their kind, conspicuous objects even to our 

 dull eyes, and more than that they are, with the exception of the chrysalis, 

 always found in unusually conspicuous situations. How then do they 

 manage to escape their keen sighted foes, the birds ; or their wakeful, 

 indefiitigable, persistent enemies among the insect tribes, — ichneumons, 

 ants, wasps, flies, mites, and spiders? 



