1912.] NATURAL SCIENCES OF PHILADELPHIA. 311 



other than Lepidoptera; but unless the birds recognized butterflies 

 in general — a group which cannot be mistaken for other insects — 

 as part of their natural prey, it is difficult to understand their eager 

 excitement at the sight of those I offered them" (p. 81 1). 57 



Before quoting further, let us look into this argument a little: 

 it is characteristic of the selectionist style. He is very charitable 

 in admitting that predatory deftness may have been acquired in 

 chasing other insects than butterflies. A little reflection will con- 

 vince anyone, be he ignorant or not concerning the important con- 

 stitutents of bird food, that butterflies even if eaten, can furnish 

 but a small percentage of bird food, namely, an amount proportional 

 to their numbers among diurnal insects as a whole. Hence a 

 correspondingly small amount of training in predatory deftness can 

 possibly have been acquired from capturing them. Pocock finds 

 it difficult to understand the eager excitement of the birds at the sight 

 of Lepidoptera, unless they recognized them as such; this after 

 telling us on the preceding page of "the exceeding keenness of the 

 birds for the insects brought to them. This was no doubt due in a 

 measure to our inability in the Gardens to feed the birds on living 

 insects other than mealworms." 



Caged canaries, sometimes become frantically excited when a 

 grasshopper or other insect is held up to the bars of their cage— 

 they may never have seen an insect in their life before, they only 

 know there is something they want. Pocock's parenthetical expres- 

 sion concerning Lepidoptera — "a group which cannot be mistaken 

 for other insects" — directly opposes many arguments by selec- 

 tionists relative to the resemblances of Sesiidse to Hymenoptera; 

 but any argument to establish the present point without reference 

 to its bearing on other phases of the theory is a long-standing rule 

 among selectionists. Continuing his argument, Pocock says: 

 "Again, unless the species of butterflies used for the experiments are, 

 or were in the past, habitually preyed upon by birds, 57 whence comes 

 the extraordinary skill the liberated specimens .... displayed in 

 dodging the swoop of birds in midair? Having repeatedly seen the 

 aim of the pursuing bird baffled by the evasive twist of the butterfly, 

 I cannot doubt that the insect's behavior was prompted by the 

 instinct to escape an habitual enemy of its species, of the same class, 

 and with the same predatory methods" (p. 811). 



57 It is worth pointing out that the disciple is here arguing directly against 

 one of the cardinal teachings of the master, as Poulton iterates and reiterates, 

 "acceptance is not proof of palatability" (Trans. Ent. Soc. Lond., 1902, pp. 436 

 317, 348, and 389). 



