ADAPTATIONS 409 



Here again is another instance of apparent over-elaboration 

 in Nature. We say apparent advisedly, for the fact that so many 

 widely different creatures have developed a highly complex 

 lingual mechanism for the capture of insect food shows that 

 these exceptions require further study. 



By way of contrast we may site the case of the Red -headed 

 Woodpecker {Melanerpes erythrocephald), which, like its con- 

 geners, possesses a protrusible tongue ostensibly for the capture of 

 insect prey, yet lives at any rate very largely, on eggs of other 

 birds, even entering hen-roosts in its quest for these delicacies ! 

 Furthermore, and perhaps as a natural sequence, it devours 

 young birds, which are killed by a blow on the head with the 

 dagger-like bill, and through the hole thus made the tongue is 

 thrust for the purpose of sucking out the brains ! It is recorded 

 that, in Ohio, a colony of Swallows, represented by some dozens 

 of nests, was so completely raided that not a single young one 

 was reared ! Occasionally frogs are eaten, perhaps by way of 

 varying the diet. We must assume that this strange departure 

 has been but recently made, for as yet the elaborate mechan- 

 ism characteristic of the Woodpecker shows no signs of de- 

 generation. 



Finally, mention must be made of that most puzzling and 

 elusive phenomenon known as Diastataxy, a name coined by 

 Dr. Chalmers Mitchell to designate the apparent absence of 

 the fifth secondary remex which is met with in nearly all 

 Neognathine birds save the Passeres, which have, in consequence, 

 what Dr. Mitchell calls a eutaxic wing. Some Families of 

 birds, as among Pigeons and Kingfishers, present both forms : 

 the Galli are all eutaxic, the nearly related Megapodes diasta- 

 taxic ; the Cranes are diastataxic, but some of the aberrant 

 types are eutaxic, and so on. In diastataxic wings, as shown 

 in the accompanying illustration, all the major coverts of the 

 forearm, save the fifth pair, embrace a quill, the fifth pair do 

 not. 



Embryology, however, seems to prove that this absence of 

 a quill, or aquintocubitalism, as it was called by earlier writers, 

 is due to the torsion and shifting of the feather papillae, and 

 hence the curious " intercalary row " of wing coverts shown in 

 our illustration. 



A considerable body of facts have been collected with regard 



