RELATION OF THE TONGUE TO FOOD. 39 



teristic of the tongues of insectivorous birds, sucli as the swifts and 

 swallows. The spines of the upper surface of the tongue also reach 

 their greatest size in the Sapsucker (Sphyrapiciis), and spine-clad 

 tongues are another characteristic of insect-eating birds. The insec- 

 tivorous diet of the Sapsucker is further indicated by the fineness of 

 the backwardly directed spin 5^ processes at the base of the tongue and 

 about the opening of the trachea, their use being apparently to facili- 

 tate the passage of food past the larynx. 



The direct relation of the modifications of the tongue to the char- 

 acter of the food can perhaps be best appreciated by comparing the 

 figures of the tongue, and particularly the enlarged figures of the 

 tongue tips, with the table giving the summary of the food. It will 

 be seen, too, by further comparison that there is a direct relation 

 between the form of the bill, the tongue, and the number of larvae 

 eaten. Those species which have bills best adapted for cutting into 

 trees containing larvae, and tongues most capable of extracting them 

 from their hiding places, eat the most. Thus the Three- toed and Pile- 

 ated Woodpeckers {Picoides and Geophloeus) stand at the head of the 

 list, closely followed by the members of the genus Bryobates. At the 

 other extreme is the Sapsucker {Sphyrapicus varius), for this species 

 was only once found to have eaten larvae, and in this instance they 

 were probably not obtained by cutting into wood. It should be noted, 

 as showing the imiDortance of the modifications of the tongue, that 

 the Flicker [Colaptes), which has a curved bill, not well adapted to cut 

 into trees after grubs, has, next to the Eedhead {Melanerpes) and Sap- 

 sucker {Sphyrcqncus), eaten the smallest percentage of larvae of any 

 species examined. 



Altogether the evidence favors the view that modifications of the 

 tongue are directly related to the character of the food and are not of 

 value for classification. 



