WOODPECKERS. 



425 



peckers feed. Large salivary glands (also indicated in the diagram) serve for lubri- 

 cating the sliding tongue, and it has been demonstrated that the shortening of the 

 extensor muscles simultaneously exerts the necessary pressure upon the glands. 



The woodpeckers form a very isolated group of at least three hundred and fifty 

 species, the geographical distribution of which is very interesting. They are most 

 numerous in South America and the Oriental region, less abundant in Africa, the 

 Palaearctic, and North America. It is a very significant fact that they are entirely 

 absent from Madagascar and the whole Australian region, except in Celebes and 

 Flores, both of which were, probably, never connected with the Papu-Australian main- 

 land, and which are situated so close to the Indo-Malayan islands that it is safe to 

 conclude that their woodpeckers are comparatively recent immigrations from the latter. 



We recognize three sub-families, the most generalized of which is that of the 

 Picumninae, a not numerous group of soft-tailed woodpeckers from the tropical zones 



\--em 



Ji 



tk 



FIG. 213. Diagrams showing (A) the extensile tongue of Picus from below; em, extensor muscles; f, base of 

 tongue ; sr/, salivary glands ; th, thyrohyals ; and (D) the tongue bones of Picus from the side ; chy, ceratohyal ; 

 bhy, basihyal ; br 1 and br-, thyrohyals. 



of both hemispheres. Parker regards their palate as the " most embryonic and least 

 specialized," comparing it with that of the rhynchosaurian lizards and the passerine 

 Cotingidae. The inner edges of the hind part of the palatines are greatly expanded 

 posteriorly and bent over so as to form two post-palatal flanges, as in the Cotingidae 

 and allies, as well as in the lyre-bird (Menura). Of Picnnimts, Professor Parker 

 finally says : " Altogether, this small, far-western type is extremely instructive, and 

 helps to lead the imagination down to extinct types in which the characters of the 

 hemipod, the low passerine, and the woodpecker were existent in one generalized 

 form, a form and a type only a step or two .-ibove the raft-breasted ostrich tribe/' 



The great antiquity of the piculets, as the Picumnina? are sometimes called, is also 

 indicated by their geographical distribution. South America possesses by far the 

 greater number of species, perhaps a score; four or five belong to the Oriental region, 

 and one, Verreauxia africana, hails from western Africa. 



Externally these birds differ from the other woodpeckers chiefly in their diminu- 

 tive size, and the structure of the tail, which is short and composed of normal, that is, 



