WOODPECKERS. 



425 



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

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

 extensor muscles sinudlaneously exerts the necessary pressure upon the glands. 



The woodi)eekers 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 

 Pala?arctic, 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 

 Floros, both of which were, ]>robal(ly, 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 

 Picumiiin£E, a not numerous group of soft-tailed woodpeckers from the tropical zones 



^^^*> 



7^--rh,j 



Fio. 21.1. — Di.icrams showing iA) the extensile tongue of Picus from below; <•;«, extensor muscles: /, base of 

 tongue ; xfi, salivary glands : III. Ihyrohyals ; and (/() the tongue bones of Picits from the side ; clii/, ceratohyal ; 

 binj, basihyal ; hr^ ami //r-, thyroliyals. 



of both hemispheres. J'arker regards their ]>alate as the "most embryonic and least 

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

 Cotingida;. The inner edges of the hind jiart of the palatines are greatly expanded 

 posteriorly and bent over so as to form two jiost-palatal flanges, as in the Cotingida? 

 and allies, as well as in the lyre-bird (^fenwa). Of Pioimmis, Professor Parker 

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

 helps to lead the imagination down to extinct types in which the charactei-s of the 

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

 form, — a form and a type only a step or two above the raft-breasted ostrich tribe." 



The great antiquity of the piculets, as the Picumnin.'e are sometimes called, is also 

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

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

 and one, Vcrreai(xia africana, hails from western Africa. 



Externally those birds differ from the other wood|iecker8 chiefly in their diminu- 

 tive size, and the structure of the tail, which is short and comi>osed of normal, that is. 



