THE HEAD. 11 



they differ also in the number of facets. Thus, again 

 following the same authority, the large workers of 

 CcLTiiponotus ligniperdus have 500, the smaller ones 

 only 450; while in the Harvesting ant (^Atta barbara) 

 the contrast is even greater, the large specimens 

 having 230, the small ones only from 80 to 90. The 

 ordinary workers have in Polyergus rufescens about 

 400 ; in Lasius fuliginosusj 200; in Tapinoma erra- 

 ticum, 100; in Plagiolepis pygmcea, 70 to 80; in 

 Lasius fiavus, about 80 ; in Bothriomynnex 7neri- 

 dionalis, 55; in Strongylognathus testaceuSyStenamma 

 Weshvoodii, and Tetramorium ccespituvi, about 45 ; 

 in Pheidole pcdlidula, about 30 ; Myrinecina La- 

 treillei, 15 ; Solenopsis fugax, 6 to 9 ; while in Ponera 

 contracta there are only from 1 to 5 ; in Eciton only 1 ; 

 and in Typhlopone the eyes are altogether wanting. 



The number of facets seems to increase rather with 

 the size of the species than with the power of vision. 



The ocelli are never more than three in number, 

 disposed in a triangle with the apex in front. Some- 

 times the anterior ocellus alone is present. In some 

 species the workers are altogether without ocelli, which, 

 however, are always present in the queens and in the 

 males. 



The mouth parts are the labrum, or upper lip ; the 

 first pair of jaws or mandibles ; the second pair of jaws 

 or maxillae, which are provided with a pair of palpi, 

 or feelers ; and the lower lip, or labium, also bearing 

 a pair of palpi. 



