THE HEAD. 11 



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

 following the same authority, the large workers of 

 CaTnponotus Ugniperdus have 500, the smaller ones 

 only 450 ; while in the Harvesting ant {Atta harhara} 

 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 fidiginosus, 200; in Tapinoma erra- 

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

 Lasius Jlavus, about 80 ; in Bothriomyrmex meri- 

 clionaMs, 55 ; in Strongylognathus testaceus, Stenmnma 

 Weshvoodii, and Tetramorium coespitum, about 45 ; 

 in Pheidole pcdlidula, about 30 ; Myrmecina 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. 



