THE EEAD. H 



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

 following the same authority, the large workers of 

 Camponotus 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 fuliginosus, 200 ; in Tapinoma erra- 

 ticum, 100; in Plagiolepis pygm(ca, 70 to 80; in 

 Lasius jiavus, about 80 ; in Bothriomyrmex meri^ 

 dionalisj 55 ; in Strongylognathus testaceus, Stenamma 

 Weshvoodii, and Tetramorium ccespitum, about 45 ; 

 in Pheidole fallidula, about 30 ; Myrmedna La- 

 treillei, 15 ; Solenopsis fugax, 6 to 9 ; while in Ponei^a 

 contracia 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 insect 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. 



