132 HVMENOPTERA 



greatly in the family : and the Amblyoponides du not differ m 

 a marked manner from the Scoliidae in fossorial Hymenoptera. 



The arrangement of the parts of the mouth is remarkable, 

 and results in leaving the mandibles quite free and unconnected 

 with the other trophi ; the mouth itself is, except during feeding, 



closed completely 

 by the lower lip 

 and maxilla assum- 

 ing an ascending 

 vertical direction, 

 while the upper 



FlQ. 54. — Front of head of Din02}onera grandis. i j„ hand's down 



A, Mouth closed ; B, opeu. ^ ^ 



and overlaps the 

 lower lip, being closely applied to it ; so that in Ponerides 

 the palpi, except the apices of the maxillary pair, are enclosed 

 between the upper and lower lips (Fig. 54, A). In Cryptocerini 

 the palpi are not covered by the closed lips, but are protected by 

 being placed in chinks at the outsides of the parts closing the 

 mouth. The mandibles of ants can thus be used in the freest 

 manner without the other parts of the mouth being opened or even 

 moved. The mandibles close transversely over the rest of the 

 mouth, and when shut are very firmly locked. There are, 

 however, some ants in which the lips remain in the position 

 usual in mandibulate Insects. 



The antennae, except in the males of some species, have a 

 long basal joint and are abruptly elbowed at its extremity. The 

 eyes and ocelli vary excessively, and may be totally absent or 

 very highly developed in the same species. The winged forms 

 are, however, never blind. The size of the head varies extremely 

 in the same species ; it is frequently very small in the males, 

 and largest in the workers. In some ants the worker -caste 

 consists of large-headed and small-headed individuals ; the former 

 are called soldiers, and it has been supposed that some of them 

 may act the part of superior officers to the others. It should be 

 clearly understood that there is no definite distinction between 

 soldiers and workers ; so that in this respect they are widely 

 different from Termites. 



The complex mass forming the thorax is subject to great 

 change of structure in the same species, according as the indi- 

 viduals are winged or wingless. The sutures between the dorsal 



