48 Psyche [April-June 



sucked, plus the various particles collected by the ant by means of 

 the strigils of the fore tibiae from the surfaces of the antennae and 

 other parts of the body and carried into the infrabuccal pocket 

 after being wiped off by the maxillse. Other ants eventually spit out 

 the pellet which is commonly a moulded, subspherical conglomer- 

 ate of diverse particles, such as small pieces of insects, fragments 

 of plant tissue, fungus spores and hyphae, pollen grains, etc., and 

 cast it away as refuse, but the worker nurses of the Pseudomyrm- 

 inse place it as pabulum in the trophothylax of the larva ! 



Even this, however, is not the whole story. An examination of 

 the mouth of the larva reveals a singular structure, evidently used 

 for reducing the food pellet to such a finely divided state that it 

 can, when acted on by the digestive juices of the mesenteron, yield 

 a certain amount of nutriment, which the worker ant could not 

 extract from it while it was in the infrabuccal pocket. This 

 larval structure, which may be called the trophorhinium, consists 

 of two flat, opposable plates, the dorsal and ventral surfaces of the 

 buccal cavity, each furnished with very fine, parallel, transverse 

 striae or welts, which, under a high magnification are seen to be 

 made up of minute chitinous projections or spinules. The ventral 

 usually has more numerous rows of spinules than the dorsal sur- 

 face. The two surfaces are evidently rubbed on one another and 

 thus triturate the substance of the food pellet, only small portions 

 of which are ingested at a time from the trophothylax. In all 

 Pseudomyrmine larvae and in many larvae of the other subfamilies, 

 except the Dorylinae and Cerapachyinae, the trophorhinium is 

 beautifully developed, although in many ants (Ponerinae) it may 

 be used for comminuting parts of insects given directly to the 

 larvae by the workers. A detailed description of the organ and of 

 its extraordinary variations of structure in the various genera of 

 Formicidae is reserved for future publication. 



In its development the trophorhinium bears a strange resem- 

 blance to the stridulatory organs of the petiole and postpetiole of 

 many adult Ponerinae and Myrmicinae. It may, in fact, function 

 also as a stridulatory organ, when the food supply is exhausted, 

 and thus apprise the worker nurses of the larva's hunger. Many 

 ant-larvae, notably those of the Ectatommiine Ponerinae and of 

 most genera of Camponotinae (Formicinae) , also have elaborate but 

 coarser stridulatory surfaces on the mandibles, so that the larva 



