412 BIOLOGIC RELATIONS BETWEEN PLANTS AND ANTS. 



attraction. Upon the head of an ant are borne sense organs — com- 

 pound and simple eyes, organs apparently olfactory in character, 

 antenna?, and buccal organs. On either side of the buccal opening are 

 two large chitiuous pieces, triangular in shape, articulated so that they 

 can be moved apart or toward each other in a horizontal direction like 

 the two jaws of a pinchers, the surfaces in contact being usually cut like 

 a saw. These mandibles have a most important office, serving both as 

 a weapon and as a tool. They are, in fact, used as scissors for cutting, 

 as pinchers for dragging or tearing, as a trowel is in temperiug and lay- 

 ing on mortar, as a shovel for removing excavated matter. It might 

 almost be said that the only use for which they are absolutely unfitted 

 is that of mastication of food. Below and behind them are found the 

 maxillae, formed by three coarticulated pieces, movable, membranous 

 in character, bearing on their surfaces several rows of hairs and gus- 

 tatory papillae. Like the mandibles, they can not serve in mastication, 

 but they assist the lips and the palpi in the recognition and seizure of 

 food. The maxilla? bear the maxillary palpi, composed of from one to 

 six pieces, organs especially tactile. The labrum, usually concealed 

 under the epistoma, forms the anterior wall of the buccal opening. It 

 is a flattened piece of variable form, often bilobate, capable of move- 

 ment from behind forward in a horizontal plane. The lower lip forms 

 the floor of the mouth and carries the ligula, an extensible piece which, 

 because of its mobility, may be used for lapping or licking up fluids. 

 The rows of gustatory papilla? that it carries in front and behind are 

 the principal seat of the sense of taste. On each side of the lower lip 

 are inserted the labial palpi, usually smaller than the maxillary palpi, 

 formed of from one to four pieces. These also are tactile organs. 

 According to Forel the mandibles are never used for eating, The most 

 attentive observations confirm this, and the disproportion between the 

 mandibles and the maxilla? makes it evident. The mandibles remain 

 closed and immovable while the ant is eating. The mouth is usually 

 closed by the labrum, which is turned over it, downward and backward, 

 covering entirely the anterior part of the maxilla? and of the lower lip. 

 When the ant wishes to eat it makes a complex movement of the 

 pharynx which pushes forward the ligula, together with the neighbor- 

 ing parts, raising the labrum like a lid. The maxilla? are too short and 

 too weak to crush a solid; they can only draw into the mouth a liquid 

 or semisolid. It is the ligula or tongue which is most used by ants 

 when they eat, and, according to the apt expression of Lespes, they 

 use it as a dog does when he laps. When the ants are dealing with a 

 solid body inclosing a liquid they first tear it with their mandibles and 

 then lap up its contents. The buccal apparatus can, then, be used for 

 scraping, cutting, and licking. 



Mention should be made of the apparatus for the production of venom. 

 This is situated on the posterior part of the abdomen and, as we shall 

 hereafter see, may render to plants, the friends of our insects, certain 



