398 THE CAXADIAX ENTOMOLOGIST 



The peculiar structure of the ant's aHmentary track was des- 

 cribed in some detail, with its "social" and "individual" stomachs, 

 which enable the insects not only to store their liquid food in the 

 most economical manner but also to distribute it equally among 

 the various members of the colony both larval and adult. For the 

 purpose of illustrating this portion of the lecture more fully, the 

 various adaptions of ants to living in very dry regions, such as 

 deserts, were examined, and it was shown that these insects have 

 evolved four very different methods of circumventing the diffi- 

 culties inseparable from life under conditions that imply a great 

 scarcity of their natural insect food. A certain number of species 

 have exaggerated their primitive predatory instincts and have 

 become rapacious hunters (e.g. the species of Cataglyphis in the 

 North African deserts). Others have taken to storing quantities 

 of liquid food in the crops, or social stomachs of certain workers 

 of the colony for the purpose of tiding over the long droughts 

 (e.g. the honey ants of the South-western States and Australia 

 belonging to the genera Myrmecocystus, Melophorns, Camponolus, 

 Leptomyrmex, etc.). Other species have become agricultural or 

 harvesting ants (the species of Messor, Pogonomyrmex, many 

 species of Meranoplus, Pheidole, Solenopsis, etc.), and have there- 

 fore become addicted to a vegetable diet. These forms store the 

 seeds of various desert plants in their nests. Lastly, a group of 

 American ants, comprising the species of Atta and allied genera, 

 has learned to grow fungi for food on pieces of leaves, caterpillar 

 excrement or other vegetable detritus. Although this habit seems 

 to have originated in the moist woods of South and Central 

 America, several of the species which acquired it were able by its 

 means to invade the deserts of the Mexican plateau and of the 

 South-western States and thus to remain independent of the pre- 

 carious supply of insect food peculiar to those regions. This 

 represents the most specialized stage of ant dietetics. 



The protective instincts of ants, apart from their stinging and 

 biting proclivities, attain their most striking expression in the 

 construction of the nests. The various types of these structures 

 were briefly considered: the small crater nests in the soil, the 

 nests under stones and in wood, the larger mound nests, which 

 are characterized by a superstructure of accumulated vegetable 



