THE ANTS, BEES, AND WASPS T9 



workers. The males and females are at first winged, and 

 take flight in great numbers into the air on some warm day 

 in spring. At this time fertilization occurs. On their return 

 the males soon die, and the females, stripping off their wings, 

 become the mothers of colonies. The females can be distin- 

 guished from the workers by their larger size and the presence 

 of well-developed ocelli. 



Many other insects, especially beetles, live habitually in the 

 nests of ants, and, in some cases at least, seem to perform some 

 useful function, acting as scavengers, for instance. These 

 cases, like that of the bumblebees and guest-bees, may be 

 cited as illustrations of commensalism (Lat. com ( = cum\ to- 

 gether ; mensa, table), an association of one species of animal 

 with another for support or advantage, but not as a parasite. 



An illustration of cooperation between two different species 

 of animals is shown in certain ants and aphids. The corn-louse 

 ant '(La'sius) collects the eggs and young of a species of aphid 

 (A'plds mai'dis), which attacks the roots of corn in the Middle 

 States, and guards them throughout the winter in subterra- 

 nean burrows, so as to provide a constant supply of " honey- 

 dew." Some ants build a shelter of wood-pulp or mud over 

 colonies of aphids, which are crowded on a branch, from which 

 they derive their nourishment. These aphids are often spoken 

 of as the cows of the ants. In these cases the relation between 

 the ants and aphids is clearly of a more intimate character 

 than the association of the bumblebees and guest-bees; and 

 the advantages are mutual, for while the ants secure a con- 

 stant supply of food, the aphids receive care and a certain 

 amount of protection against their enemies. This association 

 is spoken of as symbiosis (Gr. syn, together ; bios, life). 



An ant found in eastern Asia lives in shelters which it 

 forms on the leaves of trees by fastening the edges of the 

 leaves together. The imagoes have no sticky secretion for 

 this work, but the larvse have glands which furnish such a 



