ADAPTATION 345 



drones may return to the hive with the queen and remain there. 

 Drones may be present in a colony up to the end of the honey 

 flow, after which they are carried off by the workers to some dis- 

 tance from the hive, 100 ft. or more, and left to die. The life of a 

 drone thus extends over a variable number of weeks. The life 

 of the worker is determined by the amount of work it does. 

 When food is abundant, it is actively employed in collecting it 

 and under these conditions lives for about six weeks. With less 

 work the life span is lengthened. The bees which survive the 

 winter are those which emerged in the early autumn. In their 

 case the length of life extends over several months. 



There are also many varieties of such colonial organization 

 among ants, such as Atta, a genus of leaf-cutting ants found in 

 tropical America. A typical colony is made up of a queen, some 

 drones, and numerous sterile females, which in this group are 

 found in three types, known as the maxims, mediums, and minims. 

 As in the case of the honeybee, the function of the queen is to 

 lay eggs, the drones to supply spermatozoa for fertilizing the 

 eggs, and of the workers to rear the young and to provide for the 

 colony generally. The maxims are large in size and have power- 

 ful biting jaws with which they defend the nest. The mediums 

 are smaller and their duties are largely domestic. They bring into 

 the nest small pieces bitten out of a leaf which are handed over 

 to other mediums who thoroughly chew the leaf tissue. The 

 triturated tissue is then taken over by the minims who form it 

 into balls on which a certain fungus (Rozites gongylophora) is 

 cultivated. The fungus is used as food by the entire colony. 



Commensalism. — Commensal animals, literally, are those that 

 eat at the same table. In biology, commensalism refers to an 

 association between two different species of animals partaking 

 of the same food. The benefit of such an association in many 

 known cases seems to be one-sided rather than mutual. A com- 

 mon example of commensalism is found in the association of 

 suckfishes, members of the genus Remora, and sharks. The 

 suckfish has a slender body about 18 in. in length, provided with 

 a peculiar sucking disk on the top of the head, by means of 

 which it attaches itself to the side of the shark's body (Fig. 196). 

 The shark carries the suckfish about and apparently suffers no 

 harm from its passenger; but neither does it benefit. The suck- 

 fish, on the other hand, probably picks up scraps of the shark's 



