NEUTER INSECTS. 221 



munities only one queen is permitted to develop, while the remain- 

 ing females continue sterile, and become adapted to working duties. 

 Among the ants numerous queens develop, but each surviving queen 

 usually becomes the mother of a separate community, in which the ster- 

 ile females are adapted to two or more distinct duties. The problem 

 of the males is a singular one. Among bees and ants they are never 

 checked at the worker stage, but develop to become a possible burden 

 on the community. Here among the bees a second remarkable in- 

 stance of intelligent selection is displayed. The males are suffered to 

 live as long as food is abundant, but are mercilessly stung to death as 

 soon as there is danger of lack of food. In ant communities natural 

 selection disposes of the surj^lus males. Their life-power is reduced 

 to that required for the nuptial flight, and they die as soon as their 

 one necessary duty is performed. 



Among the termites, or white ants, we find an interesting ex- 

 tension of this principle. Here restriction applies to both sexes, the 

 workers and soldiers being immature males and females. Some writ- 

 ers, indeed, hold that they are of no sex, but have been checked in 

 development at the larval stage, before sexual differentiation began. 

 And a male as well as a female survives to start the new community, 

 each nest having its so-called king and queen. In polyp colonies we 

 find the same thing in a less developed stage. Each sexual individual 

 is hermaphrodite, and the king and queen powers exist in a single 

 form. In the Sipho7iophora, or floating hydrozoan colonies, the partly 

 developed forms are adapted to four distinct duties. Some of them 

 become contracting bells, and serve for locomotion ; others become 

 stomachal tubes, and digest the food of the colony ; others are ten- 

 tacles, or food-catchers ; and others are simply covering or protective 

 pieces ; yet in all of them the Medusa type can occasionally be recog- 

 nized. 



It may be well to point out here that a similar division of duties 

 exists in all the higher members of the vegetable kingdom. Each tree 

 is a colony, the product of buds arising in a common stem, and is thus 

 closely analogous to a polyp colony. The analogy goes further — there 

 is a division of duties among the members of the tree colony. Some 

 of these members attain full development and become hermaphrodite 

 sexual individuals. The others are restricted in development, and be- 

 come adapted to several distinct duties. Thus, two distinct nutritive 

 forms appear, the leaf-bearing individual and the root individual. 

 But greatly restricted protective forms occasionally appear, such as 

 the thorn, whose development is on a level with that of the covering- 

 piece in a polyp colony. Other illustrations of this principle of restric- 

 tion of development and division of duties might be given, but we must 

 go on to consider its significance. 



If we consider any of the lower animal forms, it will quickly appear 

 that structural development is checked more or less completely during 



