430 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1960 



ment. Colonies, however, fight and rob each other just as do nations 

 of Homo sapiens. 



In describing the behavior of animals, we continually use the term 

 "instinct," though we have no proper definition of the word. ^Vlien 

 members of a species always do the same thing under the same cir- 

 cumstances, it would seem that their performance results from some 

 built-in neuromuscular mechanism activated by a sensory stimulus. 

 Most instincts, however, involve a number of related acts, which should 

 require a complex ready-to-act system of nerve tracts to appropriate 

 muscles, successively activated by sensory stimuli. Such a system has 

 not been demonstrated by neurological studies, but the inheritance of 

 an instinct is understandable only on the assumption that instinct is 

 a function of an inherited physical mechanism. 



Insects unquestionably know how to do nearly all the things they 

 do without learning or former experience. But when we think of a 

 cluster of hive bees building a honeycomb with flakes of wax they pick 

 out of pockets on the undersides of their abdomens, manipulating the 

 wax with their mandibles and constructing perfectly hexagonal cells 

 of two sizes, it is difficult to believe that the bees are provided in ad- 

 vance with neuromuscular mechanisms capable of producing such 

 complex coordinated behavior. On the other hand, it is certain that 

 the workers in a comb-building gang are not guided by reason, since 

 they would not all reason alike and their work would be disordered. 

 We must concede that "instinct" is still a word that needs explaining, 

 though it stands for facts that cannot be denied. "Wliile much 

 analytical experimental work has been done on the nature of instinct 

 in vertebrate animals, the "mental" development of an insect is so dif- 

 ferent from that of a vertebrate, that the nature of instinct in an insect 

 is not to be deduced from that of a rat. Vertebrates are conscious ani- 

 mals; insects give no evidence of having consciousness. Yet it is hard 

 to visualize insects, with all their activities, as mere machines that 

 do not know even that they exist. It is as easy to imagine automobiles 

 driving themselves on a crowded thoroughfare without collisions. 



THE TERMITES 



The termites are insects that have become too familiar to us because 

 of the damage they do to wooden fenceposts, utility poles, and the 

 wooden parts of our houses. They can be very destructive also to 

 books if they gain access to them, not because they have any taste for 

 literature, but because paper is made of wood. Wood, in fact, is the 

 natural food of termites; its chief constituent, cellulose, they digest 

 by means of cellulose-digesting protozoa that flourish in their 

 stomachs. 



Our commonest destructive termites live in the ground, but they 

 are always looking for wood lying on the ground or inserted into it. 



