100 PROC. ENT. SOC. WASH., VOL. 21, NO. 5, MAY, 1919 



the social bees and wasps, the termites and the ants -"adaptive 

 plasticity attains its richest and boldest expression in the ants." 



Termites are soft bodied and often blind (degeneracy.) Un- 

 like the ants, they are not dominant insects, despite the fact 

 that they overrun or rather "underrun" certain tropical countries 

 where they are numerous and their damage is great. Haviland 

 (1902) states that ''Their chief means of defense is their power 

 of burrowing and building," "Long legs" (longer 



than abdomen) "and long antennae go with much walking and 

 foraging" -Constrictotermes Holmg. (Eutermes). In species of 

 this genus in the southwestern portion of the United States, 

 the workers and nasuti are also pigmented and wander about 

 above ground. The pigment is developed as the result of light 

 stimulus in species that come above ground into the sunlight. 

 The worker is larger than the nasutus. Usually soldiers are the 

 larger caste. "soldiers with short stout legs belong 



to species sluggish in their movements, and which venture but 

 little from home." In soldiers of Kalotermes the hind femora 

 are short and stout but in the closely related genus Neotermes 

 Holmg. they are more slender and longer. Species of Kalotermes 

 and Neotermes have similar habits and these structural varia- 

 tions can not, with our present knowledge, be correlated or ex- 

 plained as adaptions to their surroundings or as modifications 

 arising from the formation of new habits, due to changed environ- 

 ment. 



The peculiar cavate heads of the soldier caste in species of 

 Cryptotermes Bks. might be explained as an adaptation for block- 

 ing the passing of ants or other marauding predators through the 

 narrow tunnels in the wood interconnecting the board chambers 

 of the colonies. It is more likely that this type of head is a chance 

 variation which has proved useful and has hence survived, for 

 variations, if useless or injurious, often disappear but not always ; 

 adaptations have not yet been proved to be the result of use and 

 disuse. 



Swarming. 



In the semi-arid, sections of the country, such as in certain 

 portions of the southwestern states, on the prairies and great 

 plains, termites usually swarm after a rainfall or during a light 

 drizzle, as is characteristic of many tropical termites. This is 

 an adaptive habit, probably due to the fact that the ground 

 is dry and hard and, unless the swarm occurred just after or 

 during a rain, the termites could not establish or would have 

 great difficulty in establishing new colonies. These conditions 

 of soil do not prevail in the more humid eastern portions of the 



