246 ANIMAL AGGREGATIONS 



wards from the original center, the circle becomes wider, and sooner 

 or later the enemy slips in between the defenses and secures a 

 victim. According to my observations, however, the circle is not 

 broken naturally until the larvae are full grown, in which case the 

 loss of one or two individuals does not signify, for before the bug 

 has digested his meal, the rest of the brood enter the pupal stage 

 and so escape." 



These observations bring us back again to the familiar biological 

 level of the struggle for existence between predators and their prey. 

 They are given here because it frequently appears that such masses 

 of feeding larvae are more at the mercy of their enemies than if 

 they fed alone, unless they have developed means of detecting the 

 approach of enemies and transmitting the information through the 

 mass or unless they have developed effective means of active group 

 defense like that of the soldier caste of termites and ants. 



