THE HABITS OF FIDDLER-CRABS. 129 



some other arthropods; for example, ants, bees, wasps, and ter- 

 mites. In this they agree with other crustaceans, for altho'jgh 

 this class of animals exhibits an endless variety of structural 

 adaptations suited to various habitats and modes of life, r>one 

 of them has apparently taken advantage of the opportunities 

 offered by a cooperative communal association among mem- 

 bers of the same species (except in some instances in which 

 the male is intimately associated with the female). Although 

 the females of many species carry their eggs and newly hatched 

 young for a time, the association of the young with their mother 

 is nominal, for she never feeds nor cares for them. The 

 struggle for existence is nowhere more apparent than in the 

 midst of a fiddler-crab colony. Each individual jealously guards 

 the area about his o'wti burrow and immediately attacks any 

 invader of this territory. His pugnacity is ever ready to show 

 itself against his fellows that swarm about him and against 

 numerous competitors of other kinds that also seek to eke out 

 an existence from the area he has chosen for his own. 



At Manila, the fiddler's chief competitors for the food on the 

 mud flats are : ( 1 ) two species of Macrophthalmus whose feeding 

 habits and food are very similar to those of the fiddler, but 

 that usually live farther from the shore in the deeper parts of 

 the estuaries and hence overlap the fiddler zone on the lower 

 side only; (2) two burrowing crustaceans, Sesarma bidens De 

 Haan and Thalassina anomala (Herbst), sometimes exceeding 

 the fiddlers in size, that live mostly along the upper side of their 

 zone; and (3) some smaller animals, such as the numerous mud 

 snails, nereid worms, and the less frequent hermit-crabs. In 

 addition to honest competition the fiddler must reckon with some 

 larger animals that seek not his food but him. Among these the 

 snakes, skinks, frogs, toads, and fishes are important. 



The behavior of the fiddler is admirably suited to enable him 

 to gain a livelihood and at the same time escape injury or death 

 from his enemies. His aggressive attitude toward members of 

 his own genus and toward other crabs of similar size keeps 

 enough space clear about his burrow to enable him to sift his 

 simple diet from the mud in comparative safety. Furthermore, 

 the way is thus left clear for retreat to his burrow if danger 

 threatens, and the fiddler is not slow in dodging into his hole 

 as soon as any strange or threatening object moves within his 

 field of vision. His burrow is the center of all his activities, 

 and his association for the place where it is situated is very 

 strong. Fiddlers are protected from night prowlers by their 



