No. 629] HABITAT BESPONSES OF WATEB-STRIDEB 495 



proved to be lacking in definiteness, precision, and in 

 direction of response. Their locomotor movements were 

 very awkward and they stumbled along the route in a 

 very blundering fashion. Their method, if it can be 

 called such, of reaching the water seemed to be entirely 

 one of chance. They might blunder on to a pool of water 

 in the vicinity or they might not. They frequently took 

 the wrong direction and made many mistakes. A better 

 way, perhaps, to express my thought, is to state that these 

 gerrids pass from the site of a former pool to another 

 body of water by a blundering method of trial and error. 

 As Holmes (1916, p. 158) w^ell has said: 



The method is round about and expensive, but it is better than 

 nothing. It is Nature's way of Wundering into success. 



It is not improbable that the method of trial and error 

 forms a large part of the habitat responses of arthropods. 

 It is certainly true that a number of writers have been 

 impressed with the prevalence of behavior of such a 

 character among tlie members of this groui). Among 

 others, this is evident from the work of Bohn (1903) in 

 connection with hermit crabs. Holmes (1905, p. 106) in 

 describing the behavior of the blow-fly larva, ^vith refer- 

 ence to light, makes the following statement : 



Writing of the trial and error method in the conduct 

 of lower animals, Holmes (1905, p. 108) states that: 



The lives of most insects, crustaceans, . . . and host? of h)wer inver- 

 tebrate forms, . . . show an amount of busy ex])l..ralion (liat in many 

 cases far exceeds tliat made by any higher ai)iiiial. 

 In this connection the following geiiei'al statements are 

 of great interest, as tliey show the imj>ortance that is 

 now attached to sucli a method of conduct among inverte- 

 brates: Holmes (1!)0.-). ])]>. 107, lOS) points out that: 



