100 A. S. PEARSE 



one place to another, a third hid itself on the under side of a 

 flower, the remaining two took positions on the tops of flowers 

 in plain view and assumed a w^atchful attitude, apparently 

 seeking prey. Neither of the two latter individuals seemed to 

 be disturbed by the close proximity of bees and seldom changed 

 their positions when approached. 



As a result of these and other similar observations made in 

 the course of different experiments the writer was convinced that 

 the behavior of Misumena is not finely adapted to enable them 

 to escape predaceous hymenopterous insects. The reactions of 

 different individuals apparently depend upon their physiological 

 state. Some (hungry ?) spiders are pugnacious and ready to 

 attack almost anything that approaches, other are secretive 

 and remain in hiding. 



DISCUSSION OF EXPERIMENTS 



For the sake of conciseness the relation of the writer's experi- 

 ments to the literature concerning similar investigations has 

 been reserved for discussion at this place. This plan has the 

 additional advantage of bringing all the conclusions together 

 before we pass to the "general considerations" following. The 

 arthropods used for the foregoing experiments will be considered 

 separately. 



The crayfish. — Protective resemblance is common among 

 crustaceans. Beebe ('09) points out a very striking case in the 

 mangrove crabs on Trinidad Island, where a certain species 

 shows a great variety of colors which correspond closely to the 

 roots it frequents. Many crustaceans have been shown to undergo 

 marked color changes which bring about a general correspon- 

 dence with the colors in their environment, and careful studies 

 have been made of these changes in certain Decapods and 

 Mysidaceans by Keeble and Gamble ('00, '04), and in the crayfish 

 by Kent ('01). More recently Franz ('10) has investigated the 

 chromatophores of Pandalus and Crago. All of these investi- 

 gators agree that the color of the background is an important 

 factor in inducing color changes. 



There is evidence that color changes in the skin may be in- 

 fluenced by stimuli acting through the eye and central nervous 

 system (Frohlich, '10; Keeble and Gamble, '04), nevertheless, 



