46 Papers from the Marine Biological Laboratory at Tortugas. 



After studying the habits of the " walking-stick " one finds that the fore- 

 going expectations for its behavior are minutely carried out, with the single 

 exception of the last mentioned. 



In the following pages I shall discuss the habits of Aplopus and enume- 

 rate the results of a number of experiments conducted to test its responses 

 to various stimuli and changed conditions. Record will also be made of 

 some experiments concerning their mating instincts, in which males were 

 induced to copulate with the amputated abdomen of a female attached to a 

 small stick supported by wire legs. 



The experiments were performed at the Laboratory of Marine Biology 

 of the Carnegie Institution of Washington, Tortugas, Florida, and it is a 

 pleasure to express my thanks to Dr. Alfred G. Mayer, the Director of the 

 Laboratory, for many courtesies extended to me while there, and for the 

 kindly interest he has shown in my work. 



BEHAVIOR OF APLOPUS IN NATURE. 



Aplopus mayeri is a large insect, the females often measuring more than 

 8 inches from the tip of antennae to the tip of abdomen, while for the 

 smaller male 6 inches is an adult length. The male's antennas are longer 

 than those of the female. The male is much more sensitive to stimuli and in 

 nature is the more active of the two. Figures i and 2 of plate i illustrate 

 females and figure 3 shows a male, all reduced to two-thirds natural size. A 

 decided difference in color will be noted between the two females, one being 

 very dark, while the other is a pale gray. A large variety of gradations 

 exist between these two extremes. The males are more or less greenish, but 

 they also vary considerably in color. In some males the abdomen is a rich 

 dark brown, in others a pale drab. The legs in all are darker or lighter 

 shades of green. Such variations are common within the family Phasmidse, 

 all members of which are more or less protectively colored and constructed. 



The young males are brown or grayish, resembling the females in color, 

 and can only be distinguished from them by the absence of the oviscapt and 

 the presence of a prominent organ of intromission on their ventral surfaces 

 near the tip of the abdomen. At maturity, however, the males acquire the 

 adult greenish color and may then be recognized at a glance. The wings of 

 both sexes are rudimentary, but are capable of being raised when the 

 animal is greatly excited, giving to it a lively and agitated appearance. 

 Aplopus has spines and prominences on its body and legs suggesting the 

 slight irregularities on the bark of twigs. 



These insects are found only on their food-plant, Suriana maritima, 

 and on this shrub they are extremely difficult to detect. In color and shape 

 the female resembles closely the stems of small branches. The greenish 

 color of the male conceals it among the leaves, while one may find a close 

 resemblance in size and color between the eggs of Aplopus and the seed of 



