HABITS, REACTIONS AND MATING INSTINCTS OF THE " WALKING- 

 STICK." APLOPUS MAYERI. 



By Charles R. Stockard. 



An investigation of the behavior of a protectively adapted insect is im- 

 portant to show definitely whether the actions of such an animal are co- 

 ordinated with its protective structure. If an insect such as the " v/alking- 

 stick," which forms the subject of the present discussion, was found to 

 move about briskly on exposed portions of the plant on which it lives, and 

 to show other habits which might attract the attention of enemies in spite 

 of its apparent resemblance to the stems and leafy parts of the plant, then, 

 notwithstanding this resemblance, it would scarcely be as well protected 

 as other insects showing no such resemblance but remaining still and con- 

 cealed among the leaves and branches of the shrub. It is clear to all ob- 

 servers that the behavior of an animal is almost if not quite as important as 

 its structure in determining whether or not the animal is truly protectively 

 adapted to its surroundings. 



With the above as a premise, we may ask what would be the theoretical 

 expectation for protective behavior of such an insect as Aplopus. Since 

 movement attracts the attention of birds and other enemies almost or quite 

 as readily as conspicuous appearance, we should first expect this insect to 

 remain perfectly motionless during the day, while it may be seen, and to 

 move at night ; in other words, nocturnal habits would be ideal for its 

 protection. Aplopus is unable to fly or leap ; thus its most effective means 

 of escape would be to drop bodily from a position when touched, and become 

 lost by falling and alighting among the lower branches of the bush, where it 

 might remain motionless and concealed. When moving from place to place 

 it would attract less attention should it move slowly, and the extreme per- 

 fection of movement would be to vibrate from side to side as it progressed, 

 as a twig swings in a light breeze. The male is colored with more green 

 than the female; therefore, he may move among the leaves to better advan- 

 tage and she will be less conspicuous on the larger brown stems. Lastly, 

 since these insects vary greatly in color, as do most protectively colored ani- 

 mals, we might expect, for instance, that light-gray females would rest on 

 the lighter-colored stems, while the dark-brown type would be found on 

 darker stems. 



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