prote:ctive habits. 253 



is long continued seeks relief therefrom in flight, crawling rapidly to a darker 

 portion of the food plant, usually on the under side of a leaf, where it again 

 assumes a similar pose. Stimulation through noise, unusual odors, or the 

 shaking of the food plant produce exactly the same response. 



During the breeding period the beetles are far less responsive to the above- 

 mentioned stimuli. Frequently they will take no notice of the odors, shaking 

 of the food plant, or noise which would at other times drive them to flight and 

 secretion in the darkest and most secluded spots. At such times the over- 

 powering influence of sexual instinct seems to render them oblivious to all 

 other stimuli. Throughout the entire genus there is little or no variation in 

 this habitat ; and it seems to be one that is inherited, for the beetles display it 

 as soon as they emerge from the ground. The protective value of the habit 

 seems to be relatively slight, for it does not serve to conceal the animals from 

 the enemies that are actively looking for them. Its real use seems rather to 

 be that of momentarily decreasing their conspicuousness so that they may be 

 passed unnoticed by any possible enemy. It also affords them an opportunity 

 to determine better the nature of the disturbing stimulus and the direction 

 from which it comes, and, possibly, also to decide what to do in order to 

 escape from the injurious effects which the cause behind the stimulus might 

 bring to them. At any rate, if the stimulus be long continued, the beetles 

 soon seek more efiicient protection by other means, and these are either con- 

 cealment in some shaded and not easily visible portion of the food plant, 

 usually the under sides of leaves, or by more energetic measures, such as fall- 

 ing to the ground, and there remaining motionless as if dead until the danger 

 is past. The attempt to escape through hiding on the under sides of the 

 leaves shows the simple instinct of fear and the response by seeking safety in 

 flight. The imitation of death is, however, a more complicated instinct, which 

 is developed in some and not in other species, and also to different degrees in 

 the same species. 



When an unsuccessful attempt is made to capture one of these beetles with 

 the fingers or forceps, it almost always relaxes its hold upon the food plant, 

 falls to the ground, and rolls away. It remains perfectly motionless where it 

 stops, with legs, antennae, and all parts of the body closely folded together, 

 and whether it has landed on its back, head, or in a natural position, it does 

 not move until all danger has passed. Even in the most exposed situations 

 the habit is highly efficient as a protection, and in the usual conditions of the 

 habitat of these beetles, where the food plant is surrounded by grass and other 

 low, closely packed vegetation, it is a perfect protective device, as most dili- 

 gent and prolonged search is necessary if one wishes to discover them when 

 thus concealed. 



The position assumed is to a considerable extent a specific characteristic. 

 Oblongata, multitceniata, and decemlineata all likewise draw the appendages 

 close to the body, which is not the death position, either for these species or for 



