254 HABITS AND INSTINCTS IN LEPTINOTARSA. 



the others. Although the position assumed is constant within a given species, 

 it varies in different species, as, for example, in rnbicunda, which falls with 

 the appendages held in a rigid position straight out from the body. In the 

 two species, multitccniata and rnbicunda, a point of great interest is presented. 

 In the production of the new species there is rapid change in this protective 

 habit as well as in the morphological characters. Hence it follows that modi- 

 fications in the habit may arise suddenly as well as by selection, and this opens 

 the question as to whether or not the habit itself may not have arisen in the 

 same way. 



While being handled the beetles often assume this attitude for a short time, 

 but if the stimulation be continued they soon cease the attempt to escape 

 through concealment, and begin to struggle vigorously ; hence they do not 

 carry the habit to the extent that has often been described in many insects 

 that they allow themselves to be eaten or mutilated without manifesting a 

 sign of life. I have examined several reputed cases of this kind in the tropics, 

 but for some reason or other when under my observation they did not act as 

 they should according to the published accounts. At any rate, in the genus 

 Leptinotarsa the beetles do not carry the habit to the very evidently injurious 

 extent to which it has been carried by other forms that have been destroyed. 



That the habit is really of use to the species in the genus which possesses it 

 there is not the slightest doubt. In nature I have seen undecimlineata, when 

 approached and examined by a gecko, relax its hold upon the food plant, fall 

 to the ground as if dead, and remain there until it considered that danger had 

 passed, when it would crawl back upon the plant. Of the utility of such an 

 act there can not be the slightest doubt. Of course it might often happen that 

 in falling the beetle would get into a worse predicament than the one from 

 which it sought to escape, but, as far as I can see, there is no possible means 

 of determining this point other than by having a trained observer constantly 

 watch the movements of a beetle throughout its adult life. As regards the 

 selective value of the habit, it seems to me to be small, owing partly to the 

 already existing high degree of protection afforded by warning colors, and 

 quite as much to the fact that an insectivorous animal is keen of eye and does 

 not often miss its mark. When, therefore, one of these beetles happens to be 

 the target, the aim is so true and the attack comes so suddenly that the beetle 

 has an extremely small chance of bringing this protective habit into play. 

 Rarely, as with the gecko, the beetle may have a chance to use the habit to 

 advantage, but such opportunities are few and far between, and hence can not 

 play any appreciable part in the preservation of the species. 



After years of observation of these beetles I find it impossible to regard the 

 nature and purpose of this habit to be that usually attributed to the same reac- 

 tion in other animals. I have described the habit in detail, and have shown 

 that while it does have a certain protective value to the species, this value is 



