254 THE INFANCY OF ANIMALS 



a doorway guarded against invasion from without by 

 an ingenious chevaux-de-frise ! The cocoon of the " slug- 

 caterpillar " is hardly less remarkable, since it is furnished 

 with a movable lid. 



The extraordinary instincts of the caterpillars of the 

 American hog-moth deserve particular notice here. 

 These larvs, while they spin their cocoons in the full light 

 of day, yet contrive so artfully to blend them with their 

 surroundings as to make them practically invisible. To 

 attain their ends they are often obliged to resort to a 

 device which exhibits the high-water mark of instinctive 

 sagacity. If the caterpillar cannot find at hand a suitable 

 place in which to weave its cocoon, it frequently makes 

 for itself more satisfactory surroundings by killing the 

 leaves, upon which, after they have become dry and 

 brown in colour, it places its cocoon. 



To secure the desired dry leaves, when these are not 

 already to hand, several caterpillars unite together, and, 

 selecting a long and vigorous immature shoot or leader 

 of the orange tree, they kill it by cutting into its base 

 until it wilts and bends over. The leaves of a young 

 shoot in drying turn a light tan colour, which harmonises 

 most perfectly with the hairy locks of the caterpillar 

 spinning the cocoon. The latter is, consequently, not 

 easily distinguished even when placed upon the exposed 

 and upturned surface of the leaf. 



The life of a caterpillar, from the human standpoint 

 at any rate, is dull and uneventful enough. And this 

 being so, the closing scenes therein are the more remarkable. 

 Among the higher animals we are accustomed to find 

 complicated actions acquired only after much practice 

 and some parental instruction. But the caterpillar 

 which climbs the stem of its food-plant for the last time, 



