The Problem of Adaptation 3 



of the outer surface of the tibia is arched over by stiff 

 hairs. The pollen collected from the stamens of flowers 

 is stowed away in this receptacle by means of the other 

 pairs of legs. The structure is unique, and is not found in 

 any other insects except the bees. It is, moreover, present 

 only in the worker bees, and is absent in the queen and the 

 males. 



The preceding cases, in which the adapted parts are used 

 for the ordinary purposes of life of the individual, are not 

 essentially different from the cases in which the organ is 

 used to protect the animal from its enemies. The bad taste 

 of certain insects is supposed to protect them from being 

 eaten by birds. Cases like this of passive protection grade 

 off in turn into those in which, by some reflex or voluntary 

 act, the animal protects itself. The bad-smelling horns of 

 the caterpillar of the black swallow-tailed butterfly (Papilio 

 polyxenes) are thrust out when the animal is touched, and it 

 is believed that they serve to protect the caterpillar from 

 attack. The foetid secretion of the glands of the skunk is 

 believed to serve as a protection to the animal, although the 

 presence of the nauseous odor may lead finally to the exter- 

 mination of the skunk by man. The sting of bees and of 

 wasps serves to protect the individual from attack. The sting 

 was originally an ovipositor, and used in laying the eggs. 

 It has, secondarily, been changed into an organ of offence. 



The special instincts and reflex acts furnish a striking 

 group of adaptations. The building of the spider's web is 

 one of the most remarkable cases of this kind. The con- 

 struction of the web cannot be the result of imitation, since, 

 in many instances, the young are born in the spring of the 

 year following the death of the parents. Each species of 

 spider has its own type of web, and each web has as char- 

 acteristic a form as has the spider itself. It is also important 

 to find that a certain type of web may be characteristic of 

 an entire family of spiders. Since, in many cases, the web 



