59 8 THE POPULAR SCIENCE MONTHLY. 



The Lanius collurio, an allied bird, uses this method still more 

 frequently. He even prepares a small larder before feasting. 

 One may thus see on a thorny branch spitted side by side Coleop- 

 tera, crickets, grasshoppers, frogs, and even young birds, which 

 he has seized when they were in flight. (Fig. 3.) 



Of all these well-attested facts that which perhaps best shows 

 how animals in certain circumstances may take advantage of a 

 foreign body to utilize the product of the chase is the following, 

 the observation of which is due to Parseval-Deschenes. He fol- 

 lowed during several hours an ant bearing a heavy burden. On 

 arriving at the foot of a little hillock the animal was unable to 

 mount with his load, and abandoned it a very extraordinary fact 

 for one who knows the inconceivable tenacity of insects. The 

 abandonment, therefore, left hope of return. The ant at last met 

 one of his companions, who was also carrying a burden. They 

 stopped, took counsel for an instant, bringing their antennae to- 

 gether, and started for the hillock. The second ant then left his 

 burden, and both together seized a twig and introduced its end 

 beneath the first load which had been abandoned because of 

 its weight. By acting on the free extremity of the twig they 

 were able to use it exactly as a lever, and succeeded almost with- 

 out trouble in passing their booty on to the other side of the little 

 hillock. It seems to me that these ants who invented the lever 

 are worthy of admiration, and that their ingenuity does not yield 

 to our own. 



Animals construct dwellings either to protect themselves from 

 the cold, heat, rain, and other chances of the weather, or to retire 

 to at moments when the search for food does not compel them to 

 be outside and exposed to the attacks of enemies. Some inhabit 

 these refuges permanently ; others only remain there during the 

 winter ; others, again, who live during the rest of the year in the 

 open air, set up dwellings to bring forth their young, or to lay 

 their eggs and rear the offspring. Whatever the object may be 

 for which these retreats are built, they constitute altogether vari- 

 ous manifestations of the same industry, and I will class them, 

 not according to the uses which they are to serve, but according 

 to the amount of art displayed by the architect. 



DWELLINGS FORMED OF COARSELY ENTANGLED MATERIALS. 

 Diurnal birds of prey are the first animals who practice skillfully 

 the twining of materials. Their nests, which have received the 

 name of eyries, are not yet masterpieces of architecture, and re- 

 veal the beginning of the industry which is pushed so far by 

 other birds. Usually situated in wild and inaccessible spots, the 

 young are there in safety when their parents are away on distant 

 expeditions. The abrupt summits of cliffs and the tops of the 

 highest forest trees are the favorite spots chosen by the great 



