110 Chapter III. 



on mechanical automatism nor on individual reflec- 

 tion of the animal, but on the suitable disposition of 

 its sensitive cognition and appetite. 



True, the plasticity of the building instinct is 

 greater with the sanguineas than with their allied 

 species ; yet even the latter sometimes perform actions 

 that go to prove clearly, that the nest-building instinct 

 in ants is not blind mechanism, but is suitably modified 

 by their sensitive cognition. I observed a striking 

 instance of this kind in the summer of 1898 at Lipp- 

 springe in Westphalia. In a growth of young fir-trees 

 near the so-called Fisherman's hut there lay a small 

 heap of old pieces of tar-paper. This treasure had 

 been discovered by some Formica truncicola NyL, which 

 had their nest at a distance of 64 m. in a fir-plantation 

 on the other side of a broad, sandy road. Their nest 

 was a normal truncicola nest, a hill of fir-needles and 

 earth, built around a fir sapling. Now, the ants were 

 better pleased with the newly discovered place under 

 the tar-paper, than with their original nest, therefore 

 they moved over, bag and baggage ; and the moving 

 lasted several weeks. The tar-paper afforded them in 

 a far higher degree the advantages usually derived 

 from their surface domes called ant-hills, for under 

 the layer of tar-paper warmed by the rays of the sun 

 there was a uniformly higher temperature and, at the 

 same time, an effectual shelter against the rain. There- 

 fore they established their nest under the tar-paper 

 without surmounting it by a hill. When I returned 

 to Lippspringe at the end of May, 1899, the truncicola 

 nest was still under the tar-paper, no indications of 

 any building being visible above ground. Their former 



