Instinct. 885 



animals. ' ' One solitary wasp, sphex flavi pennis, which provisions its 

 nest with small grasshoppers, when it returns to the cell, leaves the vic- 

 tim outside and goes down for a moment to see that all is right. Dur- 

 ing the absence of one, M. Fabre moved the grasshopper a little; out came 

 the sphex, soon found her victim, dragged it to the mouth of the cell, 

 and left it as before. Again and again M. Fabre moved the grasshop- 

 per, but ever} 7 time the sphex did exactly the same thing until M. Fabre 

 was tired out. All the insects of this colony had the same curious 

 habit. But on trying the same experiment with a sphex the following 

 year, after two or three disappointments she learned wisdom by experi- 

 ence and carried the grasshopper directly down into the cell." (Lub- 

 bock, Senses of Animals. ) Another species of sphex, tachytes nigra, 

 which usuall}' "makes its own burrow and stores it with paralyzed 

 prey" for its own larvae, will occasionally take possession of the burrow 

 and provisions of another sphex, and appropriate them to her own pur- 

 pose. There is a caterpillar that usually weaves a little silk web to at- 

 tach the chrysalis to. But if such a caterpillar be placed in a box 

 with a piece of muslin stretched across for a lid, she will omit her web, 

 and attach the chrysalis directly to the muslin. 



The above are examples of instincts modified by intelligence. In 

 most actions, as observed before, we find both of these elements. 



"The larva of a beetle (cionus scrophulariae ), when bred on thescro- 

 phularia, exudes a viscid substance which makes a transparent bladder, 

 within which it undergoes its metamorphosis, but the larva when natur- 

 ally bred, or transported by man onto a verbascum, becomes a burro wer, 

 and undergoes its metamorphosis within a leaf. In the caterpillars of 

 certain moths there are two great classes, those which burrow in the 

 parenchyma of leaves, and those which roll up leaves with consumate 

 skill," } T et they belong to the same species. These cases of contingent 

 instinct show that instincts are reactions against stimulations in the en- 

 vironment, and must differ either intelligently or instinctively when the 

 stimulations differ. Many birds which are quite tame to man in a state 

 of nature, are very wild in countries that are inhabited, showing a 

 change in their instincts by the presence of man. 



Darwin also found a sort of water lizzard which has been driven to 

 live on land by the presence of sharks and other enemies inhabiting the 

 water. It lives on water plants, but remains out of the water as much 

 as possible. When he threw one into the water it scrambled out again, 

 being less afraid of him than its aquatic enemies. 



Edible bird's nests vary greatly in structure. The collocalia, the bird 

 which makes the edible nests, belongs to the same sub-famity with the 

 swift They have salivary glands that secrete a sticky, mucilaginous, 

 brittle substance, by which they fasten together the parts that compose 



