652 Reflexes, Instincts, and Intelligence 



Sphex which has the same habit, Fabre moved the creature a little way off; 

 the wasp came out, brought it to the opening as before, and went within a 

 second time. This was repeated again and again until the patience of the 

 naturalist was exhausted, and the persistent wasp took her booty in after 

 her appropriate fashion. She must place the grasshopper just so close to 

 the doorway, she must then descend and examine the nest, and after that 

 must come out and drag it down. Nothing less than the performance of 

 these acts in a certain order satisfies her impulse. There must be no dis- 

 turbance of the regular method or she refuses to proceed. Again, we see 

 Oxybelus scratching open her nest while on the wing and entering at once 

 with the fly held tightly in her legs. Each way is characteristic of the species 

 .and would be an important part of any definition of the animal based upon 

 its habits. 



"The general style of the nest depends upon instinct. Trypoxylon uses 

 hollow passages in trees, posts, straws, or brick walls; Diodontus ameri- 

 canuSj a member of the same family, always burrows in the ground, as do 

 Bembex, Ammophila, and Sphex. In the case of Trypoxylon the passage 

 may be ready for use or may require more or less preparation; the instinc- 

 tive part is the impulse that impels the insect to use a certain kind of habi- 

 tation. Any one familiar with T. rubrocinctum would never look for their 

 nests in standing stems or under stones; to use Mr. Morgan's test, he would 

 be willing to bet on the general style of the dwelling-place. All of these 

 acts are similarly performed by individuals of the same sex and race, not in 

 circumstantial detail but quite in the same way in a broad sense. Variation 

 is always present, but the tendency to depart from a certain type is not 

 excessive. In the drawing of the nest of Cerceris nigrescens the burrow is 

 seen to be tortuous, this style of work being common to many species in 

 the genus and very characteristic. No Sphex nor Ammophila constructs 

 any such tunnel. The adherence of all the members of a species to a certain 

 style of architecture is, then, due to instinct. 



"The spinning of the cocoon, in those species in which the larva is pro- 

 tected in this manner, and its shape, are instinctive. We find that closely 

 allied species in the same genus make very different cocoons, as is seen in 

 T. rubrocinctum and T. bidentatum. Some wasps never cover themselves 

 with a cocoon, as in the Australian species Alastor eriurgus and Abispa 

 splendida. It is a well-known fact that silkworms sometimes omit the spin- 

 ning of a cocoon; but this does not affect the argument, since the descend- 

 ants of these individuals make the characteristic covering. Such cases are 

 probably due to individual variation or perhaps to atavism, this throwing 

 back being not uncommon among forms that are well known. 



"Not all of the instinctive facts here enumerated are displayed by each 

 species studied, although as a general proposition they are common to most 



