1921] Wheeler: Some Social Beetles 111 



to witness this performance as the beetles never exhibited it 

 after the petioles were cut open. I am inclined to believe that 

 the feces are not simply voided in the spaces between the food- 

 grooves but actually built up with the aid of the mouthparts. 

 This seems to be clearly indicated by the circular wall around 

 the entrances (Fig. 11). Perhaps the larvse have quite as much 

 to do with the construction of the ridges as the beetles. 



4. — Concluding Remarks On the Behavior of the 

 Social Silvanids 



All modern observers of insects have been deeply impressed 

 by the highly mechanized character of their behavior, but it is 

 equally true that those who have most closely studied these 

 organisms both under natural and experimental conditions have 

 failed to find that the behavior of any one of them can be com- 

 pletely reduced to a rigid system of automatic or stereotyped 

 reactions. While the behavior of certain forms such as the 

 larval ant-lion, according to Doflein (1916) or the larval worm- 

 lion (Vermileo), as shown by my unpublished studies, seems to 

 consist almost entirely of a small number of reflexes, the behavior 

 of other insects, such as the solitary wasps, termites and social 

 Hymenoptera, often exhibits considerable plasticity, modifiability 

 or adaptability. Between these extremes we find the majority 

 of insects with a certain modicum of the latter type of behavior. 

 To this group we may assign the social Silvanids. The interpre- 

 tation of their various activities necessarily involves some refer- 

 ence to the behavior of insects in general and the assumption 

 of a definite attitude towards certain intricate and much dis- 

 cussed questions. The limitations of space compel me, therefore, 

 either to leave the whole matter unconsidered or to treat it in a 

 very brief and sketchy manner. I prefer to adopt the latter 

 course. 



The fashion which required one to explain as much as 

 possible of the behavior of an insect in terms of tropisms, or 

 taxes, and measured the value of one's work by the success 

 achieved in the endeavor, seems to be rapidly passing. Thirty 

 years ago I followed the fashion with some enthusiasm, but 

 continued observation of the ways of insects has made me very 



