2 WASP STUDIES AFIELD 



perfected nervous and muscular organization and are cer- 

 tainly less beautifully formed and colored. Second, this 

 unusual physical endowment is correlated, as would be ex- 

 pected, with extraordinary industries, or behavior. Cer- 

 tainly, with the single exception of the social Hymenoptera 

 and the Termites, no insects show such a range of activi- 

 ties as the solitary wasps. Third, they are the lineal de- 

 scendants of forms which gave rise to the social Hymenop- 

 tera. This seems to be so evident that Handlirsch actually 

 derives the bees from the Sphegid, the social wasps from 

 the Eumenid and the ants from the Scoliid wasps, and 

 Roubaud has recently been able to detect in the genera Syna>- 

 gris and .Belonogaster of the Belgian Congo a most inter- 

 esting series of behavioristic transitions between the soli- 

 tary and social wasps. And fourth, the ancestry of the 

 solitary species themselves presents an interesting, though 

 more debatable problem, owing to the fact that the group 

 appears fully developed, at least so far as the families Mutil- 

 lidae and Scoliidae are concerned, in the Baltic Amber of 

 lower Tertiary age. Although no species have been found 

 in older geological formations we must suppose, neverthe- 

 less, that the group goes back to the Cretaceous and prob- 

 ably even to the Jurassic or Triassic. Hence the evolution 

 of the solitary wasps has extended over a period of at least 

 four to six million years. We are not, therefore, greatly 

 surprised to find that they exhibit such a diversity of habits, 

 especially when we remember that the whole mammalian 

 class, man, of course, included, has had a shorter evolution. 

 There is another peculiarity of the solitary wasps which 

 is connected with their geological origin and history. The 

 authors of this book repeatedly call attention, especially in 

 their account of the Bembicids (Chapter I), to the fact 

 that these insects are very strongly attached to their nesting 

 sites and stick to them generation after generation. Such 



