MARC HAL ON CERCERIS ORNATA. 209 



hatclied on tlie fourth day. At other times rather big larvae 

 have been kept for three or four days before they spun their 

 cocoons. Thus we have a minimum of eight days for develop- 

 ment, and we have seen that the bees sometimes dry up in five 

 days. It is then almost certain that the larvae of Cerceris often 

 have to eat bees which are already dead. It would be interest- 

 ing to see if, as the instinct of the wasp becomes more perfect, 

 the time necessary for the development of the larva becomes 

 longer, as Darwin would doubtless have thought probable. 



As has been seen, we are far from finding such masters in the 

 art of paralyzing as Fabre did. Moreover, there is much varia- 

 tion both in method and in results. Are these signs of perfection 

 of instinct? 'No. Cerceris ornata, from the point of view of in- 

 stinct, seems to be a transitory type between the butcher wasp 

 and the paralyzing wasp (speaking, now, only of instinct, and 

 not of the line of descent.) The butcher wasp kills and cuts 

 up its victim, eating what it wants and carrying the rest to 

 the larva. The paralyzing wasp is the one that has no individ- 

 ual interest in its prey, as Spheco or Ammophila. Between 

 these types we may put Cerceris ornata, and Chlorion com- 

 pressimi which provisions its nest with cockroaches from which 

 the wings and legs have been cut off, certain Pompilidae, 

 which, according to Goureau, cut the legs from the spiders 

 which they capture, and PhilantJius apivorus, which, according 

 to Fabre, squeezes the bee to make it give up its honey (after 

 paralyzing it), and many other cases which show various shades 

 of evolution of instinct. 



Errors of Instinct. 



While Cerceris was away hunting, some dry sand was thrown 

 into the nest and the entrance was then stopped with damp sand. 

 She returned laden with prey, and seeing herself forced to re- 

 sume the profession of a miner, abandoned her victim, cleared 

 the entrance, penetrated within, came out again, and flew off in 

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