ONE-BANDED DAUBER 421 



tiny opening through the film that encloses it, after which 

 the grub finds its mouth flat upon the spider's abdomen. 



As the pumping spasms continue, each one representing 

 a swallowed mouthful of spider substance, the nursling in- 

 creases very gradually in bulk. A few hours after taking 

 its first draught of food stuff, the egg-film apparently splits 

 along the center of the larva's back, one end of the breach 

 traveling in either direction, exposing the actual skin of the 

 young wasp. The breach spreads like a drop of oil upon 

 water, only much more slowly, but twenty-four hours after 

 the first spasm not a vestige of film remains. It appears to 

 have been absorbed into the larva's body. Under the lens 

 it vanishes slowly before my eyes, yet I cannot see where 

 it goes, and when the process is over I can find no trace of 

 it either on the larva or its spider host. The grub is a living 

 dialyzer through whose delicate skin the egg-film appears 

 to osmose. In other words, I believe that the film is ab- 

 sorbed into the insect's body in minute particles in much the 

 same manner that food passes through the walls of the oeso- 

 phagus to reach the distributing corpuscles. 



It is possible that the larva eats the egg-film, but if so 

 it is drawn into the mouth so gradually and with such skill 

 that it is impossible to detect the operation. Therefore, I 

 suggest that the process may be akin to osmosis '. The action 

 is so gradual, yet so smooth and uninterrupted that I can 

 think of no other way to describe it. 



At first the young wasp feeds only on liquid food. Dur- 

 ing the first few hours of its life its mandibles are of a very 

 rudimentary character, in fact scarcely distinguishable until 

 the grub is a day or more old and are developed gradually 

 to be in readiness later when substantial parts of the spider 

 must be eaten. The fact that at birth the grub possesses no 

 adequate appendages for chewing suggests an interesting 

 question How does the tender creature make the first inci- 

 sion through the mature wall of the spider's abdomen? Per- 

 haps the parent wasp pricks it and uses the minute drop of 



