4 Psyche [March- June 
thread for racial survival lies in the avoidance of contact by the 
egg with the wet wall of the cell. All predacious wasps seem par- 
ticular as to the site of attachment of the egg, usually choosing the 
upper surface of the prey; or, if the egg is laid on the ground, as 
in the case of certain fly-catchers that feed the prey from day to 
day, a pebble is chosen to receive the egg. Of interest in this con- 
nection is the “ transitional” habit of Rhaphiglossa zethoides , a 
solitary Vespid which attaches its egg, not by a thread, but by an 
elongated end in such a way that the egg projects away from the 
wall at an angle of about 45 0 . This wasp is of further phylogenetic 
interest in the use of both wood fiber, after the manner of the 
social wasps, and mud, which solitary Sphecina as well as Vespina 
usually employ. 
Summary. The act of oviposition of Odynerus rugosus is here 
described and the probable function of the suspensory thread of 
the Eumenid egg is discussed. 
