Psyche 
[September 
114 
membrane has been found lacking in those species (including a Cam- 
ponotus) of these two subfamilies that have been examined. The 
primitive Myrmeciinae, the proventriculi of which have gaping portals 
through which small particles could presumably pass, do have a mem- 
brane (Waterhouse, 1953). 
% CROP -LUMEN FILLED WITH PARTICLES 
Text fig. 1. Frequency distribution of ants classified according to corundum 
content of their crops. The ants were fed 12 hours earlier on honey laden with 
10/i-corundum powder, and were confined immediately after the meal either in 
isolation (black bars), or together with groups of unfed nestmates (striped 
bars). See text for details. 
One wonders whether, despite the effectiveness of infrabuccal filtra- 
tion, enough detritus sometimes remains in the crop to interfere — 
perhaps only temporarily — with the normal operation of the proven- 
triculus: particles accumulated over the portal clefts might effectively 
