58 
Psyche 
[June 
quired for passing liquid through the calyx and tract is 
provided by the bulb. As the bulb starts its contraction, its 
four canals are sealed off, perhaps imperfectly in the pos- 
terior portion, but at least completely enough to act as a 
valve to prevent most of its contents from flowing back 
into the calyx lumen. As the bulb cavity collapses under 
muscle contraction, the contents are forced back through 
the cylinder and into the midgut. As the muscles relax 
and the cavity expands due to the elasticity of its chitinous 
framework, the canals of the posterior portion communi- 
cate again with the lumen and allow liquid from the anterior 
canal system to pour in. Probably some of the liquid is 
sucked in through the filtering slits of the occlusory tract 
also, but the body of the tract is so extensive and its walls 
so densely covered with hairs that traffic through it must 
be relatively insignificant. A forward flow of liquid from 
the midgut is prevented by the cylinder valve, the thin 
walls of which can collapse under external pressure. 
As we presently understand it, the significance of the 
characteristic elaboration of the dolichoderine-formicine 
proventriculus is that it allows the crop to store large 
amounts of liquid. As previous authors have suggested, it 
regulates the amount of this liquid which passes into the 
midgut and in this way separates the individual supply of 
food from the communal supply. In the concept presented 
here, it is considered that the primary feature of the ad- 
vanced proventriculus is the filter area, while the other 
structures are developed supplementarily. This area acts 
as a plug guarding the midgut, and liquid can be forced 
past it only under pressure from the bulb. As its name 
implies, it also acts as a very thorough filter, and perhaps 
correlated with this is the fact that the midgut wall is so 
constructed as to be able to handle only small amounts of 
pure liquid. 
The calyx of the euformicines represents an extension of 
the occlusory tract which allows a greater filtering area and 
possibly provides a secondary valvular control by its ability 
to collapse and occlude liquid from its lumen. In non- 
euformicine types the calyx is either absent or does not 
function in this capacity, and the occlusory tract is more 
massive. In the section Alloformicinae of Emery (Melo- 
