Missing comment in Ants model

[ToonTalk]

to look-for-food ;; turtle procedure
if food > 0
[ set color orange + 1 ;; pick up food
set food food - 1 ;; and reduce the food source
rt 180 ;; and turn around
stop ]
;; go in the direction where the chemical smell is strongest
if (chemical >= 0.05) and (chemical < 2)
[ uphill-chemical ]
end

The 'and (chemical < 2)' part of the conditional really should be explained. It is contrary to the comment and the description in the Info tab. I assume its purpose is to prevent those looking from food from following those returning to the nest since that is where there is lots of fresh (yet to be evaporated) pheromone.

I tried to find some explanation as to how real ants avoid this problem without any luck.