Ant lions are ferocious predators, but some of them don't have a mouth.
Over evolutionary time, the slit at the front of the mouth cavity has sealed shut in the armored larvae of ant lions that hunt in sand.
With no mouth opening and no way to poop, sand-trapper ant lions minimize their intake of anything indigestible.
However, field experiments reveal that ants can detect and effectively avoid high-density ant lion aggregations (Gotelli 1996).
Collectively, these observations suggest that both space and food may be limiting resources for ant lion larvae.
Larvae were held in plastic dishes (12 cm diameter, 2 cm depth) filled with 270 g of oven-dried sand collected from the ant lion zone.
Dishes were randomly placed on the soil surface in the ant lion zone.
Each cup was buried in the ant lion zone with the lip of the cup flush with the adjacent sand surface.
During July of 1992, I mapped all nest entrances that could be found within and adjacent to the ant lion zone at each site along a 10-15 m transect parallel to each cliff ledge.
For several ant species at the Pugh Canyon site, I estimated the probability of death by introducing foragers into the ant lion zone.
At 6 m intervals, I placed one bait station in the center of the ant lion zone and a parallel station on the forest floor, 2 m beyond the edge of the ant lion zone.
I constructed artificial ant lion patches on the forest floor in order to reveal the biotic and abiotic cues used by ants in avoiding predators.