Circumvention of prey defense by a predator: ant lion vs. ant

The pit-dwelling ant lion Myrmeleon carolinus, although topically sensitive to formic acid, is able to prey on formic acid-spraying ants (Camponotus floridanus). It kills the ants without inducing them to spray, and it sucks out the ant's body contents without puncturing the acid sac. Ordinarily, when Camponotus is attacked it retaliates by simultaneously biting and spraying, but it usually refrains from spraying until it has secured a grip with the mandibles. When Myrmeleon pulls Camponotus into the sand at the bottom of the pit, the ant is seemingly unable to grasp the ant lion and it is killed without being induced to spray. When feeding on the ant, the ant lion sucks up the contents of the nutrient-laden crop. How the ant lion differentiates between crop and acid sac, managing to spare the latter while rupturing the former, remains unknown.