Caterpillars indeed resemble tempting treats for ants with all those little legs, vibrant colors, and protruding eyes. The majority of caterpillars are protected by their own toxic substances, which is beneficial for monarch caterpillars (and sad for hungry ants). One of these bug larvae will cause an ant to promptly vomit it out in disgust if it is eaten.
Not every caterpillar is as fortunate. Some species are simple prey for hungry ants because they lack toxic compounds. Such an unlucky victim of ant predation is the common larval stage of the black swallowtail butterfly. The ant is one of the most tenacious predators of butterflies despite its small size. Given that it may eliminate a variety of butterflies, the ant is a well-known illustration of biological pest control.
It turns out that its favored food is the Grizzled Skipper Butterfly, which creates vibrations by opening its wings. These movements are rapidly noticed by the ants. This allows them to now eat larger insects like butterflies. Because it is more challenging to catch a fleeing butterfly, making it a weaker and more "immobile" target, most ants choose to attack the caterpillar. Like its older version, the caterpillar emits vibrations that make it easier to trap.
