Caterpillars are larval stages of butterflies and moths, known for consuming plant matter to fuel their rapid growth before metamorphosis. While primarily herbivores, the question arises if they ever resort to eating each other.
Primary Food Sources
Most caterpillars are herbivores, consuming plant material for development. Their diet predominantly consists of leaves, but they also eat grasses, flowers, and fruits of specific host plants. Caterpillars obtain the water they need directly from the moist leaves they consume, rather than by drinking. Some caterpillar species are highly specialized, feeding only on one or two particular plant species, such as Monarch caterpillars exclusively consuming milkweed.
When Cannibalism Occurs
While plant matter forms the bulk of their diet, caterpillars can engage in cannibalism under certain conditions. This behavior often arises when primary food sources become scarce, leading to starvation. Overcrowding and high population densities also contribute to cannibalism, increasing competition for resources and inducing stress among individuals.
Caterpillars may also be consumed accidentally during intense feeding, especially when many individuals are present on a single plant. Weaker, injured, or recently molted caterpillars are particularly vulnerable, becoming easy targets for opportunistic feeding. In some instances, caterpillars may eat eggs, other larvae, or even pupae, even when plant food is available, possibly due to the nutritional content derived from the same host plant they consume.
Environmental and Species-Specific Triggers
Beyond immediate food shortages, specific environmental factors and inherent traits can increase the likelihood of cannibalism among caterpillars. Plants themselves can induce this behavior as a defense mechanism; when attacked, some plants release chemicals like methyl jasmonate, which make their foliage less appealing or even foul-tasting to caterpillars. This chemical defense can prompt caterpillars to turn on each other instead of continuing to feed on the plant. Studies show that a higher concentration of these defensive chemicals leads to a quicker onset of cannibalism.
Certain caterpillar species exhibit a natural predisposition towards cannibalism, even in less extreme circumstances. Cloudless Sulphur, Pipevine Swallowtail, and Gold Rim Swallowtail caterpillars are known for this tendency, sometimes attacking others even on large host plants. Molting is a particularly vulnerable time for caterpillars as they shed their old exoskeleton to grow. During this period, their new skin is soft and they are immobile, making them susceptible to being consumed by other caterpillars.