The Catalpa worm (catawba worm) is the larval stage of the Ceratomia catalpae insect, belonging to the Sphingidae family of moths. This caterpillar is a type of hornworm, identifiable by a stiff, black spine near the end of its abdomen. It feeds exclusively on the leaves of the Catalpa tree, which gives it its common name. After gorging itself on foliage, the Catalpa worm undergoes complete metamorphosis, transforming into the Catalpa Sphinx Moth.
The Adult Form: Catalpa Sphinx Moth
The adult Catalpa Sphinx Moth is a large insect classified as a hawk moth or sphinx moth, possessing a robust, spindle-shaped body. It exhibits camouflage coloration, typically mottled gray and brown across its wings and body. The wingspan measures between 2.5 to 4 inches, and its forewings are usually yellowish-brown with subtle dark lines and a small gray spot.
Adult Catalpa Sphinx Moths are nocturnal, meaning they are primarily active at night. The adult moth is thought to be non-feeding or only consumes nectar, focusing its short adult life on reproduction. This behavior contrasts sharply with the caterpillar stage, which is a voracious eater.
The Complete Life Cycle
The life cycle begins when the female moth lays large clusters of 100 to 1,000 eggs on the underside of Catalpa leaves. After hatching, the tiny larvae feed gregariously near the egg mass. The caterpillars molt several times as they grow, transitioning from a pale color with black spots to a mature worm up to three inches long, often featuring dark stripes.
After approximately three weeks of heavy feeding, the fully grown caterpillar leaves the tree and burrows into the soil beneath the host tree to begin pupation. The pupa is a brown, spindle-shaped structure without a protective cocoon, where the transformation into the adult moth occurs. This pupal stage allows the insect to overwinter in the soil, especially in northern regions. Adult moths emerge in the spring, with the cycle repeating to produce multiple generations, often two to three, and sometimes up to five in warmer southern climates, between May and October.
Ecological Role and Significance
The Catalpa worm holds a dual role in its ecosystem, acting as both a natural defoliator and a highly valued food source. As a caterpillar, it can strip a Catalpa tree of nearly all its leaves quickly, leading to its classification as an agricultural pest. However, healthy Catalpa trees are resilient, often pushing out a new set of leaves after a defoliation event.
The worm is highly valued by humans as exceptional fishing bait for species like catfish and largemouth bass. Some fishermen intentionally plant Catalpa trees to harvest the worms, which are used fresh or frozen. In its native environment, the worm is preyed upon by natural enemies, including parasitic wasps, such as Cotesia congregata. These wasps lay their eggs inside the caterpillar, which helps regulate the worm population and prevent damage to the host trees.