The catalpa worm, or Catawba worm, is the larval stage of the Catalpa Sphinx Moth (Ceratomia catalpae), a species native to the eastern United States. This caterpillar is known for its voracious appetite for the leaves of its host tree and is highly valued, making its seasonal availability a frequent inquiry. Understanding when these insects emerge requires looking closely at the moth’s life cycle and how it responds to annual shifts in temperature and geography.
Identifying the Catalpa Worm and Its Host Tree
The Catalpa worm is a distinctive caterpillar that can grow up to three inches long before pupating. It is the only sphinx moth species to feed on the catalpa tree. Newly hatched larvae are pale white with black spots, but they develop striking coloration as they mature. Mature caterpillars are usually dark, mostly black, with a broad yellow or greenish stripe along the side.
A stiff, black horn, or spike, protrudes from the rear end of the abdomen, a characteristic shared with other sphinx moth caterpillars. The worm’s existence is entirely dependent on its host plant, the Catalpa tree, which includes both the Northern (Catalpa speciosa) and Southern (Catalpa bignonioides) species. Without the leaves of this specific tree for food, the caterpillar cannot complete its development.
Seasonal Appearance and Multiple Generations
The appearance of the Catalpa worm is not a single annual event but a series of emergences, or “broods,” occurring throughout the warm season. The timing and number of these generations depend directly on the regional climate and latitude. In northern areas, the Catalpa Sphinx Moth may produce only a single generation per year.
Further south, the extended warm season allows for multiple, overlapping broods, with up to five generations occurring in deep southern states. The first generation of larvae typically becomes noticeable in late spring or early summer (May or June), as the adult moths emerge after the host trees have fully leafed out. Subsequent generations develop rapidly over the summer, with the entire life cycle sometimes taking only six weeks from egg to adult.
The population often peaks in late summer, around August and September, as the weather remains consistently warm. Because the generations frequently overlap, caterpillars of different sizes can be found on a single tree throughout the summer and fall. The most abundant numbers are present during the mid-to-late summer months.
Progression Through the Life Cycle
The caterpillar stage is one part of a complete four-stage life cycle. The process begins when the adult moth, emerging after overwintering, lays large masses of 100 to 1,000 eggs on the underside of the host tree’s leaves. These eggs typically hatch within five to seven days, giving rise to the young larvae.
The larval stage lasts for about three weeks, during which the caterpillar feeds voraciously and molts several times, growing significantly in size. Once fully grown, the larva enters a “wandering” phase, crawling down the tree and burrowing a few inches into the soil beneath the host tree. There, it pupates in a chamber without spinning a cocoon, transforming into a spindle-shaped pupa.
For the summer generations, the adult moth emerges from the pupa in about two weeks to begin the cycle anew. The pupae of the final generation in the fall remain dormant in the soil throughout the winter. This overwintering stage dictates the timing of the first emergence of adult moths the following spring.
Why People Seek Out Catalpa Worms
The primary reason people seek out the Catalpa worm is its reputation as exceptional natural fishing bait. Anglers consider the caterpillars irresistible to freshwater fish, particularly channel catfish, bass, and bream. The worms exude a distinctive, potent scent when hooked, which disperses in the water and attracts fish effectively.
This value as bait has led generations of fishermen to monitor local Catalpa trees for signs of feeding, often skeletonized leaves. The worms are also tough-skinned, meaning a single caterpillar can often stay on the hook long enough to catch multiple fish. High demand has led to the commercial preservation of the worms, which can be flash-frozen and saved for use during the off-season.