Catalpa sphinx

📖Overview

Ceratomia catalpae is a hawk moth (sphinx moth) whose green, often-striped caterpillars are commonly called catalpa worms. The species is well known in eastern North America where catalpa trees (Catalpa spp.) are planted; larvae feed almost exclusively on catalpa leaves and can occur in large numbers. Adults are stout-bodied, nocturnal moths with rapid flight and a typical sphingid shape.

The caterpillar stage is the most visible and economically important life stage because heavy infestations can strip small ornamental catalpa trees. Natural enemies (birds, parasitic wasps and flies) and periodic management usually keep populations in check. Adults do not damage plants and feed little, if at all; they are short-lived and primarily active at dusk and night.

🔍How to identify a catalpa sphinx

Adult moths have the streamlined, tapered wings and robust body typical of sphinx moths. Forewings are gray-brown with wavy darker lines and paler patches; wingspan typically 6.5-9.5 cm. Caterpillars are smooth and hairless with a black horn at the rear (typical of hornworms). Early instars are pale and nearly white; mature larvae are pale yellow-green with a variable amount of black, ranging from rows of black spots along the sides to a broad black stripe down the back. Eggs are small, rounded, and pale green to yellow; pupae are brown, stout, and formed in the soil or leaf litter.

1. Look for smooth yellow-green caterpillars marked with black (a black back stripe or rows of black side spots) and a black rear horn, feeding in groups on catalpa leaves.
2. Adult is a sphinx moth with a 6.5-9.5 cm wingspan and gray-brown forewings with wavy dark lines.
3. Clusters of chewed leaves or noticeably skeletonized catalpa branches during late spring or summer indicate catalpa worms.

Lookalikes

↻Life cycle

1. 🥚

   Egg

   Females lay masses of up to several hundred pale green eggs on the undersides of catalpa leaves. Eggs hatch in a few days to a week depending on temperature.

2. 🐛

   Larva (caterpillar / catalpa worm)

   The caterpillar passes through several instars, growing from a few millimetres to several centimetres. Larvae consume large amounts of catalpa foliage and are the conspicuous, damaging stage.

3. 🫛

   Pupa

   Mature caterpillars leave the tree and pupate in the soil or leaf litter, forming a brown, obtect pupa that overwinters or develops to an adult the same season.

4. 🦋

   Adult (moth)

   Adults emerge from pupae, mate, and females lay eggs on catalpa. Adults are nocturnal and are attracted to lights.

🍃Diet and predators

🌱Effect on plants and gardens

Larvae feed almost exclusively on catalpa (Catalpa spp.) leaves. Heavy infestations can strip young or small trees of their foliage; mature trees typically sprout new leaves and usually recover.

How to get rid of catalpa sphinxes

Usually no treatment is needed: healthy catalpas regrow leaves and parasitic wasps often collapse outbreaks (leave caterpillars carrying white wasp cocoons in place). On small trees, hand-pick caterpillars or shake them off, or spray foliage with Bacillus thuringiensis kurstaki (Btk) while caterpillars are young. Use other insecticides only as labeled.

📍Where and when to find it

Look for larvae on the upper and lower surfaces of catalpa leaves; adults may be attracted to lights near catalpa trees. Pupae are in soil or leaf litter beneath host trees.

✨Fun facts

• The caterpillars are prized as live bait by anglers and commonly called 'catalpa worms' for that reason.
• While they can defoliate small trees, mature catalpa trees usually tolerate repeated feeding and regrow leaves.
• Large aggregations of caterpillars can appear suddenly because females lay clusters of eggs; outbreaks are often short-lived due to predators and parasites.

?Frequently asked questions

📷Photos of the catalpa sphinx