This past week I headed to a local park with my flashlight and bug spray at 9 p.m. and joined a group of moth “enthusiasts”. We headed out to the woods and stopped at baited trees hoping to observe some of our larger Ohio moths. We tromped around for about an hour collecting bugs and moths to view back at the shelter house with a nifty piece of equipment that magnifies the image onto a screen. My husband declined my invitation to join this adventure.
During mid-to late summer and early autumn, large unusually shaped, colorful caterpillars are often seen. According to Factsheet HYG-2015-11, Giant Caterpillars, these caterpillars, larvae of moths and butterflies, feed on leaves of various trees, shrubs, and other plants. The exact host plant or plants vary with each species of caterpillar. Most giant caterpillars are discovered when wandering across lawns, driveways, etc. These caterpillars are fully grown and they are on their way to pupation (transformation into adults) sites. They have finished eating and will cause little or no further plant damage. Therefore, controls are generally not recommended.
Moths and butterflies develop by complete metamorphosis characterized by four distinct growth stages. The egg hatches into a larva (caterpillar) which grows and molts (sheds its skin) several times before transforming into a pupal from which a winged adult emerges later.
The tobacco hornworm, also known as the Carolina Sphinx Moth larva, has seven diagonal white stripes on each side of the body and a curved red horn at the rear. The tomato hornworm, also known as the Five Spotted Hawk Moth larva, has eight curved white stripes on each side of the body and a straight black horn at the rear. Both caterpillars are green, occasionally with a brown or black tinge, and will reach a length of four inches. Food plants of both larvae include tobacco, tomato, eggplant, pepper, potato, and related weeds. The larval period ranges from 28-36 days, after which the larva burrows into the soil three to four inches deep to pupate and overwinter.
In May or June, the adult emerges. These sphinx moths are powerful fliers, and are sometimes called hawk moths or hummingbird moths because they hover while feeding on flowers.
Caterpillars can be controlled through hand-picking; however, both caterpillars are also subject to the depredations of several predators and parasitoids. Paper wasps, yellow jackets, and other wasps will grab them, chew them up, and take the remains to their nests to feed their larvae. The tiny parasitoid wasp, Cotesia congregata (Family Braconidae) inserts its eggs into the caterpillars and the resulting wasp larvae consume the hornworms from the inside out! Have you ever come upon a hornworm on your tomato plant and noticed rows of white cocoons “sprouting” on its back? A wise gardener will leave it alone, knowing that the wasp cocoons represent the potential future demise of numerous other hornworms.
We snapped beans today and shared some cucumbers with friends. The squash has slowed down a bit and the tomatoes are ripening faster. Life is good.