From mid-August until September’s first frost, insects overwhelm our senses outdoors.
Consider the constant white noise of crickets; the droning, shrill stridulating of katydids; the evening luminescence of fireflies; the wasps and ants that set their nests under the eaves or in the garage; the grasshoppers dining in your yard and garden; or the eye-catching Monarch butterflies visiting your gardens and wildflowers. Many late summer high populations of insects feed the seasonally expanded populations of young birds, mammals, fish, and predatory invertebrates. During these weeks, the three insects that have caught my attention in different places are caterpillars with some truly creepy qualities: poison defense; gluttonous appetites; and humongous size.
In the Woods: One sunny morning recently, I was out walking with Jessie the dog, and we passed under a large but failing butternut tree. A glint in the air caught my attention and, looking up, I saw over a hundred small, white, hairy caterpillars dangling, each on its own silk thread, from the tree’s few leafy branches. Ultimately, they dropped down to the ground. Investigating, I found these to be the larvae of Hickory Tussock Moths (Lophocampa caryae), a familiar species in the forests from Minnesota to eastern North America, where they feed on hickory, walnut, pecan, willow, elm, and oak foliage. This species is in a subfamily known as the tiger moths because of their adult yellow/brown color; they are handsome moths usually seen in late spring emerging from their wintering pupae.
The Hickory Tussock Moth caterpillars, vulnerable to predators, have evolved protective toxic chemicals, so don’t eat them! But more important, their tiny hairs also carry toxic chemicals, and if they touch your skin, the contact may cause a painful rash. This is true of many other species of hairy caterpillars, so curious children (and impetuous adults) should be discouraged from handling any of them.
In the Orchard: On warm, sunny days of late summer, we find unsightly clumps of a silk-like web on the branch tips of our apple trees, as well as on wild black cherry trees. Taking a close look, you would see a colony of small, squirmy caterpillars within the silky shelter, where they will feed on foliage. These are known as Fall Webworms (Hyphantria cunea) and are often mistakenly referred to as Tent Caterpillars, different critters that operate deep in the crown of deciduous trees in the spring.
The cluster of these Webworm caterpillars builds their sloppy web in a location that provides both sunshine and abundant foliage for food. The web is a busy, social home where mate identification takes place, and where the group defends against predators by forming a wiggling mass within the tangling web. But later the Fall Webworms depart to creep slowly down the tree’s trunk for overwintering and transforming into inactive, sheltered pupae in the leaf litter. The next-generation adult moths will emerge at the same site, lay their eggs on the tree’s fresh new foliage, and new larvae caterpillars will soon go to work.
The damage these Fall Webworms may cause on orchards can be unsightly and troublesome. But in August I snipped several infested branches off my apple trees, offered them to our young chickens, and the delicacy was frantically welcomed! Even when I’m pruning, though, I know the Webworms will be back.
In the Garden: Among vegetable gardeners, the most popular home-grown foods are probably tomatoes. They are also very popular to Manduca quinquemaculata, more familiarly known as the Tomato Hornworm. This beast is startlingly large (4 inches long); it feeds on the leaves, stems, and fruit of the tomato plant successfully because of its discretion and its color camouflage. The Tomato Hornworm moth lays her eggs on the underside of tomato leaves; when the larvae emerge a week later, they grow in half-a-dozen stages as eating machines. That 3-week growth is almost impossible to observe and so rapid that the large caterpillar is easy to overlook. These Hornworms reach their full size and their greatest damage by late August. Later the pupa settles into the soil until the following spring when the adult moth emerges.
The Tomato Hornworm gets its name from a horn-like spiky protrusion on its last body segment. Like “eye spots” on many moth wings, the “horn” repels potential predators. The moth is a very large “sphinx moth” looking like a hummingbird that may visit your garden blooms.
Tomato plants are very closely related to peppers, potatoes, and tobacco. With parallel adaptive evolution, the Tobacco Hornworm is closely related to the Tomato Hornworm: two very large green, startling creatures with bright marks on their flanks, fake rear weapons, and damaging appetites. The caterpillars of these two species can be removed from the garden by hand, foot, or a flock of curious chickens.