This week we are talking cats – caterpillars that is. There are three that should be on your radar this time of the year. They are the good, the bad and the ugly.
The Good: The Monarch (Danaus plexippus)
Can you imagine only eating one kind of food over your entire lifetime? If you were a monarch caterpillar, your diet would only consist of milkweeds (Asclepias spp.).
Monarch eggs are laid individually on milkweed leaves. The caterpillars, or larva, begin their life by eating the eggshell after hatching, and then ingesting the leaf tissue of milkweeds. As the caterpillar consumes more and more milkweed leaves, it “grows” through five stages or instars. At each stage, it molts or sheds its skin. Once caterpillar feeding is complete, the insect pupates, transforming from a caterpillar to a beautiful orange, black and white butterfly.
To attract monarchs to your landscape, you must have milkweeds for the caterpillars, and a variety of flowering plants that the butterflies seek out for the nectar. They are not as picky as caterpillars and will visit a variety of flowers. Since there are multiple generations, and you will see adults throughout the summer and into the early fall, providing a seasonal smorgasbord of flowers is important.
The Bad: The Gypsy Moth (Lymantria dispar)
The diet of this caterpillar is unbelievably diverse, feeding on hundreds of different types of trees and shrubs. Favorites include oaks, crabapples, witchhazels and spruces. The caterpillars hatch in the spring from an egg mass that can contain between 50 to 1,500 eggs. These tan, quarter-sized masses can be laid on any surface. Once hatched, the larvae begin a trek to find a suitable host. Small caterpillars eat a small amount of leaf tissue, and as caterpillars get larger, so does their appetite. Large mature trees can be totally defoliated in a single season. Deciduous trees can recover, but it is often lethal on evergreens.
Currently, gypsy moth caterpillars are small, but will soon become more evident as leaves begin to “disappear” and frass, or insect poop, falls.
In July, caterpillars will begin to pupate, and ultimately emerge as either a flightless white female moth or a brown male moth with feather-like antenna who flies during the day in a zigzag pattern in search of his mate. Adult moths do not feed, so control at this stage is not recommended.
The Ugly: Bagworms (Thyridopteryx ephemeraeformis)
How ugly are bagworms? They are so ugly that the caterpillars spend nearly their entire life inside a handmade bag, poking their heads out for their plant-based meals. The insects pupate inside their individual bags. The adult male emerges from his bag to seek out a female mate who actually never leaves her bag. They mate, and she fills her bag up with eggs and dies.
Because bagworms spend so much of their lives inside a bag, control can be challenging. Hand removal and disposing of bags is recommended when populations are low. Insecticides can be very effective after caterpillars hatch, but before they build their bags and are protected inside.
For more information about each of these “cats” you could see in your landscape now, check out the recommended links or contact your local Extension office. Unsure of what caterpillar you are seeing, send me a photo to stone.91@osu.edu and I can help determine if it is good, bad or ugly.
First Published June 10, 2019, 8:00 p.m.
