Brown caterpillars, a common sight in various environments, exhibit a remarkable diversity in their dietary preferences. Despite similar appearances, these larval insects have highly specific feeding habits. Understanding their diet is essential for identification and appreciating their role in ecosystems.
Why Diet Matters for Brown Caterpillars
Caterpillar diets are primarily governed by host specificity. Most species are specialized feeders, relying on one or a few particular plant species for their development and survival. This specialization ensures they receive precise nutrients and chemical compounds necessary for growth and eventual metamorphosis.
Host plants also provide sustenance and chemical defenses, as some caterpillars sequester toxins to deter predators. This close relationship means a caterpillar found on a specific plant will likely feed exclusively on it. If deprived of their host plant, many caterpillars will refuse to eat and may not survive.
Common Brown Caterpillars and Their Diets
Several common brown caterpillar species are known for their distinct dietary needs.
Cutworms
Cutworms, larvae of various moth species, can be brown, gray, or black. These plump caterpillars feed on a wide range of garden vegetables, flowers, and ornamental plants, often severing stems at or just below the soil surface, particularly in young seedlings. Some species, like the variegated cutworm, climb plants to feed on leaves, buds, and fruit.
Armyworms
Armyworms, another group of brown caterpillars, are primarily pests of grasses and cereal crops like corn, wheat, oats, and rice. They move in large groups, consuming nearly all plant matter when food sources become scarce. While they prefer grasses, some species, like the fall armyworm, can feed on over 80 different plant types, including cotton, tobacco, and various fruits.
Woolly Bear Caterpillars
Woolly bear caterpillars, larvae of Isabella tiger moths, are fuzzy brown and black and commonly found in North America. These generalist feeders consume a wide variety of low-growing, broad-leafed plants. Their diet includes dandelion, goldenrod, plantain, burdock, clover, various grasses, and occasionally leafy garden plants like spinach and cabbage.
Eastern Tiger Swallowtail Caterpillars
Eastern tiger swallowtail caterpillars are brown during their first three instars, though predominantly green later. They feed on leaves of host plants from families like Magnoliaceae and Rosaceae, including tulip tree, sweet bay magnolia, and wild black cherry. They are quite polyphagous compared to many other swallowtail species.
Caring for a Found Brown Caterpillar
If you find a brown caterpillar and wish to care for it, first identify its species to determine its specific dietary requirements. Observing the plant where you found the caterpillar is the most reliable way to ascertain its host plant. Collect fresh cuttings of this plant, including both new and old leaves, and place them in a container with the caterpillar.
Ensure a suitable habitat, such as a clean jar or container with air holes. Place the plant cuttings with their stems in a small jar of water, sealing the opening with wadded paper towels or cotton balls to prevent the caterpillar from drowning. Caterpillars do not typically need a separate water source, as they obtain hydration from their food.
Regularly clean the enclosure by removing droppings, known as frass, and replacing wilted leaves with fresh ones. Avoid feeding caterpillars processed foods or random leaves, as this can be harmful or lead to starvation.