Hawk moths (family Sphingidae) are a widespread group of insects known for their powerful flight and robust bodies. Their larval stage consists of large, conspicuous caterpillars that are herbivores. These caterpillars consume massive amounts of plant material during development. The specific plants they eat are tied to a highly specialized diet that varies significantly among species.
Identifying the Caterpillar
Hawk moth larvae are recognizable due to their considerable size and distinctive physical features. These caterpillars possess thick, cylindrical bodies that can grow up to four inches long, making them some of the largest caterpillars found in many ecosystems. Their coloration is often green or brown, frequently featuring diagonal stripes, white granules, or prominent eyespots that help them blend into the foliage.
The most defining characteristic is the caudal spike, or “horn,” which projects from the final abdominal segment of the caterpillar. This structure, which has earned many species the common name “hornworm,” is soft, harmless, and not a stinger, contrary to common belief. The horn’s purpose is uncertain, but it may function as a decoy to divert a predator’s attack away from the vulnerable head. Identifying a species often requires noting the horn’s color, the pattern of the stripes, and the specific host plant.
Specialized Diets of Hawk Moth Species
The diet of hawk moth caterpillars is highly specialized; most species are oligophagous, feeding only on plants within a small group of related families. This selective strategy ensures the caterpillar can efficiently process the specific compounds and toxins present in their host plants. Well-known examples in North America are the tobacco hornworm (Manduca sexta) and the tomato hornworm (M. quinquemaculata), which specialize exclusively on plants in the nightshade family (Solanaceae).
These agricultural species devour the foliage of tomato, potato, tobacco, and pepper plants, often stripping a plant bare quickly. Other hawk moth species target different plant groups. For example, the grapevine sphinx (Darapsa myron) feeds on grape leaves and Virginia creeper. The privet hawk-moth (Sphinx ligustri) feeds on privet, lilac, and ash, while the elephant hawk-moth (Deilephila elpenor) targets willowherbs and fuchsias.
The Lifecycle Goal of Feeding
The volume of plant matter a hawk moth caterpillar consumes is tied to the energy demands of its life cycle. The entire larval stage is dedicated to acquiring and storing resources necessary for complete metamorphosis. Over several weeks, the caterpillar passes through growth stages called instars, increasing its body mass exponentially.
A caterpillar like the tomato hornworm can increase its size by a factor of 10,000 from the time it hatches until it is fully grown. This rapid growth requires constant, voracious feeding to build up the fat reserves that sustain the insect through the pupal stage. Once the caterpillar reaches its maximum size, it ceases feeding, its color may change, and it leaves the host plant to burrow into the soil or leaf litter to pupate. The energy stored must be sufficient to fuel the entire transformation into the adult moth.
Adult Moth Feeding Habits
The adult stage of the hawk moth contrasts sharply with the caterpillar in both appearance and dietary needs. Adult hawk moths, which are powerful, fast-flying insects, primarily sustain themselves on nectar. They are known for their ability to hover in mid-air, allowing them to precisely insert their long, coiled proboscis into the deepest parts of tubular flowers to access nectar.
This feeding behavior makes them significant pollinators, especially for night-blooming flowers. However, some hawk moth species do not feed as adults. These non-feeding species rely entirely on the energy reserves amassed as caterpillars, directing all adult energy toward reproduction.