Tomato hornworms, often seen as garden pests, undergo a complete transformation to become large moths. These moths are specifically the Five-spotted Hawkmoth (Manduca quinquemaculata). This article aims to clarify the common association of this moth with the term “hummingbird moth.”
From Caterpillar to Hawkmoth
Tomato hornworms undergo complete metamorphosis to become hawkmoths. The larval stage is a large, green caterpillar with distinctive white V-shaped markings and a black horn-like projection on its rear. These caterpillars are voracious eaters, primarily feeding on Solanaceae plants like tomatoes, potatoes, eggplants, and tobacco. They grow significantly, reaching lengths of up to 4 to 5 inches.
Once fully grown, the hornworm burrows several inches deep into the soil to pupate. During pupation, the caterpillar transforms into a dark brown, elongated oval pupa. The pupa features a “jug handle” projection, which protects the developing moth’s long proboscis. This stage can last from a few weeks to several months, with pupae often overwintering in the soil.
The adult Five-spotted Hawkmoth (Manduca quinquemaculata) emerges from the pupa. This is a large, robust moth with a wingspan exceeding five inches. Its wings are mottled grey-brown, and its abdomen has five pairs of distinct orange or yellow spots, giving it its common name.
Clarifying “Hummingbird Moth” Identity
The term “hummingbird moth” can be applied to several different moth species. The Five-spotted Hawkmoth (Manduca quinquemaculata), which develops from the tomato hornworm, is one such moth often colloquially referred to as a “hummingbird moth.” This is due to its large size, rapid wing beats, and its behavior of hovering while feeding on nectar, which closely resembles a hummingbird in flight.
However, there are also moths from a different genus, Hemaris, which are known as “clearwing hummingbird moths.” These include species like the Snowberry Clearwing (Hemaris diffinis) and the Hummingbird Clearwing (Hemaris thysbe). Hemaris moths are typically smaller than Manduca species and have fuzzier bodies. A distinguishing characteristic of many Hemaris species is that they lose scales from parts of their wings shortly after emerging, creating transparent, “clearwing” sections.
Despite their similar hovering and nectar-feeding behaviors, tomato hornworms specifically transform into the Five-spotted Hawkmoth (Manduca quinquemaculata). They do not turn into the Hemaris clearwing moths, which belong to a different lineage within the same moth family, Sphingidae. Both groups showcase remarkable adaptations for aerial feeding, but their larval forms and adult appearances differ.
The Hawkmoth’s Place in Ecosystems
The adult Five-spotted Hawkmoth plays a significant role in its ecosystem, primarily as a nocturnal pollinator. These moths are equipped with a long proboscis, often around four inches in length, which they unroll to reach nectar deep within flowers. This adaptation makes them effective pollinators for night-blooming flowers with long, tubular corollas, such as moonflowers, petunias, honeysuckle, and evening primrose.
Adult hawkmoths feed exclusively on nectar, sustaining their energetic, fast flight. Their powerful wing muscles allow them to fly at speeds up to 12 mph and to hover precisely in front of blossoms while feeding. This hovering flight and their large size contribute to their resemblance to hummingbirds. Although their caterpillar stage can be considered a garden pest, the adult hawkmoths are beneficial nocturnal pollinators, contributing to the reproduction of many plant species.