Manduca quinquemaculata, the five-spotted hawkmoth, is a brown and gray hawk moth of the family Sphingidae. The caterpillar, often referred to as the tomato hornworm, can be a major pest in gardens; they get their name from a dark projection on their posterior end. Tomato hornworms are closely related to (and sometimes confused with) the tobacco hornworm (Manduca sexta). This confusion arises because caterpillars of both species feed on the foliage of various plants from the family Solanaceae, so either species can be found on tobacco or tomato leaves. Thus, the plant on which the caterpillar is found does not indicate its species.
Video Manduca quinquemaculata
Morphology
Egg
Eggs are large and range in color from pale green to off-white.
Larva
M. quinquemaculata larvae are large green caterpillars reaching a length of up to four inches when fully grown. The caterpillars have a dark pointed projection on their rear end that earns them the name "hornworm." Although the tomato hornworm, M. quinquemaculata, can be confused with the tobacco hornworm, M. sexta, the larvae of these species can be distinguished by their lateral markings: Tomato hornworms have eight V-shaped white markings with no borders and dark blue or black horns; Tobacco hornworms have seven white diagonal lines with a black border and red horns.
Adult
Adults are large, with a wingspan of up to five inches. The wings of the moth are brown and gray with large mottled front wings and smaller hindwings with light and dark zig-zag patterned bands. The abdomens are brown and white with a row of five yellow spots down each side. The moths of M. quinquemaculata and M. sexta can be distinguished by the number of spots on their abdomens, with M. quinquemaculata having, as its name suggests, five.
Maps Manduca quinquemaculata
Range
M. quinquemaculata is found throughout the United States, northwestern Mexico, and even southern Canada, but is less frequently found throughout the Great Plains and the southeast.
Food plants
Larva
Tomato hornworms are known to eat various plants from the family Solanaceae, commonly feeding on tomato, eggplant, pepper, tobacco, moonflowers and potato. Accordingly, they are often found on defoliated tomato plants, the caterpillar clinging to the underside of a branch near the trunk. They are difficult to spot due to their green color. Tomato hornworms fluoresce differently from tomato leaves. Using an ultraviolet light source of 375 nm and viewed behind a blue-blocking filter (yellow or amber filter), a tomato hornworm fluoresces in bright green while a tomato leaf appears deep red/amber. This sharp color contrast helps gardeners locate tomato hornworms at night. They can be reduced by planting marigold flowers around these plants.
Adult
Adult diet
Adults feed on nectar from flowering plants including Datura meteloides, Oenothera caespitosa, and mirabilis multiflora. Most of the food plants they target, including the three listed here, have large, fragrant, white flowers.
Interactions with host plants
Hawkmoths, including M. quinquemaculata, are the primary pollinators of D. meteloides. The length of the moth's proboscis (around 10 cm) is well suited for retrieving nectar from the flowers. Aside from being a host plant for M. quinquemaculata, D. meteloides has also been used by humans for its opioid effects. D. meteloides contains tropane alkaloids, which are present throughout the plant including in the flowers. These alkaloids have an intoxicating effect on the moth, which display erratic flight patterns as well as uncoordinated, and often unsuccessful, landing attempts after consuming the nectar. Despite the impairment the nectar causes, the moths have been observed returning to the flowers for more. It has been hypothesized that the "spiked" nectar offered the moths reward beyond just nutrients.
Both Datura meteloides and Oenothera caespitosa are also dependent on hawkmoths for pollination. M. quinquemaculata has been found to feed from Oenothera caespitosa first and only later to visit Datura meteloides, indicating a preference for the former.
Life cycle
Oviposition
Females lay eggs singly on the surface of host plant leaves in late spring. Larvae hatch after approximately one week. The female decides where to lay eggs based on an assessment of the risk of predation her offspring will face. On the tobacco plant Nicotiana attenuata, young leaves close to a plant's stem are more protected from predators and larvae that grow there gain more mass than larvae elsewhere on the plant, so females prefer to oviposit on these leaves.
Larva
Caterpillars hatch in late spring to early summer. They develop through five instars to reach maturity. In warmer climates, two generations of caterpillars can coexist in a single summer. Once fully grown, caterpillars fall from their host plants to pupate.
Pupa
Caterpillars pupate in early fall. After pupation, M. quineuqmaculata overwinter in the soil near their host plants, with adults emerging the following summer.
Adults
Shortly after adults emerge from the soil, they mate and females lay their eggs on host plants, renewing the life cycle.
Relationship with M. sexta
M. quinquemaculata and M. sexta are both large hawkmoths of the genus Manduca. The two species have similar appearances as both larvae and adults and share common food sources, including tobacco. Past research, knowing that the two species are similar, has referred to them as sister species. However, a recent phylogenetic analysis from Kawahara et al. (2013) has found that the two species, though closely related, are not sister species. The authors tracked the ancestral origin of both species to Central America, where the two species diverged from one another.
Threats
Because the larvae are pests of crop plants such as tomatoes and tobacco, they face threats from both natural predators and from human intervention.
Wasps
The parasitoid wasp Trichogramma attacks M. quinquemaculata eggs. The larvae of the wasp develop in the egg, preventing the development of the caterpillar larvae. Trichogramma is a natural enemy of the M. quinquemaculata and has also been used as a biological control agent by humans.
A second parasitoid moth, Cotesia congregatus of the family Braconidae, also kills M. quinquemaculata. Adult females lay their eggs inside the skin of the hornworm caterpillar. After hatching, the wasp larvae use the organs and tissues of the caterpillar as food sources before burrowing out of the skin and pupating on the back and sides of the caterpillar. Once the wasps have emerged from their cocoons, the weakened caterpillar dies. Like the parasitoid wasp mentioned above, these wasps have also been suggested as a means of biological control of the tomato hornworm.
Traps
Adult M. quinquemaculata are most active in flight after dark. Early studies found that the moths are attracted to blacklight, which is used as a lure in some traps. Although the traps can be used for research and the moths can be released after capture, traps like these have been suggested as a means of population control, though one study found that the reduction in population was not strong enough to significantly impact population size.
Images
References
External links
- The Tomato Hornworms Colorado State University Cooperative Extension, Denver County
- Manduca quinquemaculata, Butterflies and Moths of North America
- Tomato hornworm on the UF / IFAS Featured Creatures website
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