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= Manduca quinquemaculata    =

Manduca quinquemaculata, known in the larval stage as the tomato hornworm and in the adult stage as the five-spotted hawkmoth, is a species of moth common in North America. In the larval stage, the species is known as a pest of several crop plants, including tobacco and tomato (its namesake). The adult, which depends on nectar as its primary food source, is an important pollinator of several flowering plants.

Geographic range
M. quinquemaculata can be found across North America from northern Mexico in the south to southern Canada in the north. Although they are found throughout the United States, population density is highest in the western half of the country. Like other hawkmoths, adults are migratory and have been found to fly long distances within their range.

Habitat
Distribution of individuals is dependent on host plants. Accordingly, caterpillars can be found in and around vegetable gardens and tobacco fields. Because they are migratory an depend on nectar as a food source, adults can be found in a wider variety of habitats, including mountains and tobacco fields.

Caterpillars
Known as a garden pest, M. quinquemaculata larvae feed on the leaves and fruit several crop plants in the nightshade family, including tomatoes, potatoes, eggplants, and tobacco. The caterpillars grow and eat quickly, especially in later instars.

Adult diet
Adults feed on nectar from flowering plants including Datura meteloides, Oenothera caespitosa, and mirabilis multiflora.

Interactions with host plants
A 1983 paper described the relationship between M. quinquemaculata  and the flowering plant Datura meteloides. 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. The authors of the study found that these alkaloids have an intoxicating effect on the moth, which displayed erratic flight patterns as well as uncoordinated, and often unsuccessful, landing attempts after consuming the nectar. Despite the impairment the nectar causes, they have been observed returning to the flowers for more. The authors 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.

Oviposition
Females lay eggs singly on the surface of host plant leaves in late spring. Larvae hatch after approximately one week.

A 2002 study from Kessler and Baldwin tracked the preferences of ovipositing females on the tobacco plant Nicotiana attenuata. The authors found that females prefer to lay eggs on young leaves close to the plant’s stem. The larvae on young leaves faced decreased predation and gained more mass than larvae elsewhere on the plant. The authors suggest that risk of predation drives females’ preferences in oviposition.

Larval stage
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.

Pupal stage
Caterpillars pupate in early fall. After pupation, M. quineuqmaculata overwinter in the soil near their host plants, with adults emerging the following summer.

Adult stage
Shortly after adults come out of the soil, they mate and females lay their eggs on host plants, renewing the life cycle.

Eggs
Eggs are large and off-white.

Caterpillars
M. quinquemaculata larvae are large, reaching a length of up to 4 inches when fully grown. They are green with a series of horizontal v-shaped markings along their sides. Within each of these markings is a black spot. The caterpillars have green-black spiked protrusion from their heads that has earned them the name “hornworm.” M. quinquemaculata, the tomato hornworm, can be mistaken M. sexta, the tobacco hornworm, but there are multiple distinguishing features. The tobacco hornworm’s spike is red rather than green-black, and it lacks the white v-shaped markings found on the tomato hornworm. Instead, the tobacco hornworm has a series of diagonal white lines down its sides.

Adults
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.

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 also tracked the ancestral origin of both species to Central America, where the authors find that 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 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 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.