Tomato Hornworms Defoliate But Five Spotted Hawkmoths Pollinate

Summary: New World insect Manduca quinquemaculata doubles as pesky caterpillar and beneficial moth: tomato hornworms defoliate but five spotted hawkmoths pollinate.

Five spotted hawkmoths pollinate: twig73010, CC BY 2.0, via Flickr

Stages as pesky larva and beneficial moth, whereby tomato hornworms defoliate but five spotted hawkmoths pollinate, characterize the life cycle of New World insect Manduca quinquemaculata. Manduca quinquemaculata centers its life cycle on nightshades, especially tobacco (Nicotiana tabacum) and tomato (Solanum lycopersicum), as host plants.

Manduca quinquemaculata belongs to the Sphingidae family of moderate- to large-sized moths. The Sphingidae are commonly known as hawkmoths, hornworms and sphinx moths.

The common name of five spotted hawkmoth refers to the insect’s adult stage as a moth. The previous three stages (eggs, caterpillars or larvae, cocoons or pupae) have the common name of tomato hornworm. A noticeable, black-colored, hornlike structuve develops at the posterior end during the larval stage.

In the larval stage, caterpillars emerge from eggs that have been deposited singly on the foliage of host plants in the Solanaceae family, known popularly as nightshades. Cultivated tobacco (Nicotiana tabacum) and tomatoes (Solanum lycopersicum) are preferred host plants. When preferred host plants become absent or sparse in habitats, other nightshades that may be selected include bell peppers (Capsicum annuum); eggplants (Solanum melongena); potatoes (Solanum tuberosum); coyote, or wild, tobacco (Nicotiana attenuata).

Caterpillars feed on the host plant’s blossoms, foliage and green fruit. With big appetites that match their large growth spurts, tomato hornworms defoliate entire plants. Usually working downward from the top, large instars are capable of stripping plants of all leaves. The fifth, and final, instar is credited with about 90 percent of the larval stage’s foliage consumption.

At maturity, tomato hornworms burrow shallowly into the soil to form their pupal cells. The metamorphic third stage of Manduca quinquemaculata’s life cycle leads to the fourth, and final stage, of adulthood as a beneficial moth.

The five spotted hawkmoth flies at dusk. The flowers of bouncing bet (Saponaria officinalis), Japanese honeysuckle (Lonicera japonica), petunias (Petunia hybrid), phlox (Phlox spp.), pricklyburr (Datura meteloides) and tobacco (Nicotiana spp.) are preferred nectar sources.

Manduca quinquemaculata claims homelands from northwestern Mexico northward through much of the continental United States. Its distribution range is weak in the Great Plains and Gulf Coast states.

The five spotted hawkmoth also may be found in southeastern and southwestern Canada. Restricted, not widespread, distributions occur in British Columbia, Ontario, Quebec, and the Canadian Maritimes.

Habitat selection is focused on agricultural and garden sites where nightshades grow, such as agricultural crop lands, tobacco fields and vegetable gardens.

On Sunday, Sept. 4, 2016, over the Labor Day weekend, I spotted a five spotted hawkmoth in the grass near the east side of the trunk of a Virginia juniper (Juniperus virginiana) that stands near the meadow along my yard’s southern border. Although largely unresponsive, the large moth occasionally moved its first pair of legs.

The moth was located not far from the site of wild tomatoes that were abundant last summer but sparse and stunted during this summer’s extreme rainfall. Tomato hornworms have never defoliated my tomato plants. Perhaps the effective secret to their moderation or absence is the presence of marigolds. Their floral scent naturally repels tomato hornworms.

Subsequent checks revealed the moth’s secretive mobility. Facing downward, it was positioned near the base of the trunk on the juniper’s south side. Later the five spotted hawkmoth was resting in the recently mowed bramble patch along my yard’s southwestern border.

I gathered grass and green leaves from the meadow to form a soft bed in a large, plastic tray that I use for gathering flowers, foliage and nuts. I placed the quiet moth on top of some leaves and transported the tray to a wood-topped table on the southern wing of my front porch.

The five spotted hawkmoth passed away during the night. On Labor Day morning, the wings were stiff and the moth’s body seemed somewhat desiccated.

Tomato hornworms defoliate: tomato hornworm on tomato plant; defoliation has already bared a number of leaf stalks: Whitney Cranshaw/Bugwood.org, CC BY 3.0, via Forestry Images

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Five spotted hawkmoths pollinate: twig73010, CC BY 2.0, via Flickr @ https://www.flickr.com/photos/7890429@N03/4912498974/

tomato hornworm on tomato plant: Whitney Cranshaw/Bugwood.org, CC BY 3.0, via Forestry Images @ http://www.forestryimages.org/browse/detail.cfm?imgnum=5499217

For further information:

Day, Eric. “Hornworms on Tomato.”
Available @ http://pubs.ext.vt.edu/3104/3104-1551/3104-1551.html

“Five-spotted hawkmoth Manduca quinquemaculata (Haworth, 1803).” Butterflies and Moths of North America > Species.
Available @ http://www.butterfliesandmoths.org/species/Manduca-quinquemaculata

Grant, Verne, and Karen A. Grant. "Behavior of hawkmoths on flowers of Datura meteloides." Botanical Gazette, vol. 144, no. 2 (June 1983): 280-284.
Available @ https://www.jstor.org/stable/2474654?seq=1#page_scan_tab_contents
Available @ http://www.journals.uchicago.edu/doi/10.1086/337374

“How to Tell the Difference Between Tomato and Tobacco Hornworms.” Entomology Today > 2013. Dec. 14, 2013.
Available @ https://entomologytoday.org/2013/12/14/how-to-tell-the-difference-between-tomato-and-tobacco-hornworms/

“Manduca quinquemaculata (Haworth, 1803) Five-spotted Hawk Moth.” Pacific Northwest Moths > Family Sphingidae > Subfamily Sphingidae > Manduca.
Available @ http://pnwmoths.biol.wwu.edu/browse/family-sphingidae/subfamily-sphinginae/manduca/manduca-quinquemaculata/

"Manduca quinquemaculata (tomato hornworm)." CABI (Centre for Agriculture and Biosciences International) > Invasive Species Compendium > Datasheets.
Available @ http://www.cabi.org/isc/datasheet/44564

Marriner, Derdriu. “Tomato Hornworms Become Five Spotted Hawkmoths (Manduca quinquemaculata).” Earth and Space News. Saturday, Sept. 10, 2016.
Available @ https://earth-and-space-news.blogspot.com/2016/09/tomato-hornworms-become-five-spotted.html

Marriner, Derdriu. “Tomatoes Love Marigolds: Tomato Companion Planting.” Earth and Space News. Thursday, Feb. 19, 2015.
Available @ https://earth-and-space-news.blogspot.com/2015/02/tomatoes-love-marigolds-tomato.html

Moeller, Karla. “Manduca Growth Experiment.” Arizona State University Ask A Biologist.
Available @ https://askabiologist.asu.edu/manduca/introduction

“Moth Anatomy.” Wildlife Insight > Guide to British Moths.
Available @ http://www.wildlifeinsight.com/guide-to-british-moths/moth-anatomy/

NC Small Fruit and Tobacco IPM. “How to ID Two Common Hornworms.” YouTube. Dec. 11, 2013.
Available @ https://www.youtube.com/watch?v=4IRcFWakMlY

Palache, Spencer. “Farmers Menace to Colorful Hoverer: The Five Spotted Hawk Moth.” Havasi Wilderness Foundation. March 16, 2015.
Available @ http://www.havasiwf.org/farmers-menace-to-colorful-hoverer-the-five-spotted-hawk-moth/

Villanueva, J. Raul. “Common name: tobacco hornworm scientific name: Manduca sexta (Linnaeus) (Insecta: Lepidoptera: Sphingidae), common name: tomato hornworm scientific name: Manduca quinquemaculata (Haworth) (Insecta: Lepidoptera: Sphingidae).” University of Florida Entomology and Nematology Department > Featured Creatures. June 1998. Latest revision November 2013.
Available @ http://entnemdept.ufl.edu/creatures/field/hornworm.htm