The Ugly Hornworm Larvae and the Amazing Moths They Become
Tomato Hornworm Caterpillar in Arizona
The Hornworm Deserves a Little Respect
The Tomato Hornworm (M. quinquemaculata) has a very difficult life. What if you had a stealth-like drone, hot off the assembly line, full of poison or bio-chemical material, come right at you, attack you and leave your stomach full of parasites to eat you alive? Do you think you might deserve a little compassion? Well, these ugly Hornworms have obtained my empathy, if not perhaps quite yet my compassion. I'm no gardener and the closest I plan on ever getting to one of these huge, green Arizona caterpillars is the jar I photographed for this hub. But these larvae really do have a tough time trying to survive. Each of them lives in absolute danger their whole short life and many die a horrible early death.
The only protection the Hornworm has is its truly amazing camouflage of body color and design. Its green body looks exactly like the tomato plant's leaves and branches.1
There is also a Tobacco Hornworm (Manduca Sexta) which crawls all over the same plants the Tomato Hornworm prefers. The Tobacco Hornworm's camouflage is just as good and very similar.
See How Well Camouflaged this Caterpillar Is
The Tomato Hornworm and the Tobacco Hornworm
The tomato hornworm or Manduca gunquemaculata is actually, of course, a caterpillar. It thrives on tomato plants and derives its name from the pointed black horn-like structure of the end of its tail. The tomato hornworm larva is green and can grow to a length of four inches. While in the larva stage, the tomato hornworm has seven V-shaped markings on the sides of its body. If the hornworm manages to survive, it becomes a Five-Spotted Hawkmoth with a wingspan up to five inches across.
The tobacco hornworm also likes to feed on tomato plants. It differs from the tomato hornworm in the fact that the 'horn' on the end of its tail is red. Another difference is that the tobacco hornworm's body has seven diagonal lines rather than V-shaped markings. The tomato hornworm and the tobacco hornworm can be found feeding together on tomato plants and pepper plants. Guess where these guys like to spend their daytime hours? They rest and hide in the interior of the plants where an unsuspecting gardener might not even notice them as they blend in so well with the foliage.2
Reacting to a Big Green Hornworm in your Garden
What would you do if you found one of these Hornworms on a tomato plant in your garden?
Scientific Classification of the Tomato Hornworm Caterpillar
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Insecta
- Order: Lepidoptera
- Family: Sphingidae
- Genus: Manduca
- Species: M. quinquemaculata
From Stage to Stage Until a Moth Emerges
The hornworm larva goes through four larval stages within about a month until it reaches its full size. Each larval stage is interrupted by a molt of the 'integument' and the stage between each molt is called, in the bug world, an instar.3
When it becomes full size, the caterpillar buries itself in the soil to pupate. In two weeks, a moth emerges from the soil.
Main enemies of Hornworms
Hawk Moth of Southeastern Arizona
It's a Very Dangerous World for the Hornworms
There are several insects that parasitize hornworms. One is the braconid wasp. It lays its eggs on the caterpillar. The larvae hatch and begin to eat the inside of the caterpillar until the wasp is ready to pupate. As a gardener, if you're reading this, you might already have seen this happen where white projections begin to stick out of a hornworm's body. One site where I was reading up on this, stated the gardener is best at this point to leave the hornworm there in its afflicted state because the wasp will kill the hornworm soon enough and also look for other hornworms to kill.5
This seems very cruel to me and perhaps to you. A great many people, however, consider these two types of hornworm larvae to be very economically destructive to crops in North America. The larvae -- apparently -- 'attack' potato, tomato and tobacco crops. In reality, they are just trying to survive. But really, they can strip plants bare. The agricultural scientists have a few ways farmers can control this larvae species. One method is with the use of a natural enemy to the hornworm: the braconid wasp (Apanteles congregatus) which parasitizes the larvae as explained above. Another method is by pesticide such as Bt (Bacillius thuringiensis) dust.6
Apparently, you can get this 'Bt' product at most big stores like Lowe's. You don't have to be a farmer with hundreds of acres to be able to purchase it. I don't know if it is a natural product or quite the opposite and not something you want in your tomatoes.
Braconid Wasp Larvae Torturing This Hornworm
A Giant Hawk Moth with His or Her Long Proboscis
What Kind of Moth Does the Tobacco Hornworm Become?
The tobacco hornworm becomes a hawk moth, usually gray in color -- not so pretty as the tomato hornworm's final stage. The hawk moth is also known as the sphinx moth or Hummingbird Moth. The reason it is dubbed the Hummingbird Moth is because it has the ability to hover with its stout body, narrow forewings and short hindwings. The wingspan can be between 2 inches and 8 inches across. The most amazing feat of these Hawk Moths is they pollinate flowers much like the bees do. Both the developed and pupated larvae of the Tomato Hornworm and the Tobacco Hornworm pollinate flowers! Some of these Hawk Moths have very long proboscis (feeding organ) to obtain the nectar from the flowers.6
Male Hawk Moth, Formerly a Tobacco Hornworm Larva
Female Outcome of the Tobacco Hornworm—the Hawk Moth
Fly like a Hummingbird, Drink Nectar and Pollinate
The adult hornworms which become big moths with the various names of Hawk Moth, Sphinx Moth or -- the nickname -- Hummingbird Moth are strong flyers due to the build of their bodies. They have a superficial resemblance to a hummingbird, and they have the real abilities of the bees to pollinate although it's rather accidental on their part, but their main goal is to feed on the nectar of certain flowers. These moths are nocturnal although once in a while you might see one fluttering from flower to flower in the day time.7
Moth Hovering and Feeding on a Flower's Nectar
Short Video of Hummingbird Moth—Sphinx, Arizona, Normal & Slow Motion
Just a Repeat, in Case You Missed It
The adult stage of the tomato hornworm and the tobacco hornworm are Hawk Moths also known as Sphinx Moths. These same moths are sometimes called Hummingbird Moths because with their two-to-eight inch wingspans and plumpish body -- and their strong flying abilities, especially their skill in hovering -- they are often mistaken for hummingbirds. They are amazing little creatures.
Hawk Moths like to Feed on Four O'Clock Flowers
The Datura Flower -- One of the Hawk Moth's Favorites
- Hornworms in the Low Desert. Last updated October 19, 2005. http://cals.arizona.edu/maricopa/garden/html/t-tips/bugs/hornworm.htm
- Backyard Gardener. Sphinx Moths - October 18, 2006 Jeff Schalau, County Director, Associate Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County. https://ag.arizona.edu/yavapai/anr/hort/byg/archive/sphinxmoths.html
- Manduca quinquemaculata http://en.wikipedia.org/wiki/Manduca_quinquemaculata
- Maricopa County Cooperative Extension Home Horticulture: Hornworm/Sphinx Moth
- Encyclopedia Britannica. http://www.britannica.com/EBchecked/topic/257473/hawk-moth
© 2014 Pamela Kinnaird W