Happy Friday, Moth Fans!!! We hope you’re having a great Friday. How many of you plant vegetable gardens in your yards? Today’s featured species is common to gardens, but you usually don’t see the adults! Usually you’ll find the caterpillars eating the leaves of your tomato plants. Today we’re introducing you to Manduca sexta---the Tomato Sphinx. In America we say Sphinx, because the Latin family name is Sphingidae (the “G” is soft). In the rest of the world they say Hawkmoth. You’ll often hear the caterpillars called Tomato Hornworms, or just Tomato Worms. But whatever you call it, it’s one of America’s most interesting moths.
The family Sphingidae is a reasonably large family with about 1500 species worldwide. In most of North America the largest size Sphinx moths belong to the genus Manduca. The Tomato Sphinx usually has a wingspan in the 3 to 4 inch range. Sphinx moths have a large body to wing-area ratio, making them look more like streamlined airplanes. And they are very aerodynamic fast flyers. They can even hover! The adult moths have very long tongues that they coil up under their heads when not in use. When feeding, they will usually hover in front of a flower, uncoil their long tongues, and move from flower to flower like hummingbirds. Most of the moths in the genus Manduca are relatively drab and cryptic in color, usually in shades of grey or brown with white, cream, or black markings. They can easily be confused with each other. But the most common characteristic of the genus is the prominent bright yellow spots on the abdomen. And Manduca sexta has very bold spots, as you can see in our photo today. The males and females share the same cryptic pattern. When the wings are closed, they are folded back covering the yellow spots, giving the moth a dark arrowhead shape. They are perfectly camouflaged to hide on a tree branch or on the bark of the trunk.
But it’s really the caterpillars that are more interesting. The caterpillars are various shades of green with diagonal white lines. Below the lines are a series of black spots on each segment of the body. These black spots are just part of a relatively simple pattern. But in the center of each spot is a tiny hole called a Spiracle that allows the caterpillar to breathe. All Insects use Spiracles to breathe, but often they are hidden in a more complex pattern or are covered with scales or hairs. On the rear of the caterpillar is a “spike” that looks like a stinger, but it’s harmless. It just looks dangerous. When the caterpillars are frightened, they rear up their heads and jerk their bodies side-to-side, trying to scare off their predators. This combined with the spike on the tail works pretty well most of the time. Unfortunately for the caterpillar, there is one predator that will not be deterred---a tiny parasitic wasp that has evolved to prey exclusively on Manduca sexta and closely related species. This wasp which is less than 5 mm. in length, finds the caterpillars when they are young, and lays its eggs just beneath the caterpillar’s skin, eventually killing the caterpillar. As the caterpillar grows, the wasp larvae grow inside, feeding on the caterpillar’s growing body!!! And just when the Tomato Sphinx caterpillar is ready to pupate, the parasitic wasp larvae emerge from the caterpillar skin and make cocoons on the caterpillar itself. Sometimes there are a few, and sometimes there are many, like in our photo today. The wasps then emerge, and look for another caterpillar to lay their eggs in. Nature can be pretty cruel, if you’re a Tomato Sphinx!
For the lucky caterpillars that manage to evade the wasps and complete their caterpillar stage, it’s time to shed their skin a final time and become a dormant Pupa. The Tomato Sphinx pupa is very interesting. Although it has a normal pupal shape, there is a special “free-standing” tongue compartment that looks like a pitcher handle. The Tomato Sphinx tongue is too long to fit inside the pupa, so it has evolved this external tongue case to protect it from getting damaged while developing in the hibernating pupa. Most pupae are formed under a few inches of soil in a tunnel that the caterpillar digs as its last caterpillar task. Then the pupa overwinters in relative safety underground until it hatches into a moth the following spring. It’s really an amazing life cycle, and because it is so interesting, many amateur collectors like to raise them so they can observe them first hand.
Right now in Northern Illinois, we’re approaching the best time to find Tomato Sphinx caterpillars. The Tomato plants are bearing tomatoes, and while you’re picking them from your garden, you just might find one of these very interesting caterpillars. They are normally very well camouflaged, so even though they are 2 to 3 inches long now, you might overlook them. And just in case you don’t want to raise them and wait until next spring to see them, you can see them right now in our Wonders Of Nature department. They are a traditional favorite with young collectors. And because they are a local species the prices are very reasonable, usually starting at less than $50.00 framed!!! They’d make a great gift for the young Entomologist in your family. See you on the trail!
And don’t forget to visit the Friday Flyers archive on our website. You can now refer to all of the past editions complete with all the photos, in a stable and permanent format. We hope you’ll visit our website and check it out at:
We hope you enjoyed this week’s edition of Friday Flyers. We love sharing our interest in butterflies and insects with you. Please enjoy the photos we have posted with this week’s edition, and be sure to see all the previous pictures in our Friday Flyers album. Remember to “like” our Wonders Of Nature page, and be sure to pass it along to all your Facebook Friends. We hope you’ll visit our Wonders Of Nature department soon, and we look forward to seeing you.