Introduction
Manduca is a genus of moths in the Family Sphingidae, the sphinx moths and hawk moths. Many caterpillars in this family are commonly known as “hornworms,” because they have a horn at the end of their abdomen. There are 8 species of Manduca in the United States, and two others that are rare strays. This guide will focus on the 8 species that are more commonly found. This guide will help you identify the moths and caterpillars that can be found in the USA.
Manduca sexta
Manduca sexta has six orange spots on each side of its abdomen. It has a wingspan of 3.75 to 4.75 inches. It lives throughout most of the USA. In Louisiana and Florida there are several broods per year but in the rest of its range it flies from May to October. The caterpillar is green with seven diagonal white lines down its body. The caterpillar has a red or yellow horn on the end of its abdomen (the horn is yellower when it's young and red when it's an adult). You commonly find them on tomato plants but they can be found on many plants in the Solanaceae family as well as some other plants. It is also known as the tobacco hornworm, the six spotted hawk moth or the Carolina sphinx.
Manduca sexta adult. Photo by Levi smith @origamilevi
A not fully matured Manduca sexta caterpillar parasitized by Cotesia congregata. photo by sarah smith @sarahbartos22
Manduca quinquemaculatus
Manduca quinquemaculatus has five orange spots on each side of its abdomen. It is similar to M. sexta but is slightly larger with a wingspan of up to 5.1 inches. It lives throughout most of the USA. There are multiple broods per year in Florida and Louisiana and one to two broods throughout the rest of its range. Its caterpillar is commonly mistaken for M. sexta. The caterpillar is green or black with eight v-shaped markings over each spherical and a blackish horn on the rear of the caterpillar. These caterpillars can be found on many plants in the Solanaceae family. They are also known as tomato hornworm or five spotted sphinx.
manduca quinquemaculatus adult. photo by J. Bailey @silversea_starsong
manduca quinquemaculatus caterpillar. photo by J. Bailey @silversea_starsong
Manduca rustica
Manduca rustica has three sets of yellow spots on its abdomen. It lives in New England, southern USA, southwestern USA and California. It is easily recognized by the white markings on its wings. It has a wingspan of 3.10 to 5 inches. The only similar moth ever recorded in the USA is M. albiplaga which is larger. There are several broods from May to October in Louisiana and two broods from July to November in the rest of the range. The caterpillars are green with seven diagonal white lines with a blueish border down each side of the body and a rough yellow horn on the rear of the caterpillar. The caterpillar feeds on many types of plants including fringe tree, ash and jasmine. It is also known as the rustic sphinx.
manduca rustica adult. photo by J. Bailey @silversea_starsong
manduca rustica caterpillar. photo by Tom Kennedy @tomkennedy
Manduca brontes
Manduca brontes can be found in Florida. The caterpillar is green with yellow and blue diagonal lines down the sides of its body and a yellowish horn on the end of the caterpillar. The caterpillar feeds on Tecoma stans (Yellow Elder), Fraxinus americana (White Ash), Fraxinus excelsior (European Ash) and Fraxinus platycarpa. It is also known as the brontes sphinx or the Cuban sphinx.
Manduca muscosa
Manduca mucosa's range is in New Mexico and Arizona. Its wingspan is 4 to 5 inches. It is active for one flight from mid-July to early August in southern Arizona. The caterpillar is green, yellowish green or whitish green with seven yellow lines down each side of its body and a green horn on the end of the caterpillar. It also has two large bumps near its head. The caterpillar might feed on plants from Solanaceae, Verbenaceae, and Bignoniaceae. It is also called the muscosa sphinx.
Manduca muscosa adult. Photo by @jimeckert49
Manduca muscosa caterpillar. Photo by Ricardo Arredondo T. @elrayman210
Manduca florestan
Manduca florestan lives in New Mexico and Arizona. Its wingspan is 3.75 to 4.125 inches. There is one brood a year from late June to early August. The caterpillar is a pale blue or green with a horn on the end of its abdomen. the caterpillar feeds on trumpet bush and fiddlewood. It is also known as the florestan sphinx.
manduca florestan adult. photo by J. Bailey @silversea_starsong
Manduca jasminearum
Manduca jasminearum’s range is from Connecticut south to northern Florida and west to Missouri and Mississippi. Its wingspan is 3.30 to 4.125 inches. There are two broods from May to September. The caterpillar feeds on ashes, lilacs and elms. It is also known as the ash sphinx.
manduca jasminearum adult. photo by César Andrés Castillo @cesarcastillo
Manduca occulta
Manduca occulta is similar to M. sexta. The differences are M. occulta is smaller and has browner forewings. Its range is in southern Arizona and in southern Florida (rarely). In Florida it has been recorded flying in September. Its wingspan is 4.10 to 4.75 inches. The caterpillar is green with light blue around the spiracles. It feeds on plants in the solanum and cestrum genera. It is also known as the occult sphinx.
manduca jasminearum adult. photo by Marco Zozaya @marcozozaya
Distinguishing adult M. occulta from M. sexta
M. occulta and M. sexta can look very similar as adults. There are two features that can help you distinguish between these species. First, on M. occulta, the forewings are usually browner, while on M. sexta, they are more grey. Second, the forewing fringe (bottom border of the forewings) on M. occulta has equal portions of grey and white checkering, while on M. sexta, the forewing fringe has smaller portions of white and larger portions of grey in its checkering.
Conclusion
I think that sphinx moths are underappreciated, because people think that all sphinx moth caterpillars are garden pests. In fact, there are hundreds of species of sphinx moths that cause no harm to garden crops and even benefit plants through pollination. There is also misidentification of sphinx moths, and where I live in Vermont, what most people call the “tomato hornworm” is actually M. sexta, the tobacco hornworm, and there are other sphinx moths not in genus Manduca that are mistaken for pests and killed because of it. A local farm in my area posted a picture of a "tomato hornworm" moth that they killed, and warned people on social media to look out for these moths in their gardens. The moth they posted was actually the Pink-spotted Hawkmoth (Agrius cingulata), which is very rare (almost non-existent) in Vermont. I hope you take the time to identify these moths and think twice before accusing them of being pests. If you have any suggestions, contact me.
similar sources
SPHINGIDAE OF THE UNITED STATES
butterflies and moths of north America