There are at least 28 species of sphinx moths (family Sphingidae) in California. Also called hawk moths or hummingbird moths, sphinx moths are named for the behavior of larvae when threatened, such as by caterpillar-eating birds. The larvae lift up the front of their body and tuck their head under, resembling the ancient Sphinx edifice in Egypt.
Larvae of sphinx moths are called hornworms because the eighth abdominal segment on most species has a thin, tapered spine on top. Otherwise, the larvae are smooth skinned without hairs or spines and commonly they are green and blend with foliage color. They have 3 prominent pairs of prolegs (fleshy appendages) in the middle of the abdomen and a pair at their rear end. Mature larvae of some species are over 3 inches long.
Adults are medium to large moths with a stout body. Adults of most species are nocturnal. They may not be observed except when drawn to lights at night and in the morning are found resting nearby. Some species are day active and can be observed feeding on flower nectar. Their mouthparts can be extended two or three times the length of their body to reach into deep flowers. Like a hummingbird adult, sphinx moths feed in flight and repeatedly extend and contract their mouthparts while feeding.
Eggs are commonly spherical and laid on foliage. Pupae occur in organic litter on the ground or in topsoil up to several inches below the surface.
Achemon sphinx moth. Eumorpha achemon is the most common sphinx moth that as larvae feeds on grapevines and Virginia creeper. The adult is present during late spring and again in midsummer. It is a nocturnal moth with a body length of up to 2 inches and a wingspan of 3 to 4 inches. The forewings are light brown to pinkish with gray and dark brown blotches. The hind wings are pink with a border and spots that are brown.
The spherical eggs are pale green and about 1/16 inch (1.5 mm) in diameter. They mostly occur singly on the top of older leaves.
Newly hatched larvae are green with a black anal horn. Mature larvae are brown or green and the horn disappears in the last instar. The mature larva is up to 3-1/5 inches long and has a yellow line along the upper body and whitish to yellow bars along the sides. The brown puparium (pupal covering) is about 2 inches long and occurs near the base of host plants just below the soil surface.
Big poplar sphinx. Pachysphinx occidentalis, also called western poplar sphinx, is the largest sphinx moth in California. The adult's body is about 2 inches long and the wingspan is up to 6 inches. Adults have 2 color forms; forewings are pale gray with brownish or dark grayish and brown. The hind wings are burgundy or purplish with shades of brown, gray, or both. The spherical eggs are green to whitish and about 1/16 inch in diameter.
Larvae are mostly green with lines or specks of white or yellow. Larvae grow up to 3 inches long and have a brown anal horn. They feed on various species of cottonwood, poplar, and willow.
Eyed sphinx. Smerinthus cerisyi, also called one-eyed sphinx or twin-spotted sphinx, is one of California's most common sphinx moths. It is often attracted to lights at night, especially late at night. The adult's body is 4/5 to 1-1/3 inches long with a wingspan of about 3 inches. The forewings are brown, gray, and tan as are portions of the hind wings. The hind wings also have rose pink. Each wing has a dark blue circle enclosing a whitish spot that resembles an eye.
Larvae are green and up to about 1-1/2 inches long. The anal horn is blue, pink, or yellow. The larvae feed on poplar and willow.
Snowberry clearwing sphinx. Hemaris diffinis, also called bumble bee moth, as an adult can be seen during the daytime in late spring and summer. The adult is 3/4 to 1 inch long and mostly shades of brown with blackish and yellowish. The wings are mostly clear with veins and a border that are brown.
Larvae are mostly green with lines of whitish, yellow, or both. The anal horn is black or green. Larvae grow up to 1-3/4 inches long. They feed mostly on snowberry (Symphoricarpus species) and other plants in the honeysuckle family (Caprifoliaceae).
Tobacco hornworm and tomato hornworm. Manduca sexta and M. quinquemaculata respectively, as larvae are thick, green caterpillars up to 4 inches long. Tobacco hornworm has white diagonal lines along the sides of the body and the anal horn is reddish. Tomato hornworm has white to yellow V-shaped lines along the side and the horn is commonly black. Both hornworms feed on Solanaceae such as eggplants, peppers, and tomatoes. The caterpillars are difficult to locate on their hosts and their chewing damage and dark frass (excrement) are commonly the first clues that hornworms are present.
The adults are mostly gray moths with black and white streaks and blotches. The body length is about 2-1/2 inches and the wingspan is up to 5 inches. The spherical egg occurs on foliage and is about 1/25 inch (1 mm) in diameter. It is green to whitish with a pearly appearance. The brown pupal covering occurs in organic litter on the ground or in a cell in topsoil up to several inches below the surface. It has a pitcherlike handle that holds the long mouthparts of the developing adult.
Whitelined sphinx. Hyles lineata, also called the striped morning sphinx, may be the most common sphinx moth in California. Its larvae feed on numerous host plants and are a sporadic pest of grapes. The adult is active in the late afternoon through dawn and can be observed feeding on nectar of flowering plants such as columbine, honeysuckle, larkspur, and salvia (sage). The forewings are mostly brown. They have distinct, lengthwise, white lines and a broad, pale brown to whitish band that runs from the base of the forewing to the tip. These markings are the source of its common name. The hind wings are brown and pink. The moths are 1 to 2 inches long with a wingspan of up to 4 inches.
Larvae grow up to 3-1/2 inches long and are commonly green, but there is also a black form. The green form has spots that are brown to reddish and yellow bordered by black. The black form has orange to yellow lines and spots. Both forms have an orange to yellow horn. The larvae feed on a wide variety of plants including caneberries, elderberry, evening primrose, fuchsia, grape, lilac, rose, and willowherbs. The pupal covering is shiny dark brown and up to 1-2/5 inches long.
Sphinx moths develop through four life stages: egg, larva, pupa, and adult. Overwintering is commonly as mature larvae or pupae in organic litter on the ground or below the surface of topsoil. In late winter or spring adults emerge from their pupal case, mate, and the females lay eggs.
Eggs are laid singly or in a loose group, varying by the species. When eggs are laid on the upper surface of leaves, commonly the hatching first instars chew a hole in the leaf and crawl through to the lower surface where they mostly feed.
The caterpillars may feed for about 1 month, varying by temperature and species. When mature, most larvae drop or walk down the plant to pupate on or in soil. Egg to adult development during the growing season takes about 2 months. Most sphinx moth species in California have 1 to 3 generations per year.
Sphinx moths as larvae chew and feed on foliage and occasionally on fruit. They are generally minor pests and typically do not warrant management. The caterpillars mature into beautiful moths that are important pollinators.
Naturally occurring parasitoid (parasitic) wasps appear to be a reason why the abundance of sphinx moths and their hornworm larvae are generally not damaging to plants. Where the larvae are present, feeding, and undesirable, they can be killed by snipping them in half with pruning shears or handpicking and disposing of them in the trash.
If caterpillars and their feeding damage are intolerably abundant, infested foliage can be thoroughly sprayed once or more with Bacillus thuringiensis (Bt) or spinosad. Spinosad is toxic to bees and certain beneficial predatory insects for at least several hours after the application; if applying it wait until the evening when honey bees are no longer active.
Adapted from California Insects and Grape Pest Management from the University of California Agriculture and Natural Resources, Common Name: Tomato Hornworm Scientific Name: Manduca quinquemaculata (Haworth) (Insecta: Lepidoptera: Sphingidae) from the University of Florida, and Integrated Pest Management for Tomatoes and Pests of the Garden and Small Farm: A Grower's Guide to Using Less Pesticide, University of California Statewide Integrated Pest Management Program (UC IPM).