The white-lined sphinx moth, scientifically known as Hyles lineata, is a fascinating insect belonging to the family Sphingidae. Recognizable by its stout, furry body and distinctive wing patterns, this moth is a common sight throughout North and Central America, and even parts of South Asia. Its life cycle, like that of many Lepidoptera, involves a dramatic transformation from a voracious caterpillar to a nectar-sipping adult. Understanding the dietary habits of both the larval and adult stages is crucial to appreciating the moth's ecological role and its interactions with various plant species.
Identifying the White-Lined Sphinx Moth
Hyles lineata has a wide geographic range, from Central America to southern Canada, through Mexico, and most of the United States. Some regions of South Asia, like Sindh, Pakistan, are reported to have habitats for these moths. The adult moth has a wingspan of 2 to 3 inches and a stout, furry body. The dorsal hind region is crossed by six distinct white stripes, with similar striping patterns on the wings. The forewing is dark brown with a tan stripe extending from the base to the apex. White lines cover the veins. The black hindwing features a broad pink median band.
Larvae exhibit wide variation in color. They can be black with orange spots arranged in lines down the whole body.
The Caterpillar's Varied Appetite
The caterpillar stage of the white-lined sphinx moth is characterized by an incredibly diverse diet. These larvae are ardent eaters, consuming a wide range of host plants. In the spring, adult females lay eggs on various plants, providing a food source for the emerging larvae. Caterpillars overwinter and can emerge between February and November, when they begin to feed.
Some of the plants that serve as food sources for white-lined sphinx moth caterpillars include:
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- Apples
- Evening primrose (Oenothera spp.)
- Four-o’clocks (Mirabilis jalapa and M. nyctaginea)
- Fuchsia
- Gaura lindheimeri (pink guara)
- Grape
- Pentas
- Purslane
- Tomato
- Willow-weed (Epilobium)
- Elderberries
- Lilac
- Rose
Caterpillars feed on a large variety of plant parts, including the leaves, green fruits, and even stems. They have even been observed feeding on the flowers of pink guara (Guara lindeimeri). In some instances, they have been found consuming spotted spurge, a noxious weed.
The caterpillars' ability to consume such a wide variety of plants can sometimes lead to them being considered pests. In large numbers, they are capable of wiping out entire fields of plants. However, in smaller numbers, they can be beneficial in promoting bird and reptile populations. Regular monitoring of plants is key to protecting them from caterpillar damage.
The Adult Moth's Nectar Preference
In contrast to the caterpillar's broad diet, adult white-lined sphinx moths primarily feed on nectar from flowers. Like hummingbirds, they hover around flowers, using their long proboscis to drink nectar. They are common pollinators.
The adults will feed on different flowers depending on the time of day. At night, they prefer white or pale-colored flowers, which are easier to identify against the dark foliage. During the day, they may visit brightly colored flowers. Some of the flowers that white-lined sphinx moths frequent include:
- Cardinal flower (Lobelia cardinalis)
- Columbine (Aquilegia)
- Evening primrose
- Honeysuckle
- Hosta
- Jimson weed (Datura meteloides)
- Lilac
- Penstemon
- Petunia
- Phlox
- Coyote mint flower (Monardella odoratissima)
A study from the 1970s focused on H. lineata nectar feeding patterns in Emerald Lake, Colorado, specifically on Aquilegia coerulea flowers. The study identified two groups of moths: one with patches of pollen near their eyes and one with no detectable pollen. The moths with no pollen had significantly longer tongues. This suggests that within H. lineata, tongue length may influence foraging behavior and pollination effectiveness.
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The White-Lined Sphinx Moth as a Pollinator
Hawk moths, including H. lineata, are considered long-tongued nectar foragers. The annual presence of H. lineata populations selects for whiter flowers. This highlights the moth's role in shaping flower morphology through pollination.
Life Cycle and Behavior
Adults typically do not survive cold northern winters, but larvae overwinter and moths begin to appear in mid-May. Depending on abundance, a second flight may occur in late August or early September. When preparing to transition into the pupal stage, caterpillars dig shallow burrows in the ground where they then stay for 2 to 3 weeks, at which point they emerge as adults.
Hyles lineata prefer flying at night but also sometimes fly during the day. Though hawk moths can be both diurnal or nocturnal (or both), they all have three spectral receptors that are sensitive to blue light, green light, and ultraviolet. Vision is a key component of H. lineata physiology, and they also have strong olfactory capabilities.
Observations and Population Dynamics
Record levels of precipitation and snowpack can lead to spectacular wildflower blooms, benefitting pollinators like the white-lined sphinx moth. In 2023, many white-lined sphinx moths were observed feeding on penstemons in Kings Canyon National Park. Observations of these moths reported in iNaturalist in 2023 were higher than in the previous five years combined, with more than one-third of all California iNaturalist records occurring in 2023.
Conservation and Supporting Moth Populations
Like other pollinators, butterflies and moths face threats, including loss of habitat, exposure to pesticides, diseases, and invasive species. Moths are also threatened by light pollution from outdoor lighting.
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To support moths in your landscape:
- Minimize the use of pesticides.
- Provide shelter in the form of leaf litter and small brush piles.
- Provide food for larval stage and adult moths.
- Incorporate light-colored blooms and fragrant native forbs in your landscape.
Historical Use as Food
The caterpillars have been (and in some places still are) gathered and eaten by Native Americans. The Cahuilla and Tohono O’odham collected nearly mature caterpillars feeding on sand verbena and other plants in the Southern California and Sonoran deserts. They pulled off the head and jerked out the guts, then placed the larva in a bag or basket. In the evening the insects were roasted, skewered on a stem, for a feast.