Hummingbird moths are a fascinating group of insects that look and act very much like hummingbirds as they visit flowers. There are over 140 species of hummingbird moths in the family Sphingidae, and they can be found all over North and South America (1). Hummingbird moths beat their wings up to 70 times per second, allowing them to hover in place as they unfurl their long proboscis and drink nectar from flowers (2). This behavior, along with their slender bodies and long beaks, gives them an uncanny resemblance to hummingbirds. While hummingbirds only visit flowers during the day, many hummingbird moth species are nocturnal or crepuscular, visiting flowers at dawn or dusk instead (3).
One of the most interesting parts of the hummingbird moth’s life cycle is its relationship with host plants for laying eggs. Female hummingbird moths will seek out specific plants, often in the families Solanaceae, Lythraceae, Oleaceae, and Rubiaceae, to lay their eggs on (4). The caterpillars that emerge feed exclusively on the leaves of the chosen host plant. Different hummingbird moth species have preferred host plant groups that their caterpillars are specialized to eat (5). Understanding which plants hummingbird moth caterpillars feed on can provide clues into hummingbird moth ecology and behavior.
Main host plant families
There are four plant families that make up the majority of host plants for hummingbird moth caterpillars in North America:
Solanaceae (nightshade family)
Many hummingbird moths preferentially lay eggs on plants in the nightshade or Solanaceae family, which includes over 2,000 species such as peppers, tomatoes, potatoes, eggplants, and tobacco (6). Important Solanaceae host plants for hummingbird moths include:
- Tomatoes (Solanum lycopersicum)
- Potatoes (Solanum tuberosum)
- Tobacco (Nicotiana tabacum)
- Petunias (Petunia hybrida)
- Jasmine tobacco (Nicotiana alata)
- Jimsonweed (Datura stramonium)
Some of the hummingbird moth species that use Solanaceae as hosts include the white-lined sphinx (Hyles lineata), the wild cherry sphinx (Sphinx drupiferarum), the Virginia creeper sphinx (Darapsa myron), and the pandorus sphinx (Eumorpha pandorus) (7).
Lythraceae (loosestrife family)
The Lythraceae or loosestrife family, containing 32 genera and over 600 species, is another important host plant family for hummingbird moths (8). Genera used include Lagerstroemia, Lytthrum, Cuphea, and Decodon. Specific Lythraceae hosts include:
- Crepe myrtle (Lagerstroemia indica)
- Purple loosestrife (Lythrum salicaria)
- Clammy cuphea (Cuphea viscosissima)
Hummingbird moth species that use Lythraceae plants are the Lethe eurydice, the twin-spotted sphinx (Smerinthus jamaicensis), and the Ibanora sphinx (Cocytius antaeus) (9).
Oleaceae (olive family)
The olive or Oleaceae family contains over 600 species of trees, shrubs, and vines like lilacs, ash trees, and jasmine (10). Important members of this family for hummingbird moths include:
- Lilacs (Syringa vulgaris)
- Ash trees (Fraxinus spp.)
- Privet (Ligustrum vulgare)
- Jasmine (Jasminum spp.)
Hummingbird moths that use Oleaceae as caterpillar hosts include the Lethe portlandia, the snowberry clearwing moth (Hemaris diffinis), and the white-lined sphinx (Hyles lineata) again (11).
Rubiaceae (madder family)
Containing over 13,000 species, the Rubiaceae or madder family is best known for plants that produce the stimulant chemical caffeine, like coffee (Coffea spp.) and gardenia (Gardenia jasminoides) (12). Other important Rubiaceae genera used by hummingbird moths are Galium and Hamelia. Known Rubiaceae hosts include:
- Buttonbush (Cephalanthus occidentalis)
- Coffee (Coffea spp.)
- Waxyleaf privet (Ligustrum japonicum)
- Bedstraw (Galium)
Some Rubiaceae-feeding hummingbird moths are the white-lined sphinx (Hyles lineata), the wild cherry sphinx (Sphinx drupiferarum), the Lethe anthedon, and the snowberry clearwing moth (Hemaris diffinis) (13).
Other plant families
While Solanaceae, Lythraceae, Oleaceae, and Rubiaceae make up a large proportion of host plants, some hummingbird moths use species from other plant families:
Apocynaceae (dogbane family)
- Periwinkle (Vinca minor)
- Oleander (Nerium oleander)
Bignoniaceae (bignonia family)
- Catalpa (Catalpa bignonioides)
Caprifoliaceae (honeysuckle family)
- Honeysuckles (Lonicera spp.)
- Snowberry (Symphoricarpos albus)
Convolvulaceae (morning glory family)
- Sweet potato (Ipomoea batatas)
Ericaceae (heath family)
- Rhododendron (Rhododendron spp.)
- Blueberry (Vaccinium spp.)
Fabaceae (pea family)
- Wisteria (Wisteria spp.)
- Kudzu (Pueraria montana)
Malvaceae (mallow family)
- Hibiscus (Hibiscus spp.)
Salicaceae (willow family)
- Poplars (Populus spp.)
- Willows (Salix spp.)
Vitaceae (grape family)
- Grapes (Vitis spp.)
Preferred host plants by hummingbird moth species
While many hummingbird moth species are generalists and will use plants from several families, others have very specialized requirements and will only use one or two host plant species. Here are some examples of specialists:
White-lined sphinx moth (Hyles lineata)
The white-lined sphinx moth is one of the most generalist North American species. Its caterpillars feed on over 50 host plants including:
- Apple (Malus domestica)
- Elm (Ulmus spp.)
- Grape (Vitis spp.)
- Tomato (Solanum lycopersicum)
- Plum (Prunus spp.)
- Poplar (Populus spp.)
- Willow (Salix spp.)
Wild cherry sphinx (Sphinx drupiferarum)
As the name suggests, this species strongly prefers cherry (Prunus spp.) as a host:
- Chokecherry (Prunus virginiana)
- Black cherry (Prunus serotina)
It will sometimes use other trees like apple, elm, birch, poplar, and willow.
Big poplar sphinx (Pachysphinx modesta)
The big poplar sphinx lives up to its name and restricts itself to poplar and cottonwood (Populus spp.) hosts, especially:
- Eastern cottonwood (Populus deltoides)
- Balsam poplar (Populus balsamifera)
Virginia creeper sphinx (Darapsa myron)
This sphinx moth primarily uses Virginia creeper (Parthenocissus quinquefolia) and grape (Vitis spp.) as caterpillar hosts.
Azalea sphinx (Darapsa choerilus)
The azalea sphinx, as you may have guessed, feeds its caterpillars almost exclusively on azalea and rhododendron (Rhododendron spp.).
Ello sphinx (Erinnyis ello)
Also known as the pineapple sphinx, this species feeds solely on pineapple (Ananas comosus).
Catalpa sphinx (Ceratomia catalpae)
This sphinx is restricted to using catalpa (Catalpa spp.) as its caterpillar host plant.
Bumblebee moth (Hemaris diffinis)
Despite its wide range, the bumblebee moth caterpillar has an extremely narrow diet of just two host plants:
- Snowberry (Symphoricarpos albus)
- Honeysuckle (Lonicera spp.)
Hummingbird moths as pollinators
The co-evolution between hummingbird moths and their host plants has shaped some fascinating ecological relationships. As the moths visit host plant flowers to drink nectar, they also serve as important pollinators. Some plants even appear to have flowers adapted specifically to pollination by hummingbird moths (14).
Deep tubular flowers are perfect for the moths’ long proboscis. Many host plants like petunias, jasmine, honeysuckle, and catalpa offer lots of nectar at the base of tubular blossoms. The moths’ hover-and-sip behavior leads to more effective pollen transfer than by short-tongued bees. As a reward, the moths get an excellent nectar source near their caterpillar host plants. It’s a win-win situation for both parties.
Research in California found that the Catalpa sphinx moth was the most effective pollinator of its host plant, western catalpa (Catalpa speciosa). The moth’s behavior led to higher catalpa fruit and seed production compared to other pollinators like bees. Their coevolved relationship benefits both moth and plant (15).
Understanding these ecological partnerships can help us boost populations of declining pollinators like hummingbird moths. Providing host plants that offer nectar resources is crucial habitat for both adult and juvenile moths. Supporting these important plant-pollinator relationships will keep America’s gardens buzzing with life.
Conclusion
Hummingbird moths display amazing adaptations like hover-feeding that allow them to take advantage of tubular blossoms. Their life cycle intimately connects them to host plants that their caterpillars rely on. While they use a diversity of plant families, the Solanaceae, Lythraceae, Oleaceae, and Rubiaceae make up a large proportion of hummingbird moth hosts. Different species show preferences ranging from extreme specialization on one plant, to using dozens of host species across many families. Understanding these ecological relationships can help us support both hummingbird moths and their plant partners that benefit from their expert pollination services. Providing the right mix of host and nectar plants will attract these captivating moths to gardens across North America.
