Large Moths

authored by GVM resident Terry W. Campbell, BS, MS, DVM, PhD

Sphynx moth
A White-lined Sphynx moth trapped in the author’s house that was eventually caught and released.

White-lined Sphynx moth (Hyles lineata)

At first glance, one may think that a hummingbird has become trapped in the house as it flitters about between the shades and the window pane. Later in the evening and the darkness of the house, it becomes attracted to lights. This could be a White-lined Sphynx moth (Hyles lineata). (Image 1)

The wingspan of White-lined sphinx moths measures between 2.5-3.5 inches (6.3 and 9.0 cm) making them one of the largest moths found in Colorado. The fore wing is generally dark olive brown to gray with a strong white lengthwise band running through the center giving the moth its common name. Smaller white veins cross the wing. The hind wing is dark gray-black with a central pink area.

White-lined sphinx moths have extractable long tube-like mouthparts for feeding on nectar; therefore, they are often found hovering over deeply-lobed flowers, just like hummingbirds. In fact, they are frequently referred to as “Hummingbird moths.” Others refer to these heavy bodied moths as “Hawk moths” or simply “Sphinx moths.”

There are over 30 species of this type of moth in Colorado; however, the White-lined sphinx moth is the species most commonly observed in this habit (GVM). Although it can be seen feeding on flowers during the day, it is usually most active during late afternoon and at dusk.

The eggs of this species of moth are laid singly on a wide variety of host plants. Evening primrose (Oenothera sp.) and purslane (Portulaca sp.) are the most common hosts in the moth’s home range, but larvae have been found developing on many other plants. The caterpillars (larvae) of this moth are extremely variable in coloration and patterning. Predominantly greenish forms are marked with yellow, black and red. Very dark, nearly black forms also can occur, which have yellow markings. Yellow forms also exist. Full-grown caterpillars may be nearly 3 inches long and have a prominent flexible spine (horn) on the tip of the abdomen (hind end); typical of most other hornworms. A full-grown caterpillar migrates from its host plant and digs a small chamber in the soil a few inches below the surface where it will pupate. The pupae are typically brown and two inches or more in length.

It should be mentioned that the most widely recognized hornworms and most infamous are those that feed on tomatoes – the tomato hornworm (Manduca quinquemaculata) and the tobacco hornworm (Manduca sexta), two species considered as garden pests. However, the majority of the more than 30 hornworm species found in Colorado, including the White-lined sphinx moth caterpillar, are rarely observed and do not cause significant injury to plants.

 Columbia Silk moth (Hyalophora Columbia gloveri)

Silk moth
A Columbia Silk moth found on the front porch of the GVM office.

Another moth in our area is even larger. It is a giant silk moth called Columbia Silk moth (Hyalophora columbia gloveri) with a wingspan that measures between 4.3 and 5.9 inches (11-15 cm). The wingspan of the one in the photo measured 4.5 inches (11.4 cm). They are distantly related (as in same superfamily) to the Asian silkworms whose cocoons produce silk for fabric. They resemble the Cecropia Silk moth (Hyalophora cecropia) which is the largest native moth in North America and lives at a lower elevation. Columbia Silk moths can be found in a wide variety of wooded habitats from Alberta (Canada) and Montana south through the Rocky Mountain region to southwest Texas and into central Mexico.

The wings of this moth are dark brown to red-brown. The gray area outside the white postmedian band does not contain any red. Crescent spots on the forewings and hindwings are white, although occasionally the spots on the forewing may be reduced or absent. The large eyespots on the wings deflect attacks from birds.

Adult Columbia Silk moths have no mouthparts; therefore, they do not feed. They live for only about a week, long enough to reproduce. Females lay one or two eggs at the base of the needles, leaves, and twigs of host plants. The eggs hatch in about 2 weeks and the solitary caterpillars feed on a variety of trees and shrubs, such as, Western choke cherry (Prunus demissa), Bitter cherry (P. emarginata), Bitterbrush (Purshia tridentata), wild roses (Rosa sp.), willows (Salix sp.), Buffalo berry (Shepherdia argentea), Russian olive (Eleagnus angustifolius), and buckbrush (Ceanothus sp.).

The caterpillars overwinter in heavily woven, compact, double-layered silk cocoons close to the ground on the trunks or stems of their host plant (trees or shrubs) or on nearby thick undergrowth. They emerge as adults in April to June.

Suggested reading

Butterflies and Moths of North America:

Cranshaw W. 2014. Hornworms and “Hummingbird Moths.” Colorado State University Extension, Fact sheet No. 5.517, Insect Series- Home and Garden