Smerinthus populi ferruginea-fasciata Gillmer, 1904
Smerinthus populi ferruginea Gillmer, 1904
Smerinthus populi fuchsi Bartel, 1900
Smerinthus populi grisea-diluta Gillmer, 1904
Smerinthus populi grisea Gillmer, 1904
Smerinthus populi pallida-fasciata Gillmer, 1904
Smerinthus populi rectilineata Klemensiewicz, 1912
Smerinthus populi rufa-diluta Gillmer, 1904
Smerinthus populi rufa Gillmer, 1904
Smerinthus populi rufescens (de Selys-Longschamps, 1857)
Smerinthus populi rufescens Fuchs, 1889
Smerinthus populi subflava Gillmer, 1904
Smerinthus populi violacea Newnham, 1900
Adults may be seen from May to September, and do not feed, not having a functional proboscis, and can vary in colour from grey to yellow. The larva is green, feeds on poplar and some other tree species, and pupates below ground.
Laothoe populi is a large (wingspan 70–100 mm (2.8–3.9 in)), odd-looking species of moth, due to its habit of resting with its hindwings held further forward than (but still half hidden by) the forewings. The species lacks a frenulum joining the wings together, and is said to look like a cluster of dead leaves of the main host, poplar.
When disturbed, the moth will suddenly reveal a bright orange-red basal patch on the hindwing, possibly as a distraction or startle display. The wings are grey marked with darker grey fascia but with the greys occasionally replaced by buffish tones, a form more frequent among females than males. There is a white spot at the distal edge of the cell on the forewings.
One or two broods are produced each year and adults can be seen from May to September. The adults do not feed. The species overwinters as a pupa.
The egg is large, spherical, pale green, and glossy, and is laid singly or in pairs on the underside of leaves of the host plant. Females lay up to 200 eggs.
On first hatching the larva (or "hornworm") is pale green with small yellow tubercules and a cream-coloured tail horn. Later, it develops yellow diagonal stripes on its sides, and pink spiracles. Individuals feeding on willows may become quite heavily spotted with red. Others are more bluish white with cream stripes and tubercules. They are stout bodied, and grow to 65–85 mm (2.6–3.3 in).
The larva pupates in an earthen cell 2–3 cm (0.79–1.18 in) below the surface, near its host plant. It has a short cremaster.
Although they emerge late at night or early in the morning, the moth flies starting from the second night and is strongly attracted to light. Having no functional proboscis, it does not feed.