Smerinthus ophthalmica
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Taxonomy
Order: Lepidoptera
Superfamily: Bombycoidea
Family: Sphingidae
Subfamily: Smerinthinae
Tribe: Smerinthini
Genus: Smerinthus
Species: ophthalmica Boisduval, 1855
Common Name(s): none
Notes: Synonymized with S. cerisyi until 2010.
Superfamily: Bombycoidea
Family: Sphingidae
Subfamily: Smerinthinae
Tribe: Smerinthini
Genus: Smerinthus
Species: ophthalmica Boisduval, 1855
Common Name(s): none
Notes: Synonymized with S. cerisyi until 2010.
General
Size: Wingspan 70-90 mm.
Distribution: Southern British Columbia and southern Alberta, south through Washington, Oregon, Idaho, western Montana, western Wyoming to northern California, northern Nevada, and northern Utah.
Habitat: Riparian, around larval host plants (also riparian).
Season: In the Bay Area, 3 distinct broods: March-May, June-August, and September-October.
Food: Adults do not feed; larvae feed on willow (Salix) and poplar (Populus).
Distribution: Southern British Columbia and southern Alberta, south through Washington, Oregon, Idaho, western Montana, western Wyoming to northern California, northern Nevada, and northern Utah.
Habitat: Riparian, around larval host plants (also riparian).
Season: In the Bay Area, 3 distinct broods: March-May, June-August, and September-October.
Food: Adults do not feed; larvae feed on willow (Salix) and poplar (Populus).
Life History
Egg
Oval, slightly flat, glossy, bright yellow, large for size of moth (Fig. 1a); become increasingly paler during development and may form a brown ring along the edge (Fig. 1b); prior to hatching, eggshell becomes translucent rendering larva visible; egg will appear a mottled greyish and yellowish white at this time (Fig. 1c).
Eggs are laid singly or in small groups on host leaves. Developmental time is usually about seven days at 20-24°C. If placed in the same container and not given proper ventilation in captivity, eggs will develop normally until a few days prior hatching but will turn brown and die — a phenomenon familiar to those who have hatched eggs of Citheronia regalis and other moths with large, thin shelled eggs. It is recommended when rearing to keep eggs thinly distributed in multiple airy containers for a high hatch rate.
Eggs are laid singly or in small groups on host leaves. Developmental time is usually about seven days at 20-24°C. If placed in the same container and not given proper ventilation in captivity, eggs will develop normally until a few days prior hatching but will turn brown and die — a phenomenon familiar to those who have hatched eggs of Citheronia regalis and other moths with large, thin shelled eggs. It is recommended when rearing to keep eggs thinly distributed in multiple airy containers for a high hatch rate.
Larva
First instar
When first hatched, body whitish yellow and slightly granulose; head capsule lusterless pale green and round with obvious cleavage line; horn red, straight, and short (about quarter length of the body); large for size of moth (4 mm) (Fig. 2a). With growth, body becomes pale green and granules become white and more visible; white subdorsal lines (starting from the head and merging diagonally into the horn), very faint white lateral diagonal stripes, and grey dorsal V-shaped stripes appear (best represented in Fig. 2e-f).
Larvae bite their way out of the eggshell and will initially rest for a few hours while their cuticle hardens and tans. Afterwards, the neonate larvae usually consumes the remaining eggshell, but they may begin feeding on host foliage immediately. Larvae prefer tender, growing shoots and often feed at the tip of leaves, working their way down (Fig. 2d-f), or sometimes from the edge, working their way to the center (Fig. 2c). They are solitary and rarely move except to feed, resting along the underleaf vein in a typical sphinx-like posture with only the last pairs of prolegs attached (Fig. 2e) for much of the day. Development time is five days at 20-24°C when feeding on growing shoots but can take as much as 10 days on tough, mature leaves.
Larvae bite their way out of the eggshell and will initially rest for a few hours while their cuticle hardens and tans. Afterwards, the neonate larvae usually consumes the remaining eggshell, but they may begin feeding on host foliage immediately. Larvae prefer tender, growing shoots and often feed at the tip of leaves, working their way down (Fig. 2d-f), or sometimes from the edge, working their way to the center (Fig. 2c). They are solitary and rarely move except to feed, resting along the underleaf vein in a typical sphinx-like posture with only the last pairs of prolegs attached (Fig. 2e) for much of the day. Development time is five days at 20-24°C when feeding on growing shoots but can take as much as 10 days on tough, mature leaves.
Second instar
Body bright green (may be slightly turquoise dorsally) and heavily covered in white granules; subdorsal lines and abdominal lateral diagonal stripes more obvious and slightly yellow (best represented in Fig. 3f); grey dorsal V-shaped stripes more obvious (Fig. 3d-e); head capsule now triangular and bordered by pale yellow inverted V; horn and thoracic legs either cream colored or pinkish (above figures show cream).
Larva behavior same as previous instar, but eat more frequently and are slightly more tolerate toward older leaves, though clear preference for younger leaves remains. Development time is extremely fast even at room temperature (20-24°C), taking about four days.
Larva behavior same as previous instar, but eat more frequently and are slightly more tolerate toward older leaves, though clear preference for younger leaves remains. Development time is extremely fast even at room temperature (20-24°C), taking about four days.
Third instar
Appearance similar to previous instar, but much greener body and turquoise head capsule; subdorsal lines and abdominal lateral diagonal stripes more obvious, especially where they merge with the horn; grey dorsal V-shaped stripes much fainter; thoracic legs pinkish. With growth, horn becomes bluer dorsally in the center (Fig. 4e); body becomes plumper (width becomes larger in relation to length) (Fig. 4f); body length reaches ~25 mm and body mass reaches 0.5-0.7 g.
Larvae feed much more aggressively during this instar and will consume mature and young leaves; however, they are still very particular about leaf freshness and quality (reject slightly wilted or yellowish leaves). larvae consume one leaf in its entirety before starting on a new leaf, staying in the same feeding area the whole time. Third instar development is rapid, growing noticeably larger every day and spending around six-seven days at 20-24°C.
Larvae feed much more aggressively during this instar and will consume mature and young leaves; however, they are still very particular about leaf freshness and quality (reject slightly wilted or yellowish leaves). larvae consume one leaf in its entirety before starting on a new leaf, staying in the same feeding area the whole time. Third instar development is rapid, growing noticeably larger every day and spending around six-seven days at 20-24°C.
Fourth instar
Appearance resembles previous instar but can be dimorphic in body color, being either yellowish-green or bluish-green (figures show yellowish green form); head capsule extremely large in relation to body size when freshly molted (Fig. 5a) with a much thicker and yellower inverted V and large red mandibles; horn becomes reddish or purplish blue, very short in relation to body length, and slightly curved back; spiracular circles become dark red; subdorsal lines and abdominal lateral diagonal stripes become well-defined and yellow, grey dorsal V-shaped stripes disappear. With growth, granules become smoother and more sparse (best represented in Fig. 5e-f); body becomes extremely plump and firm. Mature size is dependent on larval sex, with both sexes reaching about 70 mm in length but males smaller than females in mass; 3.8-4.3 g are likely male while 4.3-5.0 are more likely female. Mature larvae very similar to those of similar taxa such as S. cerisyi.
Smerinthus ophthalmica typically undergoes four larval instars instead of the typical five, making this the final instar. During the fourth instar, larvae feed extremely aggressively, stripping away several leaves a day, starting from the tip of the branch and working their way down. Unlike in previous instars in which larvae rested on the underleaf vein, fourth instar larvae are too large and must cling to the stem both when at rest and when feeding. When disturbed while resting, larvae will sometimes thrash around violently, but curiously, once habituated, will often wander around and began feeding again! Larva growth is tremendous (which compensates the absence of a fifth instar), tripling in body length and increasing in body mass by nine- to ten-fold from the beginning to end of the instar. Development time is rapid for this amount of growth, lasting around eight days at 20-24°C.
Smerinthus ophthalmica typically undergoes four larval instars instead of the typical five, making this the final instar. During the fourth instar, larvae feed extremely aggressively, stripping away several leaves a day, starting from the tip of the branch and working their way down. Unlike in previous instars in which larvae rested on the underleaf vein, fourth instar larvae are too large and must cling to the stem both when at rest and when feeding. When disturbed while resting, larvae will sometimes thrash around violently, but curiously, once habituated, will often wander around and began feeding again! Larva growth is tremendous (which compensates the absence of a fifth instar), tripling in body length and increasing in body mass by nine- to ten-fold from the beginning to end of the instar. Development time is rapid for this amount of growth, lasting around eight days at 20-24°C.
Prepupa
Once the fourth instar larvae are mature, they cease feeding, empty their guts, and begin wandering on the ground for one to two days as prepupae in search of a place to burrow and pupate. Criteria for where prepupae chose to burrow is unknown except that the soil or medium must be loose enough to do so. During this time, body color takes on an orange or brown undertone and body length shortens (Fig. 7a).
Once a pupation site has been found, they burrow beneath the surface and create a mud chamber in which to pupate. At this time, the prepupae become immobile as they prepare for pupation. In captivity, prepupae reach this immobile state regardless if any medium is provided in which to burrow. While immobile, body becomes firm and contracted; dirty brown coloration becomes increasingly prevalent, especially around the thorax; horn color dulls and becomes slightly translucent; intersegmental grooves become deeper; prolegs become contracted (Fig. 7b [extracted from mud chamber]).
Hours before pupation, body color dulls into a dirty greenish-yellowish-brown and is speckled with brown spots; head capsule, thoracic legs, and horn become dull and translucent (internally empty); cuticle becomes very loose and wrinkled (Fig. 7c).
Once a pupation site has been found, they burrow beneath the surface and create a mud chamber in which to pupate. At this time, the prepupae become immobile as they prepare for pupation. In captivity, prepupae reach this immobile state regardless if any medium is provided in which to burrow. While immobile, body becomes firm and contracted; dirty brown coloration becomes increasingly prevalent, especially around the thorax; horn color dulls and becomes slightly translucent; intersegmental grooves become deeper; prolegs become contracted (Fig. 7b [extracted from mud chamber]).
Hours before pupation, body color dulls into a dirty greenish-yellowish-brown and is speckled with brown spots; head capsule, thoracic legs, and horn become dull and translucent (internally empty); cuticle becomes very loose and wrinkled (Fig. 7c).
Pupa
Teneral pupae bright, translucent green (Fig. 7a); becomes increasingly browner upon melanization ("tanning") of cuticle (Fig. 7b); hardened pupae glossy black with dark purple intersegmental grooves (Fig. 7c). Overall shape relatively narrow; tapered posteriorly; cremaster pointy; wings elongated at tips; legs stout; proboscis absent.
Female pupa mass average about 3 g; male mass about 2.5 g. Very large for size of larva, retaining about 70% of peak larva mass while in many other species, pupa retain just 40-50% of peak larva mass. This high pupa retention of larva mass, along with the large egg size of this species, seems to compensate for the absence of a fifth instar in obtaining the adult size.
Female pupa mass average about 3 g; male mass about 2.5 g. Very large for size of larva, retaining about 70% of peak larva mass while in many other species, pupa retain just 40-50% of peak larva mass. This high pupa retention of larva mass, along with the large egg size of this species, seems to compensate for the absence of a fifth instar in obtaining the adult size.
Adult
The adults display a full color range between tan and grey, with intermediate ones brown. (Fig. 8g). Forewing very narrow with pointed tips; edge wavy; various shades of grey and brown, with the basal, antemedial, and subterminal areas lighter, and medium and terminal areas darker; latter two areas also have a portion of brown posteriorily (that matches color of thorax center). Underside is marked with reddish pink (Fig. 8i). Hindwing small and narrow; primarily dark pink starting from the base and blends into grey or brown near the margin; marked with a conspicuous blue eyespot outlined with black, with a large black pupil in the center (Fig. 8b-e). Eyes black; antennae white with brown pectinations (larger in males); no probacis. Thorax large and furry; brown in center, light grey or sometimes pink (usually vibrantly colored tan forms) on sides. Abdomen plump in females with large ovipositar (Fig. 8c), narrower and curved upwards in males (Fig. 8f).
This large hindwing eyespot serves as an identifying trait among other Sphingidae. Males of S. ophthalmica are said to be distinguishable from those of S. cerisyi due to their smoother forewing edges and small differences in forewing pattern. Females cannot be distinguished based only on appearance. Tan forms exist in S. ophthalmica and not in S. cerisyi.
Eclosion occurs in the evening. Males take flight immediately, while females remain near their eclosion site until mated. They are strong fliers with extremely rapid wing movement. At rest, the forewings usually cover most of the hindwings, but once disturbed the forewings are spread to reveal the intimidating hindwing eyespots as a defensive measure against predators. Adult lifespan is short, lasting 1-2 weeks.
This large hindwing eyespot serves as an identifying trait among other Sphingidae. Males of S. ophthalmica are said to be distinguishable from those of S. cerisyi due to their smoother forewing edges and small differences in forewing pattern. Females cannot be distinguished based only on appearance. Tan forms exist in S. ophthalmica and not in S. cerisyi.
Eclosion occurs in the evening. Males take flight immediately, while females remain near their eclosion site until mated. They are strong fliers with extremely rapid wing movement. At rest, the forewings usually cover most of the hindwings, but once disturbed the forewings are spread to reveal the intimidating hindwing eyespots as a defensive measure against predators. Adult lifespan is short, lasting 1-2 weeks.
Mating & oviposition
Females release pheromones from their ovipositar ("call") around midnight to attract males. Once in copula (Fig. 9a-b), the partners will remain paired until the following evening, though the actual copulation was likely accomplished shortly after pairing. After mating, males will continue to seek mates, while females seek host plants (Salix and Populus) on which to oviposit. A single female usually has around 200-300 eggs fully developed in her abdomen upon eclosion, and usually lays just a few eggs per host before moving onto another area.
Authors
Alan Liang
Alan Liang
