Parnassius smintheus, the Rocky Mountain parnassian[1], or Rocky Mountain apollo[2], is a high-altitude butterfly found in the Rocky Mountains throughout the United States and Canada. It is a member of the snow Apollo genus (Parnassius) of the swallowtail family (Papilionidae). The butterfly ranges in color from white to pale yellow-brown, with red and black markings that indicate to predators that its body contains chemicals that make it distasteful to eat.[3]
| Rocky Mountain parnassian | |
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| Species: | P. smintheus |
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| Parnassius smintheus Doubleday, [1847] | |
The Parnassius smintheus primarily feed on the leaves of the Sedum lanceolatum plant as larvae and on its nectar as adults. The butterfly tends to reside in meadows, and avoids forests, because it strongly prefers light. The males of this species fly from meadow to meadow frequently to find females and food resources, whereas females are more likely to avoid flying.[4] The males seem to have mate choice in this species, as they emerge from the pupae earlier than the females and patrol for females, heavily preferring newly emerged females that have not yet flown.[5]
Although the Parnassius smintheus populations are not endangered yet, due to climate change and human activity, there has been a decrease in viable habitats in the last few decades for the species that is projected to continue in the future.[6]
Range and Habitat
The range of the butterfly is based primarily in the Rocky Mountains, which spans Canada and the United States.[4] This includes the mountainous areas of Yukon, Alaska, and British Columbia in Canada, and south as far as New Mexico in the United States.[1]
Parnassius smintheus can often be found in alpine and subalpine meadows. It was found that males of this species preferred meadows with a greater abundance of nectar flowers and a higher quantity of the host plant Sedum lanceolatum. They also preferred meadows with a greater number of females of their species. Males may sample two or more meadows to gain information on their relative quality. In contrast, the female butterflies showed no preference for meadows with more nectar flowers or the host plant, or for greater number of males. It has been suggested that males may prefer meadows with greater food sources more than females do due to needing more energy for greater flights and energy demand.[4]
Food Resources
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The primary larval host plant is Sedum lanceolatum. Sedum lanceolatum is a yellow-flowered perennial succulent common in rocky habitats in Western North America.[2] Larval foodplants may less frequently include other stonecrop species, including S. divergens, S. oreganum, S. stenopetalum, and S. integrifolium.[3] The foodplants tend to grow most abundantly on steep, well-drained, gravelly slopes. They can mostly be found 20-40 meters above the tree-line.[7] Herbivores feeding on S. lanceolatum is rare, because it produces a deterrent cyanoglycoside, sarmentosin, so Parnassius smintheus larvae are infrequently accidentally preyed upon as a result of the foodplant being ingested. The larvae also sequester sarmentosin from the plant for their own defense. However, it has been found that if the S. lanceolatum plant becomes physically damaged by mechanical means, the larvae feeding on it have reduced growth rates, possibly due to an induced defense by the plant itself. While damage by insects does not cause plant defense[2], damage from feeding by the larvae does induce defense by the plant. Consequently, the larvae often hurry to feed, then switch to another host plant within the time window offering high nutritional quality. Larvae will typically feed and leave a plant in less than half an hour.[8] From November to February, the leaves of their foodplant are fatally toxic to the larvae, but for the rest of the year, the larvae feed and develop normally. If the snow melts before March, the eggs hatch while the larval foodplant is still toxic, and the larvae perish.[3]
Life cycle
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Egg
The eggs of Parnassius smintheus are white and round, but flattened at the top and bottom. They exhibit a pebbled surface, while the micropylar area is brown and sunken.[3] The surface of the egg is generally more sculptured compared to the eggs of other butterflies, likely due to the thick chorion that evolved to protect the overwintering egg from predators, parasitoids, and adverse environmental conditions.[9] Around 75 eggs are produced per female.[10] The eggs are generally laid on the underside of flower heads, leaves, sticks, stones, moss, clumps of dirt, and sometimes on the larval foodplant. The female may or may not oviposit on the foodplant itself, and may sometimes lay her eggs quite far from the plant. The embryo develops into first instar larva within a month of oviposition but the egg does not hatch until the snow melts the next spring.[3]
Larvae
The first instar larva has a black body with many hairs, and a dull black head.[3] The larvae complete five instars before pupating.[2] The fifth instar larva is black, with many short fine black hairs littered over its body. It sports two lateral and two dorsal rows of bright yellow spots. It has small and pale yellow vestigial osmeteria. Since they may not always hatch close to their foodplant, the larvae have a fast, directional search pattern. They tend to feed rapidly on their larval host plant, then move to a basking location on open ground up to a few meters away for thermoregulation.[3]
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Pupae
The pupae of the Parnassius smintheus are dark yellow brown to red brown and formed in a weak cocoon in litter on the ground.[3]
Adults
The Parnassius smintheus butterflies are generally translucent yellowish white with black, grey, and red markings, though they vary heavily in color.[3] They have a wingspan ranging from 2 to 3 inches. The dorsal forewing exhibits a marginal grey band and a weakly developed pale grey submarginal band. The margin of the forewing usually has small triangles of black at each vein running through the wing, as well as some grey markings. The ventral hindwing may also have marginal and submarginal grey markings. The fringes of the wings are typically black at then ends of the veins. The hairs and scales on the heads, legs, and ventral abdomen are usually yellowish. Both sexes usually have bright red spots on the hindwings and forewings. Populations residing at higher elevations typically have darker females, and both males and females are smaller at low elevations.[3] Adult butterflies of this species feed predominantly on the nectar of yellow-flowered species including Potentilla fruticosa, Solidago multiradiata, Senecio canus, and S. lanceolatum[4].
Subspecies
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Listed alphabetically.[11]
- P. s. magnus Wright, 1905 The submarginal band of the forewing is almost complete but less sharply marked than in behrii, and the glassy border is broader, extending to the hinder angle and less restricted by white marginal spots: hindwing in the type-specimen without anal and submarginal spots, the anterior ocellus very small, the posterior one also only moderately large, the latter with white pupil, the former entirely red; female with costal spots copiously filled in with red and red-dotted hindmarginal spot on the forewing, blackish shading in the disc, border broadly glassy grey; ocelli of the hindwing large, the posterior one with white pupil, submarginal band not extra strongly marked, but the margin itself glassy. Washington State
- P. s. olympiannus Burdick, 1941 Olympic Mountains, Vancouver Island
- P. s. pseudorotgeri Eisner, 1966 Colorado (San Juan Mountains)
- P. s. sayii Edwards, 1863 The males are usually larger, with larger deep red ocelli; in the females a more copious sprinkling with black scales; the costal spots of the forewing are large and quite filled in with red, the glassy border broad, only separated from the submarginal band by a row of luniform spots, the submarginal crescents of the hindwing especially strongly marked and merged into a broad band.
- P. s. smintheus Doubleday, [1847]
- P. s. sternitzkyi McDunnough, 1936 North California
- P. s. xanthus Ehrmann, 1918 Washington State
- P. s. yukonensis Eisner, 1969 South Yukon, British Columbia
Similar species
- Clodius parnassian (P. clodius)
- Eversmann's parnassian (P. eversmanni)
Local Dispersal
Immigration and emigration of the Parnassius smintheus into different meadows increases when there is greater connectivity of the meadows. There is greater immigration to larger populations in general, while emigration from large populations tends to be low. This trend is probably related to mating opportunity.[7] Parnassius smintheus tend to avoid forest edges and show lower migration rates into different meadows in a forest habitat. They also tend to fly less often and at lower rates in forests than in meadows, most likely due to lower light levels.[6] It was found that the total distance moved by both flying and crawling was significantly greater in meadows than in forests, though the distances moved by crawling were generally limited to less than 2 meters. Since the butterflies avoid forest edges, meadows surrounded by forest will experience lower immigration and emigration rates.[12]
Protection
The Parnassius smintheus butterflies have a strong odor and excrete from their anus brown fluid that smells like their body when attacked. Their body fluid is a nasal irritant to humans. Their white wings with black and red markings warn of their unpalatability to birds, while their odor serves to warn rodents off. Males most likely have more distasteful compounds in them than females, because chipmunks tend to eat more females than males of this species.[3]
Mating
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Mate Searching Behavior
Males of this species often have poor visual discrimination, so they investigate all flying or sitting objects of the approximate size and color of the females of their species. They primarily identify female Parnassius smintheus by their light color, so they are as likely to chase small blue lycaenids as they are to chase large white butterflies, but tend to ignore darker butterflies like fritillaries.[3] The males emerge from their pupae before females do in order to patrol for newly emerged females over a large area.[5] They patrol by flying over large areas then investigating any resting or flying females after spotting them. Males fly long distances continuously in search of females, stopping only to bask or feed.[3]
Mate Choice
Male Parnassius smintheus often mate with young females, preferring females who have not yet expanded their wings. The females of this species only mate once, lay eggs only once, and mature their eggs throughout their life, so the youngest females have the greatest potential fitness, and are selected for by males. There is also evidence that females emit a pheromone produced during its pupal stage, but its effect diminishes with time. The window of opportunity for a female to mate appears to be rather short, limited to only about three days.[5] The females of this species are not guaranteed to mate, as it has been estimated that around 14% of females never mate. Female mating success is correlated with population size, where reduced female mating success was observed at low population densities, and greater success at higher population densities. However, other studies have suggested that female mating success decreases as density increases, possibly due to male-male competition for mating.[10]
Courtship
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Parnassius smintheus exhibits no courtship. Males dive on a female upon finding her and force her down to the ground if she is not already there, and forcibly attempt to mate. This is successful if she has not already already mated, but usually unsuccessful if she has already mated, due to a sphragis structure. Unsuccessful matings may last an hour or more before the female escapes. If a female is unreceptive to mating, the butterfly may close up their wings tightly when a male approaches to attempt to avoid being seen.[3]
Nuptial Gifts
After copulation, the male Parnassius smintheus deposits an waxy genital plug placed on the tip of the female's abdomen called a sphragis to prevent the female from mating again.[3] It contains the sperm and important nutrients for the female.[13] This also ensures that the male is the only one to fertilize the female’s eggs. Occasionally, the sphragis is not properly deposited, which means a mated female may sometimes present with no sphragis, or a mated male may present with a sphragis retained in his claspers.[3]
Flight Patterns
The flight period of the Parnassius smintheus spans the first week of June in low elevations to late September in alpine tundra. The species is univoltine.[3] Male butterflies tend to be more apparent than females. Females of this species generally avoid flying, preferring to search for oviposition sites by crawling, whereas males more readily take flight. However, dispersal distances have been found to be similar for the two sexes. Most movement occurs through non-forested areas and little movement occurs across valleys.[4] Typically, the greatest number of flights occur 20 meters into meadows while the fewest occur 20 meters into forests, and the mean flight distances were higher in the meadows than in the forests. The readiness of the Parnassius smintheus to fly is correlated with light intensity, as it was observed that the number of flights increased as light intensity increased.[12]
Conservation
Parnassius smintheus butterflies are currently abundant in the Rocky Mountains, but closely related species Parnassius apollo and Parnassius mnemosyne are threatened in Europe due to habitat loss and population isolation. These phenomena are beginning to occur for the Parnassius smintheus as well. Due to fire suppression and possibly global warming, the tree line has risen while the meadow areas have decreased by over 78% since 1952. Conservation efforts would best be directed at conserving remaining habitat and promoting connectivity among existing populations.[6] Connectivity may be maintained by preventing forest encroachment and maintaining unforested corridors among patches.[4]
External links
- Funet Taxonomy, distribution, images
- Butterflies of America images including types and habitats
- P. smintheus images at Consortium for the Barcode of Life
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References
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