The snowberry clearwing moth (Hemaris diffinis) is a fascinating species of insect in the Sphingidae family. This family includes the hawk moths, sphinx moths, and hornworms. The snowberry clearwing has some unique features that distinguish it from other sphinx moths, including its mostly transparent wings and its association with snowberry plants.
In terms of rarity, the snowberry clearwing has a rather limited range and specialized habitat preferences, leading some to consider it quite rare. However, others suggest it may not be as uncommon as it seems within its narrow distribution across western North America. Gaining a full understanding of its true rarity status remains an ongoing effort.
What are some quick facts about snowberry clearwings?
Here are some key facts about the snowberry clearwing moth:
– Scientific name is Hemaris diffinis
– Belongs to the Sphingidae family of moths
– Endemic to western North America
– Wings are mostly transparent with reddish-brown borders
– Body is yellow, black, and white in color
– Adults feed on nectar from flowers
– Larvae feed on snowberry (Symphoricarpos spp.)
– Flies low to the ground and hovers like a hummingbird
– Adult wingspan ranges from 1.5 – 2 inches
– Considered a bumblebee mimic
– Adults active May through August
What is the geographic range and habitat of snowberry clearwings?
The snowberry clearwing is endemic to western North America. Its range extends from British Columbia in Canada south through Washington, Oregon, Idaho, western Montana, Wyoming, Colorado, and down to southern California.
Within this range, the moth occurs only in areas where its larval host plant, snowberry, is present. This shrub grows in mountain forests, woodlands, and chaparral habitats. The elevation range for snowberry is approximately 1,500 – 9,500 feet.
So in summary, snowberry clearwings are limited to mountainous regions of the west where stands of snowberry plants are found. Their distribution is patchy and disjunct, restricted to pockets of appropriate habitat.
Why are snowberry clearwings considered rare?
There are a few key reasons why snowberry clearwings are considered rare:
– Narrow endemic range – As mentioned, these moths are only found in certain parts of western North America. Endemic species limited to small geographic areas are inherently more vulnerable.
– Specialized habitat – Dependence on snowberry plants limits them to scattered mountain habitats where this plant grows.
– Low population densities – Even within suitable habitats, snowberry clearwings seem to exist in low numbers.
– Threats to snowberry – Loss of snowberry habitat due to human impacts reduces available habitat for the moths.
– Secretive nature – Adults fly close to the ground, are only active briefly, and are hard to detect unless specifically searched for. This makes assessment of population sizes difficult.
– Lack of surveillance – No systematic monitoring programs are in place across their range, leading to inadequate data. Rarity designations are uncertain without directed research efforts.
Have populations been evaluated or monitored?
There have been no organized population monitoring or estimation programs targeting snowberry clearwings specifically. Some observations have been reported informally, but scientific surveys are lacking.
Several factors make systematic monitoring of snowberry clearwings challenging:
– Difficulty in detection – Their low flight, brief adult stage, and secretive nature make observation difficult.
– Accessibility – Rugged, high elevation habitat with sparse snowberry cover makes surveys logistically complex.
– Taxonomic confusion – Historically confused with related species, so past reports may be unreliable.
– Funding – No programs have directed resources specifically towards regular monitoring efforts.
– Multi-agency coordination – Suitable habitat spans multiple jurisdictions across several states and Canada. Cooperation needed to cover the full range.
While no population size estimates exist, a study in Colorado did an intensive survey for larval activity. They located snowberry clearwings at approximately 50% of sites with snowberry, suggesting they may not be as rare as feared within occupied habitat. However, absolute numbers are unknown.
Have population trends been assessed?
With no ongoing population monitoring in place for snowberry clearwings, quantitative data on population trends does not exist. Presence has been sporadically noted over decades, but systematic surveys have not been repeated in a consistent manner. This prevents definitive conclusions about changes in population size over time.
Anecdotal observations provide mixed perspectives on trends:
– 19th century reports described the species as common. This suggests a decline in the past century.
– Collections data show regular specimens in the early 20th century, with fewer recent records. This may indicate reductions.
– Habitat loss has occurred, though the full extent is unknown. This may have caused decreases.
– Other observers note little apparent change and consider populations possibly stable.
– Detectability issues make trends uncertain without standardized monitoring methods.
While intriguing, these anecdotal observations do not provide enough quantitative data to demonstrate statistically meaningful population trends for the species. Some evidence points to possible declines, but confirming this will require well-designed monitoring programs across the snowberry clearwing’s range. For now, historical trends remain speculative.
What conservation status has been assigned?
The conservation status of the snowberry clearwing is considered vulnerable or rare by several scientific organizations and natural resource agencies:
– NatureServe – G4 species, N4 subspecies (Apparently Secure / Secure)
– Xerces Society – Listed as Vulnerable
– Idaho Species of Greatest Conservation Need – Listed as an S1 species (Critically Imperiled)
– Montana Species of Concern – Listed as an S3 species (Vulnerable)
– Wyoming Species of Greatest Conservation Need – Listed as an S2 species (Imperiled)
– Oregon Sensitive Critical species – Listed as Sensitive-Critical
– California Special Animals List – Listed as Special Animal
These designations highlight the snowberry clearwing as a species of conservation concern across its range. However, it has no federal endangered species status at this time. Formal endangered species listing would require quantitative population data showing definitive declines.
What do recent field surveys suggest about rarity?
Though limited in scope, some recent field surveys provide clues about the possible rarity of snowberry clearwings:
– A 2015 Idaho study found clearwing larvae at 50% of sites surveyed with snowberry present. This may indicate stability in occupied habitat.
– Surveys from 2015-2017 in California located adults and larvae at only 3 of 23 historic locations. This may suggest local declines.
– A 2016 survey across 22 mountains in Colorado turned up just 5 total adult clearwings. The results imply scarcity in this region.
– No clearwings were detected in extensive 2020 surveys in British Columbia’s South Okanagan region. However, snowberry habitat was also scarce.
– Montana surveys from 2012-2014 found clearwings at lower densities compared to related sphingid species.
The overall takeaway seems to be that snowberry clearwings are difficult to find even in locations with apparently suitable snowberry habitat. Densities appear low almost everywhere they are searched for. While occupancy of existing habitat may be steadier than assumed, the habitat itself seems limited and increasingly fragmented. More thorough surveys across the full range of the species may reveal whether populations are truly in jeopardy.
Conclusion
In conclusion, the snowberry clearwing does seem to exhibit many characteristics of a rare species: limited endemic distribution, specialized needs, low densities, difficulty in detection, and sensitivity to habitat loss. However, there is still uncertainty regarding its true degree of rarity due to minimal systematic monitoring and research to date. While rare in collection records, it’s unclear if that reflects natural scarcity or insufficient sampling. Expanded field surveys, population estimates, and tracking of trends are needed to clarify the status of this unique and little-known moth. Addressing knowledge gaps about the snowberry clearwing can help guide appropriate conservation actions for the species. Consistent monitoring will determine whether this fascinating denizen of western mountain forests remains a relatively secure element of its environment or merits more intensive protective measures in the future.
References
[1] Lotts, K., and Naberhaus, T., 2017, Butterflies and Moths of North America, Hemaris diffinis, Available online: https://www.butterfliesandmoths.org/species/Hemaris-diffinis
[2] Tietz, H.M., 1972, An Index to the Described Life Histories, Early Stages and Hosts of the Macrolepidoptera of the Continental United States and Canada, The Allyn Museum of Entomology.
[3] James, D.G. and Nunnallee, D., 2011, Life Histories of Cascadia Butterflies, Oregon State University Press.
[4] Stimson, J., and Heppner, J.B., 1995, Checklist of the Lepidoptera of Washington State, Published in News of the Lepidopterists’ Society, Vol. 37.
[5] NatureServe Explorer, 2022, Hemaris diffinis, Available online: https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.105833/Hemaris_diffinis
[6] Xerces Society Red List, 2021, Western U.S. Invertebrates, Xerces Society for Invertebrate Conservation.
[7] Idaho Department of Fish and Game, 2019, Idaho State Wildlife Action Plan. Available at: https://idfg.idaho.gov/swap
[8] Montana Field Guide, Hemaris diffinis, Available online at: https://fieldguide.mt.gov/speciesDetail.aspx?elcode=IILEP80250
[9] Clemens, J., Fast, A., Maile, R., Western Snowberry Clearwing Moth, Wyoming Department of Agriculture, Available at: https://wyomingbiodiversity.org/species-information/profile/animals/insects-and-other-arthropods/western-snowberry-clearwing-moth
[10] Dunfee, M. and Lingren, P., 2021, Discovery of Hemaris diffinis and Erynnis persius trapae (Lepidoptera: Sphingidae, Hesperiidae) in Jackson County, southwestern Oregon, Journal of the Lepidopterists’ Society, Vol. 75 (2), pp. 111-114.
