Research Article |
Corresponding author: B. Christian Schmidt ( christian.schmidt@canada.ca ) Academic editor: Thomas Simonsen
© 2016 B. Christian Schmidt, Ross A. Layberry.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Schmidt BC, Layberry RA (2016) What Azure blues occur in Canada? A re-assessment of Celastrina Tutt species (Lepidoptera, Lycaenidae). ZooKeys 584: 135-164. https://doi.org/10.3897/zookeys.584.7882
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The identity of Celastrina species in eastern Canada is reviewed based on larval host plants, phenology, adult phenotypes, mtDNA barcodes and re-assessment of published data. The status of the Cherry Gall Azure (C. serotina Pavulaan & Wright) as a distinct species in Canada is not supported by any dataset, and is removed from the Canadian fauna. Previous records of this taxon are re-identified as C. lucia (Kirby) and C. neglecta (Edwards). Evidence is presented that both Celastrina lucia and Celastrina neglecta have a second, summer-flying generation in parts of Canada. The summer generation of C. lucia has previously been misidentified as C. neglecta, which differs in phenology, adult phenotype and larval hosts from summer C. lucia. DNA barcodes are highly conserved among at least three North American Celastrina species, and provide no taxonomic information. Celastrina neglecta has a Canadian distribution restricted to southern Ontario, Manitoba, Saskatchewan and easternmost Alberta. The discovery of museum specimens of Celastrina ladon (Cramer) from southernmost Ontario represents a new species for the Canadian butterfly fauna, which is in need of conservation status assessment.
Voltinism, Cornus , Viburnum , Eastern Flowering Dogwood, Eriophyidae , Cherry gall, degree-day model, DNA barcode
Blues of the genus Celastrina Tutt, commonly known as azures, are perhaps the most familiar spring butterflies in Canada, occurring in all ecoregions except the high arctic. Despite their ubiquity, their identification and taxonomy is difficult, with species boundaries and nomenclature having a long history of controversy and confusion. Forty years ago, all North American Celastrina taxa were generally considered to represent variation within a single species described from Europe, C. argiolus (L.) (
The conservative morphological variation between most Celastrina species, coupled with adult seasonal polyphenism, has been a major impediment to Celastrina taxonomy and dictated a gradual refinement of species concepts. Comparative data on molecular variation, physiology, development and ecology for sympatric or closely parapatric populations are therefore particularly important in evaluating species concepts, yet such data are largely lacking (but see
Four Celastrina species are currently attributed to the Canadian fauna, three of them found in the East. The fourth species, C. echo (Edwards), is strictly western and although previously ranked as a subspecies of C. ladon (Cramer) (e.g.
Current concept (Pelham 2011) |
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Scott 1984 |
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C. lucia | lucia (+ lucia auct.) | C. ladon | C. ladon lucia | C. ladon lucia | C. ladon lucia | C. argiolus |
C. serotina | C. serotina | C. ladon | C. l. ladon | C. sp. n. | C. ladon “violacea II” | C. argiolus |
C. neglecta | C. neglecta | C ladonneglecta | C. neglecta | C. neglecta | C. ladon neglecta | C. argiolus |
C. echo | n/a | C. ladon | n/a | C. ladon nigrescens, C. ladon echo | C. ladon nigrescens, C. ladon echo | C. argiolus |
C. ladon | C. ladon | C. ladon | C. ladon ladon | n/a | C. ladon “violacea I” | C. argiolus |
Celastrina lucia, the Northern Azure (a.k.a. Spring Azure, a name here reserved for C. ladon), is the most widespread azure, occurring in every province and territory. In the boreal and subarctic regions it is the only species of the genus. The Northern Azure has been considered to be univoltine throughout its range, flying in early spring (
Celastrina neglecta, the Summer Azure, has a more southerly but overlapping distribution with C. lucia and is recorded from all provinces except British Columbia, Newfoundland and Labrador. It is distinguished from C. lucia by its later flight season, in Canada flying mostly in July, six to eight weeks after the peak flight of spring-flying C. lucia. All summer-flying Celastrina in southern Canada have been assigned to C. neglecta (
Celastrina serotina, the Cherry Gall Azure, is also a univoltine species but with a late spring flight, between that of C. lucia and C. neglecta. There is some doubt in the species status of Ontario populations of C. serotina, as larvae reared from cherry galls in the spring can produce C. neglecta-type adults in the same season (
Celastrina ladon, the Spring Azure, has not been reported in Canada in the sense of the modern concept of the species, where the diagnostic male wing scale morphology (Fig.
Specimens examined during this study included those deposited in the Canadian National Collection of Insects, Arachnids and Nematodes (
Molecular variation of Celastrina species was assessed using the COI barcode fragment, with DNA extraction, PCR amplification, and sequencing performed at the Canadian Centre for DNA Barcoding (CCDB), following standard protocols (
DNA sequences were analyzed on the Barcode of Life Data Systems website (BOLD, www.boldsystems.org). The dataset was filtered to include only records with sequences greater than 600 base-pairs in length, and with voucher specimen photographs and collection data that made independent species identification possible. Sequence variation was analyzed using the Kimura-2-Parameter (K2P) distance model and the neighbor-joining (NJ) algorithm as implemented on BOLD. Voucher specimen data is given in Suppl. material
Larvae were collected from the wild to compare phenology and voltinism of C. lucia and C. serotina, and to obtain comparative study specimens unambiguously associated with the current concept of C. serotina. Celastrina serotina is univoltine with a peak flight after that of C. lucia (
site # | Locality | Lat | Long |
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1 | CAN: ON, Ottawa, Stony Swamp Conservation Area, Richmond Rd. | 45.29 | -75.83 |
2 | CAN: ON, Ottawa, Stony Swamp Conservation Area, Timm Dr. | 45.315 | -75.86 |
3 | CAN: ON, Ottawa, Stony Swamp Conservation Area, Cassidy Rd. | 45.323 | -75.806 |
4 | CAN: ON, Ottawa, Stony Swamp Conservation Area, Watts Ck. | 45.341 | -75.869 |
5 | CAN: ON, Ottawa-Carleton Dist., Carp Hills | 45.386 | -76.075 |
6 | CAN: ON, Hastings Co., Madoc, 3km W | 44.5 | -77.51 |
7 | CAN: ON, Lanark Co., Pakenham, 4 km W, 9th Concession Rd. | 45.304 | -76.331 |
8 | CAN: ON, Lanark Co., Pakenham, 12 km SW, Bellamy Rd. | 45.276 | -76.418 |
As a proxy for mean seasonal abundances of Celastrina taxa, observation records spanning from 1895-2014 were compiled from the Ontario Butterfly Atlas (
Assessing flight peaks based on phenological data combined for multiple taxa could underestimate the number of taxa, if relative abundance discrepancies are large and flights overlap. Emergence patterns were therefore independently assessed through field surveys of eggs, larvae and adults 1–2 × per week in 2015. These data were supplemented with Celastrina records and accompanying voucher photographs available on
To assess between-region differences in adult emergence times due to climatic differences, phenology data were examined using a simple degree-day model (e.g.
DDLTT = [((Tmax - Tmin) / 2)–LTT]
where DD = degree-days, Tmax and Tmin = daily maximum and minimum temperatures, respectively, and LTT = the lower threshold temperature of insect development. LTT is the temperature at which physiological development is negligible, for the species and life stage under study. LTT values of 6 °C to 10 °C are generally implemented for insects, with values in the lower range corresponding to temperate-zone species (e.g.
Examination of forewing scale structure in male Celastrina specimens from southern and eastern Ontario led to the discovery of four specimens of C. ladon: ON, [Norfolk Co.], Normandale, 22.May.1956, J.R. Lonsway; ON, [Norfolk Co.], St. Williams, 7.May.1977, J.T. Troubridge; ON, Elgin Co., Calton Swamp WMA, 7.May.2000, I. Carmichael. Two female specimens are likely also C. ladon, one from Normandale, 28.May.1956, J.R. Lonsway, and one from St. Williams with the same date and collector as the male. All are from the Carolinian forest region of Lake Erie (Fig.
DNA barcode data were available for three North American Celastrina species (C. echo, C. neglecta, and C. lucia, based on independent identification), and representative Eurasian C. argiolus from seven countries (Fig.
Neighbour-joining tree of DNA barcode sequences for Celastrina, with specimen voucher number and country of origin at branch tips. North American samples include 79 samples represented by four haplotypes, with h03 shared among three species (n=76) and remaining three haplotypes with one sample each of C. lucia (h01) and C. neglecta (h02, h04). Voucher data is given in Suppl. material
Nearly all samples of C. lucia, C. neglecta and C. echo shared an identical DNA barcode. A single haplotype (h03, Fig.
Eggs and larvae of C. lucia were found on flower buds and inflorescences of nine species of shrubs in eastern Ontario (Table
Flowering phenology of deciduous shrubs and larval hosts of C. lucia in the Ottawa region.
Phenology | Host1 | Shrub species | Family | Source2 | Site # |
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very early spring | N | Prunus nigra | Rosaceae | a | 2 |
N | Prunus pennsylvanica | Rosaceae | a | 1,2,5 | |
N | Amelanchier spp. | Rosaceae | a | 1,2,4,5,8 | |
N | Vaccinium sp. | Ericaceae | a | 1,5 | |
early spring | Y | Prunus serotina | Rosaceae | a,b | 1,2 |
Y | Prunus virginiana | Rosaceae | a,b | 1,2,8 | |
(Y) | Cornus sericea | Cornaceae | c | - | |
mid to late spring | Y | Cornus alternifolia | Cornaceae | a,b | 1,3,4 |
Y | Cornus rugosa | Cornaceae | a | 5 | |
Y | Viburnum cassinoides | Caprifoliaceae | a | 1,3,4 | |
Y | Viburnum lentago | Caprifoliaceae | a | 1,3,4 | |
(Y) | Viburnum rafinesquianum | Caprifoliaceae | a | 6,7 | |
(Y) | Diervilla lonicera | Caprifoliaceae | a | 5 | |
(Y) | Celastrus scandens | Celastraceae | a | 6 | |
mid summer | Y | Spiraea alba | Rosaceae | b | - |
(2nd generation) | N | Spiraea latifolia | Rosaceae | b | - |
Other deciduous shrubs flowering during and after the spring flight season of Celastrina were sampled opportunistically, but failed to yield larvae, even when larvae were common on other shrub species at the same sites. These included Ilex verticillata (L.) A. Gray, Ilex mucronata (L.) (both Aquifoliaceae), and Lonicera tatarica L. (an introduced invasive shrub), Cornus racemosa Lam., Vaccinium angustifolium Ait., and Gaylussacia baccata (Wangenh.) K. Koch. An extensive search of the introduced Viburnum lantana L. at one site (#2) yielded one half-grown larva, which died several days later in captivity feeding on this plant. Ilex is the sole host of Celastrina idella Wright and Pavulaan, but is thought to be toxic to C. lucia (Wright and Pavulaan 2005). Cornus sericea L. is a common host of boreal C. lucia populations, but searches for larvae in the study area (site #1) were unsuccessful, despite the patchy but common occurrence of this shrub. Virtually all of the host plants recorded above have completed flowering prior to the onset of summer C. lucia flights, which strongly favor Spiraea alba Du Roi as oviposition sites and larval hosts (Table
Most of the C. lucia host shrubs present in the eastern deciduous forest are absent in the boreal region further north. Within the host genera Cornus and Viburnum, C. sericea and V. edule (Michx.) Raf. occur widely in the boreal region, but only sporadically in certain plant communities. By contrast, species of Ericaceae are ubiquitous and constitute the main larval hosts in many parts of the ecoregion, particularly plant communities on acidic substrates such as granite barrens, sand plains and bogs. Host plants documented along the James Bay highway in northern Québec in June 2015 (BCS, unpubl. data) included Cornus sericea, Rhododendron groenlandicum (Oeder) Kron & Judd and Kalmia polifolia Wangenh. Searches on V. edule and Prunus pensylvanica failed to yield eggs or larvae.
Larvae found on different plant genera exhibited different colour morph frequencies. Larvae on Cornus alternifolia were mostly very pale, pastel-green with little patterning (Fig.
Of approximately 120 gall-feeding larvae found on 18 Prunus serotina trees heavily infested with eriophyid galls, 28 were retained for rearing. Based on size and duration to pupation, approximately 75% were penultimate or ultimate instar, but younger instars were present also. A similar age distribution was observed among Celastrina larvae on other hosts at the same time and location, based on collection of 30 larvae from Viburnum lentago and Cornus alternifolia. Twenty-two of 28 larvae from galls survived to pupation, with five adults emerging between June 29th and July 2nd (summer phenotype) and three more emerging within 9 days at room temperature (spring phenotype) after a 95-day treatment of winter diapause conditions at 5 °C in a conventional refrigerator. The remaining 14 pupae failed to merge and were dissected, revealing fully developed but desiccated adults, which could be assigned to either summer or spring phenotype by comparison to pinned specimens (Fig.
Similar results were obtained from rearing of cherry-gall feeding larvae collected in June of 2004 (RAL), where some pupae yielded summer-phenotype adults in the same year, and some entered diapause to emerge as spring-phenotype adults the following year (Suppl. material
Phenology of cherry gall-feeding larvae was not notably different from that of larvae on other hosts, contrary to the prediction that larvae should appear later based on a later flight period in late May to late June, after that of C. lucia (
Stage | Duration (days) | Temp. (deg. C) | Source region | Data source | |||
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min | max | avg | n | ||||
egg | 3 | 6 | 4.5 | - | 19–22 | Washington |
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Larva | 12 | 22 | 16.4 | 5 | 21 | Ontario | This study |
16 | 25 | 20.5 | - | 18–27 | Washington |
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Pupa | 11 | 14 | 12.7 | 7 | 21 | Ontario |
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8 | 19 | 13 | 5 | 21 | Ontario | This study | |
7 | 13 | 10 | - | 18–27 | Washington |
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7 | - | - | - | 22 | Michigan |
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The alternative taxonomic explanation is that gall-feeding larvae are C. lucia, utilizing an unusual plant resource that is, however, similar to a Prunus flower bud in size, shape, tissue consistency, and likely phytochemistry. With a relatively long spring flight period and short flowering phenology for a given host species, C. lucia must use a suite of hosts to match larval development to host phenology. Galls extend the temporal availability of Prunus as they are present longer than flower buds. The total flight season for C. lucia is over a month in a given year (Table
Comparing degree-day accumulation to flight abundances provides a standardized comparison of flight seasons between southern and eastern Ontario (as defined here), where different climatic conditions prevail. In other words, peak adult emergence is expected to have similar degree-day (DD6) accumulation values (dictated by physiological developmental constraints) in regions with differing climates, even though flight times could have quite different calendar dates. Furthermore, DD6 accumulation can be used to assess if climatic conditions are amenable to producing multiple yearly generations (multivoltinism).
Cumulative DD6 during the spring and summer months was greater for southern compared to eastern Ontario (Table
Comparison of accumulated degree-days (DD6) on selected dates for Ottawa and London, Ontario, based on daily temperatures averaged for 2009–2015. Time lag represents the number of days that London is ahead of Ottawa, based on DD6 values averaged for the preceding week.
Date | Ottawa | London | Time lag (d) |
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01-Apr | 0.0 | 0.0 | 0.0 |
10-Apr | 0.7 | 3.4 | 5.5 |
20-Apr | 10.5 | 21.5 | 5.5 |
30-Apr | 35.2 | 51.4 | 4.3 |
10-May | 105.3 | 123.4 | 2.5 |
20-May | 179.8 | 200.5 | 2.5 |
30-May | 288.2 | 314.4 | 2.1 |
10-Jun | 403.0 | 431.2 | 2.5 |
20-Jun | 528.0 | 562.6 | 2.5 |
30-Jun | 675.7 | 707.0 | 2.2 |
10-Jul | 830.5 | 854.7 | 1.6 |
20-Jul | 987.1 | 1011.5 | 1.5 |
30-Jul | 1132.8 | 1158.3 | 1.8 |
Date | adults1 | eggs | larvae | pupae | Note |
Apr 19 | X | | | | | | | First-of-year (FOY) record for adults; only males present |
Apr 28 | X | | | | | | | adults common, FOY females |
May 6 | X | x | | | | | adults common, female oviposition behaviour observed |
May 12 | X | X | X | | | Hatched and unhatched eggs at site #2 |
May 14 | X | X | X | | | Adults, eggs, and larvae at site #1 |
May 21 | x | X | X | Eggs and larvae present but no adults (site #5) | |
May 26 | X | x | X | | | Adults and mature larvae (site #1) |
May 28 | x | x | X | | | Mature larvae (site #1) |
May 29 | X | x | x | | | End of flight period, only 3 worn adults seen in 3h |
Jun 2 | X | x | X | | | One worn adult |
Jun 4 | X | x | X | | | One worn adult |
Jun 9 | | | | | x | x | FOY pupae predicted2 |
Jun 11 | | | | | X | x | Larvae (site #3,4) |
Jun 14 | | | | | X | x | Larvae (site #3) |
Jun 18 | | | | | X | x | Larvae (site #3) |
Jun 20 | X | | | | | x | FOY summer brood adults - male |
Is it possible that summer abundance peaks represent the offspring of spring Celastrina? Currently, spring and summer Celastrina are treated as separate species, and some have maintained that Celastrina flying subsequent to the spring flight appear too soon for this to be possible (e.g.
Average life cycle duration of non-diapausing Celastrina in Ontario (35d total; egg = 5d, larva = 17d, pupa = 13d at 22 °C; Table
Celastrina phenology in eastern Ontario exhibits a bimodal pattern, with a well-defined spring and summer peak. Median spring abundance (i.e., 50% of records) occurs on May 8th and median summer abundance on July 12th (spring and summer periods divided by the trough midpoint at June 21st). Celastrina abundance drops sharply between June 5th and June 24th; in other words, azures of any kind are very rarely observed in eastern Ontario during this period (Fig.
Another notable difference in Celastrina phenology between eastern versus southern Ontario is the magnitude of spring (April–May) versus summer (July onwards) abundance peaks. In southern Ontario, there are considerably fewer spring than summer records, the converse of the pattern in eastern Ontario. Celastrina abundance also persists further into the summer in southern Ontario, not declining significantly until after Aug 21st, compared to steady declines after mid-July in eastern Ontario (Fig.
The bimodal abundance pattern in eastern Ontario reflects at minimum two entities, a spring- and a summer-flying Celastrina, previously considered to be C. lucia and C. neglecta, respectively. The time lag between spring and summer emergences, and the rearing results and phenotype comparisons discussed below, indicate that eastern Ontario spring and summer Celastrina represent two broods of the same species, C. lucia.
Although there is no evidence of a third peak (in eastern Ontario) intercalated between the first and second as would be expected for C. serotina, it is possible that such an abundance signature is hidden by virtue of C. serotina being much rarer than C. lucia and C. neglecta. However, the 2015 observations on larval and adult phenology do not support this (Table
Hypothetical phenology of Celastrina species in southern Ontario. Celastrina lucia abundance is based on eastern Ontario data (Figure
In southern Ontario, spring Celastrina are rare compared to the abundance of azures seen from June onwards (
Adult males of Celastrina. a–c Celastrina ladon (Cramer) a Normandale, ON, CAN, 22 May 1956, J.R. Lonsway, (CNCLEP 116459) b St Williams, ON, CAN, 7 May 1977, J.T. Troubridge (CNCLEP 116460) c St Louis, Missouri, United States, 15 April 1979 (CNCLEP 116461) d–f Celastrina lucia (Kirby), spring generation d, e, f Stony Swamp, Richmond Road, Ottawa-Carleton, ON, 45.298°N, 75.828°W, CAN, 28 April 2015, B.C. Schmidt (CNCLEP 116445, 116447, 116446) g–k Celastrina lucia (Kirby), summer generation g Riding Mtns., MB, 12 June 1938, J. H. McDunnough (CNCLEP 116448) h Timm Dr., Ottawa, ON, 45.315°N, 75.860°W, CAN, 14 May 2015, B.C. Schmidt (CNCLEP 116451) i Bobcaygeon, ON, CAN, 16 July, 1932, J. McDunnough (CNCLEP 116453) j Pont Neuf, QC, CAN, 8 July 1973, no collector (CNCLEP 116454) k Britannia, Ottawa, ON, CAN, 30 June 1949, R. deRuette (CNCLEP 116455) l–o Celastrina neglecta (Kirby) l Larsson’s Camp, One Sided Lake, ON, CAN, 19 June 1960, M.R. MacKay (CNCLEP 116464) m Point Erie, ON, CAN, 6 August 1950, T.N. Freeman (CNCLEP 116465). Riding Mountains, MB, CAN, 13 June 1938, J. McDunnough (CNCLEP 116466) o Riding Mountains, MB, CAN, 12 June 1938, J. McDunnough (CNCLEP 116467).
The spring/summer abundance discrepancy in southern Ontario was also noted by
The complex abundance peaks for southern Ontario are at least in part a result of combined data for multiple species. Degree-day modelling can however be used to approximate the apparent abundance peaks. Given a spring peak of C. lucia on May 8, and an average DD6 accumulation of 750 to reach the second-brood peak (based on the eastern Ontario phenology), summer C. lucia would be expected to peak on July 11th on average. A corresponding, although weak, peak occurs in southern Ontario between July 5th and 14th (Fig.
To establish comparative phenotypes of C. neglecta and summer-brood C. lucia, southern Ontario specimens collected during the June flight peak (Figure
In Canada, C. neglecta is sympatric with C. lucia in nearly all parts of the neglecta range. Most summer records from the Prairie Provinces proved to be C. neglecta (Fig.
The Canadian Celastrina fauna is revised to consist of four species: C. lucia (all provinces and territories), Celastrina neglecta (southern Ontario to eastern Alberta), C. ladon (Carolinian zone of southernmost Ontario), and C. echo (southern British Columbia and southwestern Alberta). From eastern Ontario eastward, what was previously treated as three Celastrina species is revised to a single, facultative bivoltine species, C. lucia. Adults of C. lucia flying from early to mid-spring, in a relatively prolonged emergence, give rise to a second and possibly a partial third generation in July to September. Larval rearing, phenology, and seasonal emergence patterns show no evidence of C. serotina as a separate gall-feeding species distinct from C. lucia, and C. serotina is therefore removed from the Canadian fauna. Whether or not nominate C. serotina (described from Rhode Island) is a valid species, or simply represents late-emerging C. lucia that utilize cherry galls, needs to be re-evaluated. Molecular markers such as microsatellites could prove to be particularly valuable in advancing the taxonomy of Celastrina, given that the COI barcode marker is taxonomically uninformative here.
Two additional possibilities in the identity of the species here assigned to C. lucia warrant comment. It is conceivable that C. neglecta is present as a univoltine, summer-flying entity that is phenotypically similar to and unrecognized within summer-brood C. lucia. This would require that the June-flying Celastrina in southern Ontario be C. serotina, and that Celastrina neglecta in eastern Ontario overwintering as pupae delay emergence until July. Both of these conditions are improbable; the identity of June Celastrina in southern Ontario is most likely C. neglecta as discussed below, and there are no known temperate-zone Lycaenidae that overwinter as pupae and delay emergence until July. Eastern Ontario summer Celastrina also have the appearance of pale C. lucia (Figs
Adult females of Celastrina. a–b Celastrina ladon (Cramer) a Normandale, ON, CAN, 28 May 1956, J.R. Lonsway (CNCLEP 116462) b Lake Wellington, Washington Co, Arkansas, United States, 12 April 1974 no collector (CNCLEP 116463) c–e Celastrina lucia (Kirby), spring generation c Stony Swamp, Richmond Road, Ottawa-Carleton, ON, 45.298°N, 75.828°W, CAN, 28 April 2015, B.C. Schmidt (CNCLEP 116449) d Bells Corners, Timm Road, Ottawa, ON, 45.315°N, 75.860°W, CAN, 14 May 2015, B.C. Schmidt (CNCLEP 116450). e) Timm Dr., Ottawa, ON, 45.315°N, 75.860°W, CAN, 14 May 2015, B.C. Schmidt (CNCLEP 116451) f–g Celastrina lucia (Kirby), summer generation f Château-d’Eau, QC, CAN, 21 July 1990, J.-P. Laplante (CNCLEP 116456) g Celastrina lucia (Kirby): 5kmSE of Fitzroy Harbour, Fitzroy, ON, 45.4348°N, 76.1725°W, CAN, em 20 June 2015, Ross Layberry (CNCLEP 116457) h Stony Swamp, Richmond Road, Ottawa-Carleton, ON, 45.297°N, 75.836°W, CAN, 2 July 2015, B.C. Schmidt (CNCLEP 116458) i–k Celastrina neglecta (Kirby) i Harrow, Essex Co., ON, 42.0390°N, 82.9080°W, 28 May 2015, Jeff Larson (CNCLEP 116468) j Simcoe, ON, CAN, 26 June 1939, T.N. Freeman (CNCLEP 116469) k Bobcaygeon, ON, CAN, 22 June 1932, J. McDunnough (CNCLEP 116470).
The second possibility is that the eastern Ontario taxon represents a species distinct from nominate C. lucia, that is C. lucia ‘of authors’ in the sense of
Although consistently stated to be univoltine in the literature, Celastrina lucia is here interpreted to be facultatively bivoltine (and possibly trivoltine) in southern Canada (Fig.
Rearing data indicate that a proportion of spring individuals of Ontario C. lucia enter diapause the following spring (
Larvae of C. lucia are polyphagous, but show preferences for several genera in different families (Table
In southern Ontario, a third Celastrina species appears in late spring after an initial May flight of both C. lucia and C. ladon. The appearance of this species is too soon after the first flight of Celastrina to represent a second annual generation. Adult wing phenotype is similar to the summer brood of C. lucia, but differs in having darker, smaller and more sharply defined ventral spots, more reduced marginal markings, a solid white dorsal hindwing fringe, and a less evenly checkered forewing fringe (Table
Species | Maximum annual # generations | Peak flight times | Distribution | Male forewing androconial scales | Male forewing overlapping scales | Ventral hindwing: confluent discal macules | Ventral Hindwing: confluent marginal markings | Ventral hindwing: expression and colour of marginal markings | Ventral ground colour | Hindwing fringe | Dorsal hindwing | Dorsal forewing |
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C. lucia | 3? | E - L May; E - L Jul | Ubiquitous through most of province; localized south of 43N | present | absent | common | common | spring: well-developed, diffuse, brown to grey. Summer: moderately developed, usually light brown-grey | Spring - grey to greyish white; rarely white. Summer - white | white with black fringe at vein termini | summer: extensive white scasling; ventral pattern usually visible | Fringe and terminal area evenly checkered from apex to tornus, or slightly darker at apex |
C. neglecta | 2? | L May - L June; L Jul - L Aug | Primarily south of 44.5N, but northern limits uncertain | present | absent | rare | rare | poorly developed, small and dark grey; marginal crescents often absent | white | solid white | limited or sparse white scaling; ventral pattern not usually visible | Fringe and terminal area darker in apical area, with termina lblack line usually widest at apex |
C. ladon | 1 | L Apr - M May | Carolinian zone south of 43N | absent | present | rare | rare | moderately developed, diffuse, brown to grey | grey to greyish white | white with black fringe at vein termini | limited or no white scaling | Margin evenly checkered from apex to tornus, or slightly darker at apex |
In Ontario, this taxon was recognized as distinct from C. lucia 140 years ago by
Canadian host plant records that are probably attributable to C. neglecta include Ceanothus americanus (based on late June larvae from Northumberland Co., Ontario;
The Spring Azure, C. ladon, is here confirmed as part of the Canadian fauna. It is currently known from only three sites, with the most recent record from 2000. Surveys for this species are urgently needed as the primary larval host, Eastern Flowering Dogwood (Cornus florida L.), is endangered in Canada (
Surprisingly, there are still many large gaps in our understanding of Celastrina taxonomy and biology. The most urgent need for Canadian Celastrina research is vouchered surveys for C. ladon in southern Ontario, so that potential conservation needs can be established. Regions where C. neglecta, C. lucia and/or C. ladon occur in sympatry provide an excellent opportunity for comparative study, where time series of vouchers are needed to establish diagnostic as well as habitat and host plant differences. Along similar lines, latitudinal transects of voucher series and host use are needed to examine the transition from southern to boreal C. lucia.
Lastly, controlled-environment rearing studies of all taxa would establish plasticity in voltinism and developmental requirements and diapause triggers. The use of degree-day modeling could easily be fine-tuned as a useful comparative tool for Celastrina taxa and populations, and to model geographic variation of Celastrina emergence. Dearborn and Westwood (2014) used a similar approach to predict emergence of an endangered skipper.
Rick Cavasin kindly made numerous Celastrina photographs available for examination, and provided helpful observations on Celastrina behaviour and variation. Gary G. Anweiler provided data and photographs of Alberta and Saskatchewan Celastrina. Rick Cavasin, Peter Hall, John Klymko, Max Larrivée and Reggie Webster provided feedback and insightful discussion on eastern Celastrina, and Marie-Ève Garon-Labrecque identified eriophyid cherry galls. Alan Macnaughton generously provided additional information on the Ontario Butterfly Atlas database, and Jocelyn Gill provided technical assistance.
Data for DNA barcode voucher specimens of Celastrina
Data type: Microsoft Excel Spreadsheet (.xls)