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The Butterflies of Massachusetts
15 Bronze Copper Lycaena hyllus (Cramer, 1775)
Host Plants and Habitat Relative Abundance Today State Distribution and Locations Broods and Flight Time Outlook
Bronze Copper was described in 1775 by the Dutch naturalist Pieter Cramer, from a female specimen now lost. But the original watercolor drawings of Cramer’s type specimen were recently re-examined by John Calhoun, who deduces from various sources that the specimen was collected by a Thomas James around 1766, probably in Brooklyn, New York, on Long Island--- a habitat which has since been lost to urban sprawl (Calhoun 2010b). Bronze Copper was formerly uncommon to rare in the vicinity of New York City, with many known records, but has not been seen there since 1982 (Glassberg 1993).
Bronze Copper's Massachusetts history is as elusive as the butterfly itself. There is nothing about the Bronze Copper in Thaddeus W. Harris’ writings, and it is not on his list of insects collected around Boston in the 1820's. Thoreau, who walked Bronze Copper’s present-day haunts in the Concord area in the 1850s, does not mention it, although he did comment on the American Copper. Scudder in 1862 terms the species “quite rare” in New England, and it is not on his 1872 list of those “known to occur in Essex County.” He thought it was found mostly to the south and west of New England.
Photo: Erik Nielsen Wayland Community Gardens 8-25-2010
It was, however, known in western Massachusetts, and by 1889 Scudder is able to list records from Amherst (Marsh); Mt. Tom (Morrison); Springfield (“not uncommon” according to Emery and Dimmock); Belchertown (A.C. Sprague); North Leverett (F. S. Sprague); Lenox (“common” according to Edwards); and Williamstown (“rather rare”) (Scudder 1889: 980). Today, the Harvard Museum of Comparative Zoology (MCZ) still has Morrison’s specimen from Mt. Tom (in the Scudder collection, no date); the female from North Leverett taken by F. H. Sprague 8/12/1878; and two specimens from Belchertown taken 8/30/1886 by A. C. Sprague. No other 19th or early 20th century Massachusetts specimens have been located in the MCZ.
So to Scudder’s knowledge at the turn of the century, Bronze Copper had “never been taken east of the Connecticut valley” (1889: 980). This assessment is so at variance with the species’ distribution today that it raises fascinating questions: Did the Bronze Copper migrate eastward only during the 20th century? Could it possibly have been overlooked before 1900 in the well-studied Sudbury River valley, or did it arrive there since then? Is its presence today on Plum Island and other locations in Essex County, and in the Boston area, a fairly recent phenomenon?
The earliest record from east/central Massachusetts -- where Bronze Copper is found in greatest abundance today -- seems to be a specimen from Framingham taken by C. A. Frost, who collected between 1900 and 1916 (cited by Farquhar 1934; specimen location unknown). Thus, Bronze Copper may have expanded eastward shortly after Scudder wrote. After that, the east/central record shows a large time gap; the next reports do not come until 1974, when Willis found Bronze Copper in the Holliston-Framingham area (Lep.Soc.Seas.Sum 1974), and D. Winter collected or bred several specimens from Dover on 6/22/1974, which are now in the MCZ. Winter also collected two specimens from Barre (Worcester Co.) on 7/8/1972, and two males were reported in 1975 from Charlemont (Franklin Co.) by G. Morrell (Lep.Soc.Seas.Sum. 1975).
Interestingly, there are early twentieth-century reports from Essex County in northeastern Massachusetts. In 1924 at Salisbury, near the New Hampshire border, a Bronze Copper was captured September 6 by A. P. Morse of the Peabody Museum in Salem; he believed it to be “the first example recorded from the county.” It was a female in perfect condition found on goldenrod at the edge of the salt marsh. A male was also seen, but not collected. At about the same time, Austin H. Clark (1925: 293-8) reported a specimen from a marshy spot in Essex, caught by his son, Austin B. J. Clark (9/1923 female specimen now at Boston University). In the 1970's, Bronze Copper was collected on Plum Island by Paul Z. Goldstein (8/26/1970 male and female specimens in the MCZ). It still occurs sparingly in Essex County today (see below).
Did Bronze Copper, which has a generally northerly distribution, move south from New Hampshire into Essex County? Or did it migrate northeast along the Sudbury/Concord, and then Merrimack, river valleys? Or perhaps there was always a small coastal population, separate from the west/central populations. Other tantalizing historical questions: did the Bronze Copper die out in the central Connecticut River valley, where it was known in the nineteenth century? It is not found there today. And why has it not been found recently in wet meadows around Lenox in the Berkshires? Map 15 below gives the present-day distribution 1992-2010.
Host Plants and Habitat
Bronze Copper is a wet meadow species, frequenting “the springy margins of brooks” (Scudder 1889). It may well have benefited from pre-industrial agriculture in New England, in areas where light grazing or shifting cultivation kept wet meadows open, encouraging the growth of dock (which cows do not eat) and polygonums (Table 1). But its rarity here historically makes this difficult to demonstrate.
Bronze Copper’s native hosts are (or were) great water dock (Rumex orbiculatus), and swamp or water dock (Rumex verticillatus). In Massachusetts, R. orbiculatus is native to and found in every county of the state except Franklin, and R. verticillatus is native to five counties, though today is quite rare and a threatened species (Sorrie and Somers, 1999; Magee and Ahles 1999). In Ohio, Bronze Coppers have been found and reared on R. orbiculatus (Iftner et al. 1992).
Bronze Coppers are also reported to use native Polygonum amphibium [=coccinium] (Scott 1986) and Polygonum natans (MacLean 1990), Erect and Floating Water Smartweeds, both of which also occur throughout Massachusetts, as do other possible native and non-native hosts among the Polygonaceae (Magee & Ahles 1999; Sorrie and Somers 1999). The older literature is less definite about Polygonum use, but MacLean observed both larvae and pupae on P. natans in Minnesota. In Maine, P. deMaynadier has observed Bronze Coppers ovipositing on Polygonum amphibium in a large riverside sedge meadow in Passadumkeag Twp.; the plant species was confirmed by a botanist (pers. comm. 9/14/2012).
Bronze Copper’s main host today throughout its range is the widespread non-native weed curly dock (Rumex crispus)---another example of a native butterfly adopting a non-native host (See Table 3 "Switchers"). Bronze Coppers have been photographed on curly dock in West Virginia (Allen 1997: Pl. 33), and reared on it in the lab in Connecticut (O’Donnell et al. 2007) and in Massachusetts by M. Rainey, whose photo series at http://www.flickr.com/photos/mcrainey/sets/72157626689740307/ presents all stages of Bronze Copper's life cycle.
Bronze Copper uses curly dock in Wayland, Massachusetts, as documented photographically by M. Rainey (Massachusetts Butterflies 35: 16-17, Fall 2010); in addition, MBC members S. Moore and E. Nielsen have on separate occasions observed ovipositing on curly dock, on the underside of leaves very close to the ground (presumably helping the egg overwinter) in Wayland and Sudbury.
Polygonum may also be a larval host in Massachusetts. Sight reports of ovipositing on polygonum come from Sedge Meadow Conservation Area in Wayland (M. Arey, 9-12-2010), and Wenham Canal, Wenham (A. Grkovich, 8-31-2002), but we still need photographic evidence of ovipositing and larvae. Polygonum amphibium is certainly an important nectar source for Bronze Coppers; photographic evidence by G. Dysart from the Sudbury area can be seen at(http://dysart.zenfolio.com/bronzecoppers/e42a9cf14) (9-12-2012). And there are many reports of Bronze Copper "in association" with Polygonum spp. (probably P. amphibium) (e.g. M. Faherty, Ipswich River WS 9-12-2012). Grass-leaved goldenrod and asters are other favored nectar sources for this butterfly.
As many authors have remarked, it is curious that Bronze Copper is thought to be rare or declining in the eastern United States, given the abundance of both curly dock and polygonums. There may be aspects of its biology and habitat needs which are not well understood, or climate warming might be having an adverse effect.
Relative Abundance Today
Today this species is probably less rare in Massachusetts than in Scudder’s time. The MAS Atlas found Bronze Copper in only 10 of the 723 blocks searched, making it “Rare.” By contrast MBC record totals from the 2000s yield a ranking of Uncommon rather than Rare (Table 5). MBC numbers reflect sustained search efforts and the discovery and informal monitoring of some previously unknown occurrences, for example at Wayland Community Gardens and Wayland Sedge Meadow Conservation Area.
Chart 15: MBC Sightings per Total Trip Reports 1992-2009
No overall population trend should be deduced from Chart 15, because the majority of MBC trips reporting this species were targeted trips, to the specific areas where this species is found, and the effort put in to find the species increased over time. Both Chart 15 and MBC unadjusted totals of individuals seen each year (chart not shown) show a marked increase in Bronze Coppers between 2002 and 2007. This may be mainly a result of the greater effort put in to find this species, and the discovery of new locations. What is more worrisome is that the Club effort did not decrease after 2007, but the numbers seen did, suggesting a real decline 2007-2009.
Very few individuals, usually singles, were reported 1990 – 2002. After that, known locations in Wayland and Concord were searched in multiple visits every year, and some previously unknown locations in these and other towns were found. An annual club trip to the Wayland area was held each year 2001-2010, with multiple pre-trip trips. The high counts on some of these trips are noted below.
Numbers at known locations seem to have declined in 2008 and 2009. In 2007, the average number of Bronze Coppers per report of that species had increased 159% relative to the average for the preceding years back to 1994. The number of reports of this species, and the maximum number reported, also increased in 2007 relative to prior years. However, in 2008 and 2009, the average number per report decreased relative to the average for preceding years (Nielsen, Season Summary, MB 2008-2010, Nos. 30, 32, 34). Preliminary numbers from 2010 look to be back up, however.
Separate analysis by Greg Breed of Harvard Forest, using list-length analysis, indicates an approximately 400% increase in this species' detectibility in Massachusetts between 1992 and 2010 (Breed et al. 2012).
State Distribution and Locations
Map 15: MBC Sightings by Town 1992-2010
The 1986-90 MAS Atlas found Bronze Coppers only in or near the Sudbury River drainage (Concord, Sudbury, Millis), and in Essex County (Ipswich, Newburyport (Plum Island), West Newbury). There was one record from western Massachusetts (Pittsfield) and one from central (West Boylston). There were none found in southeastern Massachusetts or in the Connecticut River valley.
Map 15 from MBC records 1992-2010 confirms and expands the Atlas distribution, in particular showing Bronze Copper to be more widespread in the Berkshires than had been thought. Singles have been found in Egremont, Stockbridge, Cheshire, and Windsor, and also possibly Sheffield, Pittsfield, and Adams, judging from the NABA count reports. Bronze Copper has been found in nearby Charlemont (Franklin County), in the upper (Greenfield), and the lower (Longmeadow), but not the central parts of the Connecticut River valley.
Bronze Copper is not common in central Massachusetts: singles have been found only in two towns, Princeton (1995) and Brookfield (1998). But in the greater Boston area, the strongholds in Concord, Wayland and Lincoln remain, and there are now several reports from Boston’s newly-created habitat at Millennium Park (2008; 2010). In Norwood/Milton, Glassberg (1989:34) listed Fowl Meadow as an active location, but there have been only two recent reports (M. Arey, 2009 and 2010).
In Essex County, Bronze Copper has been reported only once from Plum Island (R. Hildreth, 3 individuals, 9/14/2003), but good searches of Plum Island have not been made since. Singles were found in 2008 and 2009 in a Newbury yard near Plum Island. Bronze Copper was reported in three years (2002, 2003, and 2012) at Ipswich River WS in Topsfield, around polygonum at the edges of the Ipswich River. In 2009, 2010, and 2011 Bronze Copper was found at Appleton Farms in Ipswich, where it was documented photographically in 2011 by Howard Hoople (see http://www.flickr.com/photos/hghoople/6201148117/ taken Oct 1, 2011). Bronze Copper seems established, but rather scarce, in Essex County.
Bronze Copper does not occur in southeastern Massachusetts: there are no MBC, Atlas, or historical records. Mello and Hansen (2004) do not list it for Cape Cod, and it is not found today on the Vineyard (Pelikan 2002) or Nantucket (LoPresti 2011). Nor was it on these islands in the 1940's, although it may have been present on one or both of the islands prior to 1900 (Jones and Kimball 1943: 197, citing the pre-1900 Bolter collection).
The highest counts and the most frequent reports still come only from the Sudbury River drainage. In MBC records the high count from Wayland Community Gardens was 8 on 10/6/2003, T. Murray; from Concord Nine Acre Corner field was 19 on 10/9/2006, E. Nielsen; from Sudbury Community Gardens was 10 on 9/25/2010 E. Nielsen et al., and from Moore Road Sedge Meadow CA Wayland was 22 on 9/25/2010 E. Nielsen et al. (although M. Arey reported numbers as high as 46 on 9/3/2007 [masslep 10/1/2008]).
COLLECTORS PLEASE NOTE: specimens OF THIS SPECIES should NOT be collected without a permit for scientific research. The purpose of the research and the institution where the specimen(s) are to be deposited should be specified.
Broods and Flight Periods
MBC sight records show two flight periods: a small flight mid-June to mid-July, and a larger flight mid-August to mid-October (Nielsen 2008). There are undoubtedly at least two broods here, as in Connecticut (O’Donnell et al., 2007), although in Ohio there are three (Iftner et al. 1992).
For the period 1992-2010, the four earliest MBC sighting dates are 6/7/2009 Concord Great Meadows NWR, S. Jaffe; 6/8/2010 Ipswich Appleton Farms, H. Hoople; 6/9/1995 Charlemont, D. Potter; and 6/12/2008 Boston Millennium Park, B. Bowker. The three latest sightings are 10/21/2007 Wayland Community Gardens, J. Forbes; 10/19/2006 Concord Nine Acre Corner, T. Whelan; 10/13/2003 Wayland Community Gardens, E. Nielsen.
The extreme dates reported during the Atlas period are similar ---15 June and 21 October 1990, Concord (Middlesex Co.), R. Walton. There is not enough information at present to indicate any trend toward earlier emergences or later flight dates.
Despite an upward population trend here, this species should be a conservation priority in Massachusetts given the regional context of decline. The status of Bronze Copper in the northeast has been the subject of concern for some time. In Connecticut it is a state species of special concern, rank S2. The 1995-99 Connecticut Atlas found it local and rare, with only 12 project specimens compared to 31 pre-project. It is thought to be declining due to loss of pastures and wet meadows through development or succession.
The species has especially declined in New Jersey (Gochfeld and Burger 1997:146-7). In 2002 New Jersey adopted a list of Endangered, Threatened and Special Concern species of butterflies, with Bronze Copper listed as Endangered. But after an absence of sightings since 1996, a few were seen in 2007 and 2008 (Wander and Wander 2009).
As far back as 1989 Glassberg suggested that although the species had always been local and uncommon in the northeast, it appeared to have declined over much of the area (Glassberg 1989). Cech (2005) wrote that during the decade he spent preparing his book he encountered Bronze Coppers just twice, finding them absent at many formerly reliable sites. He concludes, “This is a troubled species that needs stewardship in our increasingly urbanized region.”
Bronze Copper is a northerly species, which ranges across Canada, but south only to Maryland on the east coast of North America. It may be sensitive to climate warming (Table 6). In Maryland and Pennsylvania, partial third broods have been reported (Opler and Krizek 1984). Research on brood timing in Massachusetts is needed.
Bronze Copper should benefit from the preservation of sedgy wet meadow habitat, kept open through light grazing or occasional mowing. Several writers have noted that it apparently tolerates some degree of disturbance in wet meadows; for example in northern New Jersey it been found in agricultural upland areas within the floodplains of larger streams (Gochfeld/Burger 1997; Wander and Wander 2009). At Appleton Farms in Ipswich Massachusetts it has been found in conjunction with moderately grazed wet meadows. Coexistence with non-industrial agriculture may be possible.
The Massachusetts populations in Wayland and Concord are in large sedge-dominated meadows, subject to periodic flooding and to human disturbance such as mowing and plowing. One area at Nine Acre Corner periodically serves as a parking lot for golf tournaments. The town of Wayland in 2012 allowed farmers to plow up the important Sedge Meadow Conservation Area to grow corn. Bronze Coppers at this site survived in reduced numbers only because a strip was left unplowed for "wildlife."
The core Bronze Copper population in the state is in Wayland, Concord, and Sudbury. Some may be on the federally-protected Great Meadows NWR (amazingly, it is not known how many, because no full searches have been made), but all other known populations are on vulnerable sites. The population in these three towns needs to be estimated and systematically monitored. MBC counts often show quite low numbers.
The NatureServe ranking for Bronze Copper in Massachusetts is S2-S3: between “imperiled” and “vulnerable.”
© Sharon Stichter 2010, 2011
page updated 9-24-2012
Species of Conservation Concern
ABOUT BOM SPECIES LIST BUTTERFLY HISTORY PIONEER LEPIDOPTERISTS METHODS