ABOUT BOM SPECIES LIST BUTTERFLY HISTORY PIONEER LEPIDOPTERISTS METHODS
The Butterflies of Massachusetts
18 Acadian Hairstreak Satyrium acadica (W. H. Edwards, 1862)
The Acadian is a rather special hairstreak. Unlike our more common Satyrium hairstreaks, Edwards’, Striped, and Banded, which are forest, forest-edge, or dry scrub dwellers, the Acadian is associated with shrubby willows in open wet meadows and streamsides. It was probably one of the earliest re-colonizers of New England during the post-glacial Pleistocene. Today it is a northerly species only, lacking the southeastern U.S. distribution shown by most of our other Satyrium hairstreaks (maps in Opler and Krizek 1984; Cech and Tudor 2005). A recent study suggests it may be declining in Massachusetts (Breed et al. 2012). Its notable decline further south, at its former southern limit in New Jersey (Gochfeld and Berger 1997: 149) may be due to climate warming as well as habitat loss.
Photo: Woburn, Massachusetts, H. Hoople 7-1-2011
Acadian Hairstreak was apparently not common, and perhaps even rare, at the turn of the century here, even though one might think it would have benefited from an increase in willows during the agricultural era. Scudder cites hardly any New England locations for it, in contrast to the Banded, Striped, Edwards’, and Coral Hairstreaks. He had specimens from only two Massachusetts areas, Williamstown and Cape Cod, which he himself had taken around thickets fringing streams (1889: 901). He did list it as “known to occur in Essex County” (Scudder 1872). T. W. Harris does not mention Acadian, nor did he have any specimens in his 1822-1850 collection (see Index). In fact, there are no 19th century Massachusetts specimens in the Harvard Museum of Comparative Zoology, but Maynard (1886) said that he had “two specimens of this rare species before me which were taken in the vicinity of Boston, but I have never met with it living, in fact it does not appear to be at all common anywhere.”
Thirty years later, Farquhar (1934) adds only Amherst (C.S. Minot; specimen is at Boston Univ.), and a doubtful specimen from Dover, to Scudder’s list of Massachusetts locations. Root and Farquhar (1948) list no specimens in their review of the Andover region, and Jones and Kimball (1943) do not list it for Martha's Vineyard or Nantucket. But Acadian Hairstreak may have become more common in the 1960's and 1970's, according to Lepidoperists' Society and other records. S. A. Hessel found two specimens in Egremont on July 7, 1962, which are now in the Harvard MCZ. Charles. G. Oliver listed it in 1967 as one of three hairstreaks, the others being Banded and Striped, which were common in dry old fields on Asclepias in the Acton area. D. Willis reports Acadian in 1973 and 1974 in the Holliston-Sherborn-Framingham area, saying that he took 12 specimens in 1973. And Patrick Carey reports it in 1975 as “fairly common in fresh condition in a dry field near the CATY tower in South Hadley on June 30” (Lep Soc. Seas. Sum. and Correspondence, 1965-1975).
Host Plants and Habitat
Acadian Hairstreak's larval hosts are many willows, including Black Willow (Salix nigra), Pussy Willow (Salix discolor), Silky Willow (Salix sericea), and Beaked Willow (Salix bebbiana), all of which are native to, and found in, every county in Massachusetts (Dow Cullina et al., 2011). These willows, especially Black and Pussy, are widespread in the state, so the scarcity of the butterfly is somewhat surprising, and may have to do more with climate or some other aspect of habitat, such as the availability of nearby nectar sources or the presence of suitable ants. The butterfly is almost always associated with willow-bordered wetlands, such as wet meadows and streamsides, but may often be found nectaring in nearby, drier sites, such as a dry rocky hilltop in Woburn where Acadians nectar on New Jersey Tea (see photo above).
Relative Abundance Today
Both MBC and earlier Atlas records rank Acadian Hairstreak as Uncommon (Table 5). The Atlas found it in 30 out of 723 blocs searched.
Acadian Hairstreak may be declining in Massachusetts, or at least is subject to great population fluctuations at its few known locations. Chart 18 shows an overall decline between 1992 and 2009, but this result depends greatly on the high index reading for 1992, which mainly reflects high counts at the two best-known colonies: Bristol County (mainly New Bedford area) (41) and Pittsfield (26). Then in succeeding years numbers at both colonies dropped, but showed a resurgence in 2004 and 2005.
However, a separate analysis of the same 1992-2010 MBC data, using list-length rather than number of trips as a proxy for effort, and does not rely on counts of individual butterflies, did find a statistically significant 82.5% decline over these years. In that study, Acadian Hairstreak had the second largest decline among all Massachusetts species in detection probability. It, Aphrodite Fritillary and Atlantis Fritillary are the three species with the greatest declines. All are northern-based species (Breed et al., 2012).
The number of individuals per total trip reports shown in Chart 18, as well as the number of sightings per total trip reports containing that species (chart not shown), both show the same pattern: a marked increase in 2004 and 2005, and a downward trend 2005-2009.
Chart 18: MBC Sightings per Total Trip Reports 1992-2009
A decline in 2008 and 2009 from the highs of 2004 and 2005 is also evident in calculations of percentage decline from prior years. In 2007 the average number of Acadians per report of that species increased 43% compared to the average for preceding years back to 1994. But in 2008 and 2009 the average declined 25% and 19% respectively, compared to prior years. The number of reports of this species also declined in each of these three years compared to prior years. The declines are especially notable in contrast to the increases for Coral Hairstreak. (Nielsen, Season Summary, MB 2008-2010, Nos. 30, 32, 34).
State Distribution and Locations
Map 18: MBC Sightings by Town, 1992-2009
MBC 1992-2009 records show Acadian Hairstreak in 36 out of 351 towns (Map 18). The MBC map shows three main areas for Acadians: the Berkshires, the Connecticut River valley, and from the Worcester area through eastern and southeastern Massachusetts. This hairstreak has not been found in lower Plymouth County, or on Martha's Vineyard or Nantucket.
The only report from Cape Cod (not shown on this map) is from Sandwich, Massachusetts Military Reservation, where a recent survey (7/16/2011, E. Nielsen and P. Trimble) found 43 Acadian Hairstreaks amid many Edwards' and Banded. This area is closed to the public. This is the first report of Acadian Hairstreak from Cape Cod since Scudder's day, and this colony ought to receive monitoring and protection.
The MBC map adds to the distribution picture produced by the earlier MAS Atlas by showing that Acadian is-- or at least was-- well-distributed in central, southern and northern Berkshire County and in the Connecticut River valley. It had in fact been known from the Berkshires for some time: S. A. Hessel documented Acadian in 1962 in Egremont, and David L. Wagner and others collected several specimens in Sheffield at Schenob Brook fen on 7/10/1993. Wagner also found it at Ashley Falls near Sheffield on July 14, 1996. In “the valley” it was also historically known: S. Carey found “numerous S. acadica” in a dry field, South Hadley, June 30, 1975 (Lep. Soc. Seas. Sum. 1975).
On the Central Berkshire NABA Counts, Acadian Hairstreak has been found in good numbers nearly every year from 1992-2011; a high count of 134 was reported 7/17/2005, and the next highest total was 53 in 2007. But there were only 26 in 2009, 12 in 2010, 10 in 2011, and 1 in 2012 (but 24 two weeks earlier), so numbers appear to be declining. The Southern Berkshire NABA Counts found Acadian every year 2003-2008 in small numbers, but did not report it in 2009, 2010, 2011 or 2012. The Northern Berkshire NABA Counts found Acadians in very small numbers in 1994, 1995, 2004, 2007, 2011 (including Mt. Greylock), and 2012 (1, Williamstown, B. Zaremba and P. Weatherbee). From Count data, numbers in the Berkshires, as in the state as a whole (Charts 18), seem to be in a downward phase.
For the Connecticut River Valley, contemporary records are very sparing. There is a record from Chicopee, July 2, 1994 (M. Mello, pers. com.). Other reports come from Greenfield (1, 7/7/2001, Central Franklin NABA Count), Northampton (1, 7/13/2000, T. Gagnon), and the Springfield area (4, 7/15/1995, but 1, 7/15/1999, Lower Pioneer Valley NABA Counts). There are NO records for "the valley" more recent than these. For the central towns around the Quabbin Reservoir, MBC, like the Atlas, has no Acadian records, although it seems likely the species would occur there.
For the Worcester area, and to the east and south of Worcester, including northern Bristol County, MBC, like the Atlas, does have records, but these are all from the 1990's and are of very low numbers (1-2 per report). The most recent records are from 2008: 2 found on the Blackstone Valley NABA Count and 1 on the Northern Worcester NABA Count. These counts have not reported Acadians since then.
Acadian Hairstreak does still occur in a well-known colony in southern Bristol County near New Bedford (max. 54 individuals 7/17/1994; but 12 on 7/19/2005). This colony was reported from the 1980s through 2005, but none were reported between 2005 and 2012, when the colony apparently declined markedly as a result of a well-intentioned wetland restoration project. But finally, in 2012, a dozen Acadian Hairstreaks were re-located at that site (July 6, 2012, M. Mello), nectaring on dogbane and narrow-leaved Mountain Mint. There is also another small colony in the Dartmouth area, from which one was reported on 7/8/2012, M. Mello. MBC records do not show Acadian Hairstreak to be “common” in Bristol County, as the Connecticut Atlas put it; MBC and NABA records refer solely to these two small colonies.
For Essex County, MBC does not have any Acadian records, and there are apparently none since 1990, when the MAS Atlas found it in Beverly (7/14/1990, T. French), Haverhill (7/4/1989, T. French), and nearby Reading (7/8/1989, S. Goldstein). These areas should be re-checked.
There are no MBC reports from Cape Cod outside of the Sandwich Military Reservation, and the Atlas did not find it on the Cape. Mello and Hansen (2004: 38) cite a few possibly appropriate habitats. Scudder had reported it historically from the Cape, but that specimen is not in the MCZ today, nor are any others from the Cape.
Acadian has not been reported from Martha’s Vineyard or Nantucket by MBC or the Atlas or other sources (Pelikan 2002; LoPresti 2011). Historically, Jones and Kimball (1943) do not list it as present on these islands.
NOTE TO COLLECTORS: Due to its uncommon and possibly declining status here and in other states (e.g. New Jersey), collectors should refrain from taking specimens of this butterfly. Some locations have been omitted from the discussion above to deter amateur collecting.
Broods and Flight Period
All of our Satyrium hairstreaks have a single flight mainly in July, and the Acadian is no exception. Peak reports are usually the second week in July (http://www.naba.org/chapters/nabambc/flight-dates-chart.asp). However, in 2012 the peak numbers at the Pittsfield colony were recorded on June 24, and declined after that (T. Gagnon, pers. com.).
First Sightings: In the 20-year period 1991-2010, the earliest "first reports of the year" in MBC records are 6/21/2010 Woburn, R. and S. Cloutier; 6/21/1998 Grafton D. Price and D. Small; 6/22/1991 Worcester BMB, T. Dodd; 6/27/2004 Woburn, M. Rines; 6/29/1996 Clinton/Sterling T. Dodd; and 6/30/1995 Sherborn T. Dodd. Thus, in 6 of the 20 years, Acadian Hairstreak was seen before July 1. In 2012, the first sighting of Acadian Hairstreak was also rather early: 6/23/2012, Woburn, S. Moore et al. But the record early date remains 6/21/2010.
Flight Time Advancement: A century ago Scudder wrote that this butterfly "generally appears about the 10-15 July, although it sometimes occurs as early as the very end of June" (1899: 902). The geographical latitude to which Scudder was referring is not clear. Acadian Hairstreak's first appearance in Massachusetts is now often in the third or fourth week of June, so the flight period might have advanced since Scudder wrote. However, a 2012 study at Boston University, which combined Atlas and MBC sighting data for 19886-2009 showed that Acadian Hairstreak had not advanced its flight time over this time period (Graph 18) (Polgar, Primack, et al. 2013; graph courtesy of Caroline Polgar).
Graph 18: Change in the first 20% of all Acadian Hairstreak sightings, 1986-2009
The slope is only weakly negative, and the R-square value shows that virtually none of the variance in the first Acadian Hairstreak sightings is explained by year alone. In this linear regression p=0.67, so the result is not significant. Nor did the addition of museum specimens show any advance in flight time over the long time period since 1896, but the small sample of dates for this butterfly undoubtedly limited the results for both time periods.
Last Sightings: In the 20-year period 1991-2010, the latest MBC flight dates are 8/12/1992 Easton, L. Lovell; 7/26/1997 Pittsfield T. Tyning et al; 7/27/1995 Savoy D. Potter; and 7/25/1993 Worcester BMB T. Dodd. The early and late flight dates are virtually the same as those reported during the Atlas period. The years 2011 and 2012 did not set any new late dates. Scudder's rather vague flight ending date was "until the end of the first week in August, perhaps longer" (1899: 902). In all of 22 years, MBC records contain only one sighting in August -- that from Easton noted above. Scudder's dates may be meant to include localities further north of Massachusetts.
Outlook
The Acadian Hairstreak's center of gravity is northern damp meadows; it is most secure in the northern mid-continent areas of the U.S. and Canada. In the east, it reaches the southern edge of its range in Pennsylvania and New Jersey, and it is vulnerable in these areas, where climate warming may induce a withdrawal westward and northward.
Acadian Hairstreak has already undergone a decline in New Jersey. Despite repeated searches, it has not been seen there since 2006, and is now under state review (Wander and Wander, 2009). Acadian Hairstreak may also be declining in Connecticut. In the 1990-95 Connecticut Atlas, there were only 19 project specimens, compared to 41 pre-project specimens. Also, it appeared to be gone from some former areas in the eastern part of the state. In Rhode Island, Acadian is ranked S2S3 or “imperilled” (NatureServe 2010).
Acadian Hairstreak is listed here as a Species of Conservation Concern in Massachusetts. It is already scarce on the southeastern plain, and if climate warms further, we could see a range contraction northward and westward, and contraction to higher elevations, in the state (Table 6). Climate warming appears to be the main threat, but urban/suburban development, forest re-growth, pesticide spraying, and indiscriminate collecting can also adversely affect this species. Very few of the known colonies are on protected land.
The four largest known Acadian Hairstreak colonies-- Mass. Military Reservation, New Bedford, Woburn, and Pittsfield --should be protected from development, should be monitored yearly, and should be managed to deter forest succession and preserve host plant willows. Searches need to be undertaken to locate and protect the lesser-known breeding areas in the northern Berkshires. Acadian Hairstreak’s 2010 NatureServe rank is S4 in Massachusetts, but this urgently needs review given the experience in nearby states and the indications of decline here.
© Sharon Stichter 2010, 2011, 2012, 2013
page updated 3-13-2013
ABOUT BOM SPECIES LIST BUTTERFLY HISTORY PIONEER LEPIDOPTERISTS METHODS