ABOUT BOM SPECIES LIST BUTTERFLY HISTORY PIONEER LEPIDOPTERISTS METHODS
The Butterflies of Massachusetts
78 Horace's Duskywing Erynnis horatius (Scudder & Burgess, 1870)
Horace’s is the less common of our two larger duskywings, Juvenal’s and Horace’s. Its range overlaps with that of Juvenal’s Duskywing, but does not extend as far north (Opler and Krizek 1984; Cech 2005). It is more common in southeastern states than in Massachusetts.
Scudder and Burgess described and named this interesting species in 1870, and Scudder's 1868 type specimen from "Massachusetts" is in the Harvard MCZ. But Scudder actually had very little information about its distribution in New England, noting that it had frequently been confused with Juvenal’s. He reports that it had been found only in the southern half of New England, and for Massachusetts lists specimens from Foxboro, Andover, Boston and Middlesex Fells in the east, and Amherst in the west. Horace's was not among the five species of Erynnis which ace collector F. H. Sprague found at Wollaston (now Quincy) in 1878, but he did find it later, July 25, 1897, further south in Sharon (Sprague 1879; specimen at BU museum). At the turn of the century Horace's Duskywing was probably less common in Massachusetts than it is today.
Photo: Great Blue Hill, Canton, Mass., E. Nielsen, August 1, 2009
Horace’s may have become more common in the twentieth century (Table 2). Farquhar’s comprehensive 1934 review of specimens adds finds from Milton (Blue Hills), Sharon, Melrose (Gypsy Moth Lab), Stoneham, and Westwood, and as far north as Phillipston in central Massachusetts. Yale Peabody Museum has specimens from Canton (17 July 1921 P. S. Remington), Sherborn (23 May 1921, no coll.), Lynnfield (27 May 1921, no coll.), and Fall River (4 May 1936 W. P. Rogers), as well as Springfield (Dimmock, undated). D. Lennox collected it in 1949 in Waltham; M. Mello collected it in New Bedford in 1962.
On Martha's Vineyard Horace's Duskywing was "not rare" in the 1930's and 1940's, with two flights, May and then July-August (Jones and Kimball 1943). Yale Peabody Museum has 14 Vineyard specimens by F. M. Jones, spanning the years 1939-45, with species determined by J. M. Burns. On Nantucket Kimball and Jones (1943) report at least one specimen, from May 20, 1940.
Through the 1970’s and 1980’s, there were many reports of Horace’s in the annual Lepidopterists' Society Season Summaries, as collectors were concerned to document the northern edge of its distribution. Edward M. Peters found it in Carlisle in 1970, Dave Winter found it in Medway in 1973 , Darryl Willis found it at the Sherborn power line in 1974 and 1975, and Dale Schweitzer documented it again in Lynnfield and in Medford Middlesex Fells in 1986-1988 (specimens in Yale Peabody Museum).
Gochfeld and Burger suggest for New Jersey that Horace’s “apparent rarity at the turn of the century” might be simply the result of confusion with Juvenal’s and Wild Indigo Duskywings. Still, in that state it has certainly increased since then, along with the Wild Indigo, while Dreamy, Mottled, Columbine and Persius Duskywings have decreased (1997:223). The picture seems much the same for Massachusetts.
Horace’s Duskywing is at the northern limit of its range in Massachusetts, so it is of interest to establish its precise distribution here. There have been no Horace’s found so far by the ongoing Maine Butterfly Survey (MBS 12/2011; http://mbs.umf.maine.edu/). In Vermont there are no historic records, the first and only specimen being found in 2007 in southeastern Vermont (McFarland and Zahendra 2010). In New Hampshire there is one pre-1990 record from one southern county (NH Nat Heritage 2010).
Host Plants and Habitat
Horace’s known native host plants are various oaks, in our area probably primarily Scrub Oak (Quercus ilicifolia), Red Oak (Q. rubra), and White Oak (Quercus alba), but also possibly Black Oak (Q. velutina) and Post Oak (Q. stellata) (Scott 1986; Allen 1997). All of these occur in Massachusetts, though ilicifolia is found mainly in barrens habitats, and stellata is native only to the Cape and Islands (Sorrie and Somers 1999). D. Schweitzer reported Horace’s ovipositing on Quercus alba in Middlesex Fells in Medford in 1986 (Lep. Soc. Seas. Sum. 1986). In 2009, photographer Sam Jaffe found Horace’s caterpillars on scrub, black and red oak on Great Blue Hill in Canton and in West Bridgewater (Jaffe 2009).
Like Juvenal’s Duskywing, Horace’s is not confined to barrens habitats, but can be found in almost any kind of woods or woods edge which has both oaks and an adequate supply of nectar to support its two broods. North of New Jersey, it prefers dry, rather open, rocky or sandy oak woods and pine barrens. Power line cuts, woods paths, and even gardens and parks are possible habitats. Schweitzer reports that Horace’s prefers to oviposit on small oaks, even seedlings. But Schweitzer (NatureServe 2010) also notes that Horace’s is absent from the more pristine sections of the New Jersey pine barrens due to the lack of summer nectar. Thus suburban gardens and parks may enhance natural habitats. Horace’s has been seen nectaring on dogbane, goldenrod, and mints.
Relative Abundance Today
The MAS Atlas account found that Horace’s was “frequent to common in the Boston area, and probably also in the southeastern counties, during the mid- to late 1980‘s." But the Atlas had found the species only east of Worcester County, and only in 35 out of 723 atlas blocs, and on that basis Horace’s should not have been described as “Common” statewide. MBC records 2000-2007 rank its relative abundance on the low end of ‘Uncommon,” more on a par with Sleepy Duskywing than with the “Uncommon-to-Common” Juvenal’s Duskywing (Table 5).
Horace’s is an example of a more southern-based species whose numbers are probably on the increase here. The trend has been a strong and fairly steady increase between 1994 and 2008 in annual sightings per total trip reports, but a drop in 2009 (Chart 78). The absolute (unadjusted) number of individuals reported (not shown) actually shows a steady rise 1992- 2009. In some part these results may be attributable to Club members’ increasing ability to accurately identify this species. The high readings shown in 1992 and 1993 in Chart 78 are an artifact of the smaller number of total trips in those years, and should not be given much weight.
Chart 78: MBC Sightings per Total Trip Reports 1992-2009
In 2007 and 2008, although not 2009, the average number of Horace’s per report of that species increased 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 and 2008, but not 2009, relative to prior years (Nielsen, Season Summary, MB 2008-2010, No. 30, 32, 34).
State Distribution and Locations
Map 78: MBC Sightings by Town 1991-2010
MBC records confirm the southerly and easterly distribution in our state (Map 78). The great majority of records are from southeastern and south central Massachusetts. Horace's is reported regularly but infrequently from Essex County north of Boston, and there are very few records from northern Worcester County except for Petersham. There are no reports from Franklin or Berkshire Counties. On the NABA Counts, it is often reported from the Bristol and Cape Cod Counts, and from the Blackstone Valley Count, but has never been reported from the Northern Worcester, Central Franklin, or any of the three Berkshire Counts. The distribution described here accords with other published maps (Opler and Krizek 1984; Cech 2005).
The northernmost recent sighting, not yet on Map 78, is Newbury Martin Burns WMA, where Horace's Duskywings, both female and male, were extensively photographed by B. Zaremba on 7/24/2011; photos available at http://www.pbase.com/bo_z/horaces_duskywing_series . These photos re-confirm the 1980's MAS Atlas report from Newbury, by T. French, 7/19/1987. The northernmost location now shown on Map 78 is North Andover Weir Hill TTOR, 4/20/2010, R. Hopping, and two other 2010 reports from North Andover. There are also historical reports from North Andover and Andover, and reports from Chelmsford (e.g. 7/28/2011, 2, power line, B. Bowker).
The westernmost sightings so far are from Northampton community gardens: 1 worn female seen on 8/21/2008 by Tom Gagnon, and another on 9/4/2010 (and 8/7/2011). There are also sightings in “the valley” from East Longmeadow (5/6/1998, K. Parker), and Hampden (5/14/1995 G. Howe). There is an Atlas report from Southwick (5/9/1989 T. Fowler), and historical reports from Amherst (Scudder), Montague and Granby (Schweitzer in Atlas). These reports need re-confirmation today. In general, Horace’s does not appear to be common in “the valley.”
Horace's Duskywing has been reported from 61 towns as of August 2011. Towns with reports which are not yet shown on the map are Belmont, Carver, Holden, Medford (Middlesex Fells), Newbury (Martin Burns WMA), Princeton, Raynham, Sandwich, and Yarmouth.
Horace's Duskywing has been reported occasionally from Martha's Vineyard in MBC records, but only three times in 20 years on the Vineyard NABA Counts. The Vineyard checklist ranks this species as "rare" today, despite F. M. Jones' historical records (Pelikan 2002). The single historical record for Nantucket leads observers to believe that Horace's Duskywing is possible on that island, but there are no recent MBC or Atlas records.
The largest numbers reported from any one site have consistently come from Canton Great Blue Hill, with maxima of 30, 7/16/2007, F. Model and 12, 7/6/2008, E. Nielsen. There are several other reports of around 10 from Great Blue Hill. Other productive sites for Horace’s Duskywing have been Plymouth/Carver Myles Standish SF max 6 on 5/24/2008 MBC (Murray+Nielsen); Sherborn power line max 2 on 8/20/2008 B. Bowker; Milford power line max 4 on 7/17/1999 R. Hildreth, T. Dodd, B. Cassie; Newbury Martin Burns WMA max 4 on 7/24/2011, B. Zaremba; Woburn Horn Pond Mountain max 2 on 7/4/2007 E. Nielsen; Worcester Broad Meadow Brook WS max 5 on 5/12/2001 G. Howe; and Yarmouth Bayberry GC power line, max. 5, 8/6/2011, J. Dwelly. Schweitzer reports Medford Middlesex Fells as a good location in the mid-1980s; there is a recent report of 1 on 5/2/2010 M. Arey, but further visits to this formerly productive location are needed.
Broods and Flight Time
Two broods and a long flight period are shown in MBC records. The first brood flies in May, and the second mostly in July. The first flight is less often reported, perhaps because of confusion with Juvenal's Duskywing. The bulk of sightings come in the last three weeks in July, when Horace's may be more confidently identified, since Juvenal's is not flying. See the MBC flight chart, at http://www.naba.org/chapters/nabambc/flight-dates-chart.asp.
In the 25 years of combined Atlas and MBC records (1986-2010), seven of the first reports of Horace’s have come in late April or the first week in May (5/1-5/7). The six earliest sightings during the Atlas and MBC years are 4/20/2010 North Andover Weir Hill R. Hopping; 4/20/1986 M. Mello New Bedford (Atlas); 4/28/1999 Topsfield Ipswich River WS F. Goodwin; 5/3/1987 Rehoboth K. Anderson (Atlas); 5/6/1998 East Longmeadow K. Parker; 5/7/2001 Lexington B. Wright; and 5/7/2006 Sherborn power line, B. Bowker. Another six first sightings are in the second week of May (5/8-5/14). (In 2011, the first sighting was 5/6/2011 Plymouth Myles Standish SF, S. Moore.)
It would be useful to compare these dates with those reported by Scudder 100 years ago, but unfortunately Scudder did not have very precise information. He thought that Horace’s probably appeared about the same time as Juvenal’s (which would be early May at that time), but the earliest capture he mentions is on May 18 at Andover, Mass. Thus there is no strong evidence for any trend toward earlier sightings.
Horace’s Duskywing begins flying later than Juvenal’s Duskywing according to MBC records. Whereas the earliest reports of Horace’s are 4/20 or 4/28 in Atlas/MBC records, the earliest reports of Juvenal’s in these records are on 4/10.
But there may be a trend toward later sightings. The latest date that Scudder mentions is August 4, when “at Amherst Notch I caught or saw a dozen or two” (1889:1489). There were no September reports during the Atlas years, but in the 20 years 1991-2010 six of the ‘last sighting’ dates are in September. These are 9/24/2010 Chelmsford power line B. Bowker; 9/19/1999 Waring Field Rockport T. and C. Dodd, D. Savich; 9/18/2006 Marblehead Legg’s Hill K. Haley; 9/12/2004 Canton Great Blue Hill M. Champagne; 9/3/2000 Easton B. Cassie; and 9/3/2008 Uxbridge Blackstone River SP B. Bowker.
Before 1999, no September reports have yet been found, except for one from the 1930’s (9/20/1936 Westport, D. Lenox) cited in the MAS Atlas. In the Atlas account, D. Schweitzer suggests that September reports may indicate a partial third brood here. In the Gulf states, there are 3 full broods (Opler and Krizek 2004).
If climate warming proceeds in our state, it is likely that Horace’s Duskywing numbers will increase (Table 6). Horace’s is currently ranked S3 or “apparently secure” in Massachusetts (NatureServe 2010).
The increase in abundance of Horace’s Duskywing in Massachusetts is opposite to the finding of the Connecticut Atlas, where there were fewer project records than pre-project records (49: 4), and where the species is ranked S2 "imperiled," and is of special conservation concern, since scrub oak barrens habitats are becoming increasingly restricted and fragmented (O'Donnell et al. 2007:58; 294; NatureServe 2010).
© Sharon Stichter 2010, 2011, 2012
page updated 2-17-2011
ABOUT BOM SPECIES LIST BUTTERFLY HISTORY PIONEER LEPIDOPTERISTS METHODS