Journal of the Lepidopterists’ Society
67(4), 2013, xx–xx
USE OF TWO OVIPOSITION PLANTS IN POPULATIONS OF
EUPHYDRYAS PHAETON DRURY (NYMPHALIDAE)
Additional key words: Baltimore Checkerspot, iridoid glycosides, Vermont
The Baltimore Checkerspot, Euphydryas phaeton
Drury (Nymphalidae: Melitaeini), is a univoltine species
that ranges from Georgia in the south, north to Maine
and southern Canada and west to Kansas (Scudder
1889; Masters 1968; Harris 1972). Its native host plant is
White Turtlehead, Chelone glabra L. (Plantaginaceae),
a denizen of marshy, wetland habitats. In the Ozarks,
another subspecies, E. phaeton ozarkae Masters, was
described as somewhat different in appearance and
using the oviposition plant Aureolaria ﬂava (L.) Farw.
(Orobanchaceae) (Masters 1968). Just over 30 years ago,
a third oviposition plant was described for E. phaeton,
the introduced weed, Ribwort or Narrow-leaved
Plantain, Plantago lanceolata L. (Plantaginaceae)
(Stamp 1979). Plantago lanceolata was introduced into
North America about 200 years ago (Cavers et al. 1980)
and has been incorporated into the diets of many native
North American herbivores (Robinson et al. 2002).
These three different species of oviposition plants are
united by the presence of a particular group of plant
chemical compounds, the iridoid glycosides (Bowers et
al. 1992; Belofsky et al. 1989). Indeed all host plants of
E. phaeton contain iridoid glycosides (Bowers 1980;
Bowers et al. 1992).
Euphydryas phaeton has been declining in numbers
in many areas such as Maryland and Rhode Island
(Durkin 2009); however, in Vermont, there are many
healthy colonies. Speciﬁcally, the recent Vermont
Butterﬂy Atlas Project has documented E. phaeton
populations at nearly 200 sites (McFarland and
Zahendra 2010). Furthermore, the use of Plantago
lanceolata has allowed some populations to get
extremely large; for example, a recent survey of adults
from a population on June 19, 2010, in Bristol, Rhode
Island, in a ﬁeld of approximately seven acres, revealed
a population estimate of over 3,200 individuals of E.
phaeton (4th of July butterﬂy count Rhode Island,
2010). A careful search of this site and surrounding
areas revealed no evidence of C. glabra. More recently,
during the 2012 butterﬂy count in Rhode Island,
another large population (over 1000 individuals
counted) was located on private land near Little
Compton (2012 4th of July butterﬂy count Rhode
Typically, only a single plant species is used as an
oviposition plant by a single population of Baltimore
Checkerspots, although post-diapause larvae may feed
on a variety of plant species, including Penstemon
(Plantaginaceae), Ash (Fraxinus, Oleaceae), Viburnum
(Adoxaceae), false foxglove (Aureolaria) and
honeysuckle (Lonicera, Caprifoliaceae). For example, in
New York (Stamp 1979) and Rhode Island (Bowers and
Schmitt 2013), populations of E. phaeton use solely P.
lanceolata for both oviposition and larval feeding. Other
populations using exclusively P. lanceolata also likely
occur. Most populations, however, still use C. glabra as
the sole oviposition plant.
Here we report the occurrence of two populations in
Vermont that use both C. glabra and P. lanceolata as
oviposition plants at the same sites (Figures 1 and 2). At
both sites, ovipositing E. phaeton females were observed
using both plant species on the same day (although we
did not follow individual females) in 2011 and 2012
(Figure 1 and 2). The two sites were 1) Clark,
Washington County (Figure 1); 2) Connor, Washington
County (Figure 2). There are likely to be other E.
phaeton populations that use both species for oviposition
as well because many Vermont wetlands where C. glabra
occurs are located in or near agricultural landscapes,
where P. lanceolata is a very common weed of old ﬁelds,
hay ﬁelds and roadsides. Recent studies of E. phaeton in
Massachusetts indicate that populations using both host
plant species as oviposition sites may be relatively
common (G. Breed, E. Crone, personal communication;
h t t p : / / w w w. b u t t e r ﬂ i e s o f m a s s a c h u s e t t s . n e t /
Use of these two host plant species for oviposition by
a single E. phaeton population may have important
consequences for those populations. For example, in
the two populations we studied, there is likely to be
strong selection against oviposition on P. lanceolata:
haying operations destroyed all egg masses we detected
on P. lanceolata. The P. lanceolata plants we observed
occurred almost exclusively in hayﬁelds and these ﬁelds
may be cut two or more times in a single summer,
depending on grass growth. Early season (i.e., June)
haying kills post-diapause late instar larvae and pupae,
when Plantago is a common food plant; while later
season haying could kill adults, egg masses, and
prediapause larvae. Because the native host plant, C.
glabra, often occurs near farm ﬁelds, use of this non-
native, alternative oviposition host by checkerspots may
VOLUME 67, NUMBER 4
be relatively common. There may be other effects on E.
phaeton populations as well. For example, specialist
parasitoids such as Cotesia euphydryidis (Muesebeck)
(Braconidae) and Benjaminia euphydryadis Vierick
(Ichneumonidae) often search for hosts on larval webs
of E. phaeton (Stamp 1982). These webs may be much
less conspicuous when they occur on P. lanceolata
because of the low stature of this species compared to
C. glabra, making them more difﬁcult for parasitoids to
ﬁnd. Thus larvae from egg masses on P. lanceolata may
better escape parasitoids. Furthermore, larval feeding
on these two different host plant species may also affect
palatability of both larvae and adults. When reared on P.
lanceolata, larvae and adults contain two iridoid
glycosides, aucubin and catalpol, whereas those reared
on C. glabra contain almost exclusively catalpol (Bowers
et al. 1992). Feeding experiments with birds showed
that the C. glabra-reared individuals are much less
palatable than those reared on P. lanceolata (Bowers
1980); thus use of P. lanceolata may affect this important
chemical defense in this species.
In conclusion, use of both the native C. glabra and
the introduced P. lanceolata in individual populations of
E. phaeton may have important consequences for these
insects. As wetlands where C. glabra is found become
less common and agriculture and disturbance become
more common, use of P. lanceolata may increase in this
butterﬂy, with multiple and potentially long-term effects
on its populations.
Thanks to E. Crone and G. Breed for their observations on
Massachusetts E. phaeton populations.
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M. DEANE BOWERS (corresponding author;
firstname.lastname@example.org), Museum of Natural
History and Department of Ecology and Evolutionary
Biology, UCB 334, University of Colorado, Boulder
Colorado 80309, USA; LEIF L. RICHARDSON,
Department of Biology, Dartmouth College, Hanover,
NH 03755, USA
Submitted for publication 5 February 2013; revised and
accepted 3 May 2013.
. Egg masses from the Clark site (East Montpelier
County, Vermont). A) Egg mass on C. glabra from this site; B)
egg mass on P. lanceolata from this site. Photographs taken on
July 11, 2011.
FIG.2. Egg masses from the Connor site (East Montpelier
County, Vermont). A) egg mass on C. glabra from this site; B)
egg mass on P. lanceolata from this site. Photographs taken on
July 18, 2011.
3JOURNAL OF THE LEPIDOPTERISTS’ SOCIETY