Sand-verbena Moth Surprise

It has been too long since I’ve checked out the plants in the spectacular dunes at Goose Spit. A number of specialized plants grow in these dunesyellow sand verbena (Abronia latifolia) and black knotweed (Polygonum paronychia) are prolific. With a little effort, other interesting plants can be found as well.

Black Knotweed (Polygonum paronychia)
A large patch of Black Knotweed (Polygonum paronychia) just above the drift logs at Goose Spit, Comox, BC.

My intention was to photograph the yellow sand-verbena. Large mats of the low, sand loving plant grow in the foreshore dunes along the main access road and parking areas, but the better patches are further along the spit. Given the time of day (early evening), I thought that there might be an outside chance to find sand-verbena moth (Copablepharon fuscum) as well. I knew that this very rare, red-listed moth is found only in association with its host plant, the yellow sand-verbena. The sand dunes at Goose Spit are one of only 10 known locations where this moth has been found along the shores of the Salish Sea.

Yellow Sand-verbena (Abronia latifolia)
Yellow Sand-verbena (Abronia latifolia) grows relatively abundantly in the dunes at Goose Spit, Comox, BC.

After a couple of hours the light was beginning to fail and the wind was picking up making flower photography particularly challenging. It was then that I noticed a small, pale moth nectaring on the flower of a yellow sand verbena—I couldn’t believe my luck, a sand-verbena moth!

Sand-verbena Moth (Copablepharon fuscum)
The red listed Sand-verbena Moth (Copablepharon fuscum) is found only in association with yellow sand-verbena.

The connection between the moth and yellow sand-verbena is very strong. The moth depends exclusively on the sand-verbena in all stages of its life-cycle except for when it is pupating. Adults live a brief one to three weeks. During this time (typically May/June, with a peak in mid-June that coincides with the flowering of the yellow sand-verbena) the adults nectar on the flowers of the sand-verbena, mate, and lay eggs. The eggs hatch in approximately two weeks and the larva feed at night on the flowers and leaves of the sand-verbena for the rest of the summer. Rather than overwintering as pupae, the larva enter a period of dormancy called diapause in the early fall. They awaken in the early spring and continue to feed on leaves in preparation for pupation. Pupation occurs in April and May and takes place underground in the sand.

Sand-verbena Moth (Copablepharon fuscum)
The Sand-verbena Moth (Copablepharon fuscum) blends in well with the sand and dried up brown vegetation in the dunes.

The sand-verbena moth is extremely well suited to its habitat and blends in well with the sand and dried brown vegetation. If I hadn’t initially seen the moth in the open on the flower, it would have been extremely difficult to find it nestled close to the sand on the leaves of the sand-verbena. I watched as it flew from the flower and disappeared at the base of one of the plants a short distance away. Once it had landed in a protected, less-visible location, it was very cooperative, not moving much as I spent a short time photographing it.

Yellow Sand-verbena (Abronia latifolia)
The Yellow Sand-verbena (Abronia latifolia) is the host plant of the red-listed Sand-verbena moth.

As a red-listed species, the future of the sand-verbena moth is precarious. It depends on a single host plant (yellow sand-verbena) which grows in a specific habitat. Coastal dune ecosystems on Vancouver Island are vulnerable to habitat degradation due to human recreation and development, rising sea levels associated with climate change, displacement of sand-verbena by invasive introduced species, and the use of insecticides and herbicides that inadvertently may kill the moth. In British Columbia it has been reported in only three locations—Goose Spit, Sandy Island (near Denman Island), and three associated sites near Sidney, Saanich Peninsula. The total area of the 5 sites is around 15 hectares. It is also found along the shores of Puget Sound in Washington.

The dunes at Goose Spit are an extremely interesting and fragile place. Please use care if you decide to visit and minimize your impact. If you’re lucky and time it right, you might just see a sand-verbena moth as well!

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5 comments

  1. Thanks Dave for alerting me to the existence of both the sand verbena and the sand-verbena moth. Have marked it on my nature calendar for a visit next mid-June.

    Looked up the original description (J.Ent. Soc.BC, vol 92, p. 87-90) and was surprised to find that the moth was only described in 1995.I find it amazing that a moth can live undetected for 150 years in a fairly populated area such as the Salish Sea before being discovered! How many other undescribed insects are lurking around in our local native environments?

    Looking forward to your wife’s nature walk at Paradise Meadows next Sunday. As a newcomer to the island, I have a lot to learn about the local natural history. With the current low tides, I am looking for Midshipman nests under rocks and hopefully hear it croak. It is supposed to be one of the noisiest aquatic animals.

  2. Thanks for dropping in Hans – you might want to try looking for larva in a couple of weeks. I’m hoping to get out with the field crew out here in Pacific Rim National Park in mid July. Hope you enjoyed the walk!

  3. Hello Dave,
    We have just returned from Tree Island (Sandy Island) and noticed a spiky kind of sedge-like plant. (Is it Big Headed Sedge?) We have kayaked to this island for four years and this plant seems to be spreading rapidly. Is it a threat to the Yellow Sand Verbena, and hence, the Yellow Sand Verbena Moth? We didn’t see the moth but did see a swallowtail species.
    Thanks for your help!
    Gail

  4. Hi Gail – big headed sedge does grow on Sandy Island and it is a distinctive species, that’s likely what you saw. It is a native species and not a threat to the yellow sand verbena. It would definitely be cool to get a sand verbena moth record for Sandy Island!

  5. Pingback: Island Nature  :: Lions in the Dunes at Goose Spit

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