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Sand-verbena Moth (Copablepharon Fuscum)

Biology

General

The biology of Copablepharon fuscum is poorly understood. No detailed studies have been undertaken since the species was described in 1995. This summary is based on published sources (Troubridge and Crabo, 1996; Tatum, 2002), observations made during sampling and inferences from general moth biology.

Adults have been observed or captured during dusk and early night between May 19 and July 1 on or near flowering A. latifolia plants. The flight season is estimated to be approximately 45 to 55 days and appears to peak around June 10, based on the midpoint between the earliest and latest recorded capture date. Adults may live between 5 to 14 days (J.T. Troubridge pers. comm., 2002). The moth has one flight season per year.

Adults have been observed intently nectaring on A. latifolia flowers. C. fuscum has a long proboscis that allows it to access nectar within the trumpet-shaped flower of A. latifolia. Mating has not been observed. Observations indicate that eggs are laid singly or in groups on the composite inflorescence of A. latifolia or on adjacent leaves (Troubridge and Crabo, 1996). Larvae hatch after approximately 2 weeks and feed on the leaves of A. latifolia. Feeding initially focuses on leaf-mining within the leaf epidermis and subsequently on the exterior of the leaves as the larvae mature. Feeding was not observed during the day and is believed to be exclusively nocturnal (Troubridge and Crabo, 1996). Larval feeding and growth slows with declining ambient temperature, and larvae remain dormant during the winter in the sand below A. latifolia patches. Larvae that were captured and raised artificially emerged to feed on new flower buds in late April and early May (J. Tatum, pers. comm., 2002). Pupation appears to occur in late April to the end of May and lasts approximately 10 days.


Reproduction

Very little is known about the reproduction of this species including mating behaviour (e.g., pheromones, mate selection, etc.). Reproduction occurs once per year. Mating commences as early as May 15, peaks around June 10 and finishes by late June. Eggs are deposited singly or in small groups on the inflorescence or leaves of A. latifolia (J.T. Troubridge pers. comm., 2002). Sex ratios in collections are generally evenly split (J.T. Troubridge pers. comm., 2002).


Survival

Annual and longer-term survival rates are unknown. There is no information on predation, intra- or inter-specific competition, stochastic effects such as climate or disturbance, disease or other factors that may reduce survival of C. fuscum.


Physiology

C. fuscum flies during the onset of warmer weather in late spring and maximizes its larval growth during July and August. The larvae overwinter in the sand, although conditions of dormancy (e.g., depth of burial) or other overwintering strategies are unknown. Larvae may use warmer periods during the fall and spring to feed briefly on A. latifolia leaves (J. Tatum pers. comm., 2002). It is unknown how seasonal temperature changes affect adult flight periods, mating or larvae survival. In June 2002, adults were captured during unseasonably cool, windy weather at two sites in Puget Sound.

Climate may be an important limiting factor for C. fuscum distribution. No occurrences have been recorded on the west coast of Vancouver Island despite the presence of A. latifolia in dunes and beaches. The west coast of Vancouver Island has a hypermaritime climate with slightly cooler summer and substantially higher winter precipitation compared to the southeast side (Phillips, 1990). It is not known how these differences affect the distribution of C. fuscum. Other Copablepharon species are restricted to arid regions.


Movements/Dispersal

Dispersal abilities of C. fuscum have not been assessed and are difficult to infer from other species. Three points are important when assessing the potential dispersal abilities of C. fuscum:

  1. Observations and trap records by N. Page made in 2002 indicate that C. fuscum is rarely found away from dense patches of flowering A. latifolia plants. Traps sited more than 25 m away from patches have not captured individuals.

  2. In contrast, C. fuscum appears to be a strong flier. Moths disturbed during nectaring were often able to evade capture by hand net through rapid flight. Moths also flew strongly in winds between 5 and 15 km/hour. Noctuid moths are generally good dispersers, and a mark-recapture study in Finland found dispersal distance as high as 30 km, although average distances were around 100 m (Nieminen, 1996).

  3. Satellite patches of A. latifolia located away from the central patch also supported C. fuscum at some sites. Based on observations of isolated, small A. latifolia patches, these satellite patches are unlikely to support C. fuscum over the long term. Population persistence is therefore likely maintained by colonists from the central patch.

In summary, recolonization of Canadian populations from known US populations is unlikely. The closest known population to the southern Canadian sites is 33 km away over water. However, many noctuids are good dispersers, and more detailed information is required to assess recolonization ability.


Nutrition and Interspecific Interactions

C. fuscum relies on A. latifolia for adult and larval nutrition. The relationship is considered a parasite/host association.

A. latifolia has dense, sticky, glandular trichomes on the leaves and stems that may serve to reduce herbivory by insects. The chemical defenses of A. latifolia and specific adaptations of C. fuscum to avoid their effects are unknown.

There is no indication that C. fuscum is able to use alternate host-plants. Most dunes support a small group of distinctive plant species (e.g., Glehnia littoralis spp. leiocarpa, Carex macrocephala, Convolvulus soldanella, Poa macrantha, Polygonum paronychia) that are not similar to A. latifolia in terms of flower or leaf structure. Captive raised larvae rejected other plant material, and fresh A. latifolia leaves and stems were required for successful rearing (J. Tatum pers. comm., 2002).


Behaviour/Adaptability

Behaviour, other than the lifecycle observations described previously, is unknown.

Some monophagous insects are able to change host-plants, often to related species (Young, 1997). However, there is no indication that C. fuscum has diversified to use other host-plants for adult nectaring or larval feeding. As well, there are no plant species closely related to A. latifolia in the Georgia Basin / Puget Sound region.

C. fuscum appears to be tolerant of direct human activities. Adult moths were captured near low-use roads at several sites.

C. fuscum was raised successfully from young larvae to adults (J. Tatum pers. comm., 2002). Rearing required frequent addition of new A. latifolia leaves for feeding. No C. fuscum population transplants have been attempted but would likely be successful if adequate host-plant resources were provided.