Pale yellow dune moth (Copablepharon grandis) COSEWIC assessment and status report: chapter 6

Biology

The biology of Copablepharon grandis is poorly known. This nocturnal moth with a short summer flight season is only rarely observed in the field. Indeed, other than occurring in light-trap captures, it was not observed in the field during the 2004–2005 sampling program. Current knowledge of its biology is based on published information in Lafontaine (2004), Fauske (1992), Seamans (1925), and Strickland (1920).

Lifecycle and reproduction

Based on all records, the flight season of C. grandisis from early May to early October (22 weeks) and peaks around the end of July (Figure 7). In Canada, the flight season is shorter--from early July to late August (8 weeks). Sex ratios in collections are generally evenly split.

Eggs are fully formed in newly emerged adult females, but mating and egg laying have not been observed. Eggs are believed to be deposited in loose, sandy soil (Strickland, 1920). Based on observations in the related Copablepharon longipenne Grote, eggs hatch approximately three weeks later.

Figure 7.  Flight season of C. grandis based on sampling records. The light bars indicate all North American records while the dark bars indicate Canadian records.

Figure 7.  Flight season of C. grandis based on sampling records. The light bars indicate all North American records while the dark bars indicate Canadian records.  

Larval and pupal life stages have not been described except for Strickland’s (1920) observations of one fourth-instar larva purported to be of this species found in early May in a stubble field at Monarch, Alberta. Larvae are believed to feed nocturnally and spend the day buried in the sand; they may also feed on below-ground roots and shoots. Larval growth likely occurs between hatching in August and the onset of cool weather in October. Larvae may undergo a below-ground diapause between the fall and early spring, although the location and depth of burial are unknown. Spring or early summer feeding may also occur prior to pupation (observed in Copablepharon fuscum Troubr & Crabo). The pupal stage is very poorly known except that it likely begins in late June or early July in Canada (July 5 for Strickland’s captured specimen). Pupation occurs in an “earthen cell” below ground (Strickland, 1920).

Copablepharon grandis adults have been observed resting inside Nuttall's evening-primrose (Oenothera nuttallii Sweet) blossoms during the day (C. Schmidt, pers. comm.).

Predation and parasitism

There is no information on predation, parasitism, disease or other factors that may reduce survival of C. grandis. Songbirds were observed feeding on adult C. longipenne moths in the Great Sand Hills and Burstall Dunes in July 2004 (COSEWIC, 2007b) and may also consume C. grandis.

Physiology

Copablepharon grandis flies during the onset of warmer weather in early summer and maximizes its larval growth during July and September. The larvae overwinter in the sand, although conditions of dormancy (e.g., depth of burial) or other overwintering strategies are unknown. It is unknown how seasonal temperature changes affect adult flight periods, mating, or survival of larvae.

The influence of climate on C. grandis distribution is not known. Because the species is at the northern periphery of its range in Canada, climate factors may limit its distribution. Soil freezing or soil moisture levels may be important factors influencing physiology. The lack of captures from the dune systems in the southern Canadian prairies may also be related to climatic factors.

Climate data from the Canadian range in which C. grandis is found are summarized as follows. In Saskatoon, SK, the mean winter (Dec–Feb) temperature is -14.8 °C, the mean summer (June–Aug) temperature is 15.7 °C, the mean monthly winter precipitation is 13.8 mm (95% as snow), and the mean monthly summer precipitation is 47.7 mm. In Wainwright, AB, the mean winter temperature is -14.3 °C, the mean summer temperature is 16.2 °C, the mean monthly winter precipitation is 21.5 mm (97% as snow) and the mean monthly summer precipitation is 61.7 mm.

Dispersal and migration

The dispersal abilities of C. grandis have not been measured. Copablepharon species that have been observed in the field (C. fuscum and C. longipenne) are strong fliers (COSEWIC, 2003; COSEWIC, 2007a). Given that dune habitats are often patchily distributed across the landscape (100 m to 2 km apart), it is likely that dispersal occurs at this scale at least infrequently. However, dispersal between regionally isolated dunes systems (>10 km) is considered unlikely or very infrequent. The potential for long-distance dispersal has likely declined as agricultural activity has developed the landscape between sandy habitats. There is no information that suggests C. grandis migrates.

Interspecific interactions

There is no information on nutrition or interspecific interactions. Strickland (1920) successfully raised an older larva on alfalfa and barley. Copablepharon grandis was often captured (3 of 4 captures) with C. viridisparsa Dod in the 2004–2005 sampling program, but it is unknown whether there is any competition between the species.

Adaptability

There is no information on the adaptability of C. grandis, other than the lifecycle observations and habitat requirements described previously.

A larva reportedly of Copablepharon grandis was raised successfully from the fourth-instar to a pupa by Strickland (1920) using alfalfa and barley as food sources in the laboratory.

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