Aspects of the ecology of the moth Coleophora alticolella have been investigated at a low-altitude site on the Cumbrian coast (15m above sea-level) and along a transect from 215m to 610m on the western escarpment of the northern Pennines. The larvae of this moth feed on the seeds of the rush Juncus sguarrosus. Seed production by the food-plant is reduced at higher altitudes, where the climate is severe. The oviposition period is delayed with increasing altitude and the eggs are laid singly, if there are sufficient oviposition sites on the developing inflorescences. Survival of the larvae, between hatching and establishment inside the food supply, is directly related to the proportion of J. squarrosus florets developing into seed capsules. Consequently, as a result of the progressive reduction in seed capsule production with increasing altitude, there is greater mortality during larval establishment at the higher sites. Larval case production and subsequent migration to overwinter in the leaf- litter are both retarded with increasing altitude, provided that the food supply is adequate. Both the number of species of parasitic Hyraenoptera, attacking the larvae, and the percentage parasitization are reduced with increasing altitude. .Hyperparasitoids were present at the lowest site. Starvation of the larvae, as a result of the reduced J. sguarrosus seed production, was the most important mortality factor in the population dynamics of Coleophora alticolella at the highest altitudes. Parasitoids controlled the population at the lowest altitude. Between these two extremes, competition for food by the fourth instar larvae is most important. This acts as a density-dependent factor, reducing natality in the following spring. The larvae often eat all of the seeds produced by the food-plant in this middle region, but not at sites of higher or lower altitude.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:575755 |
| Date | January 1980 |
| Creators | Randall, Martin G. M. |
| Publisher | Durham University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.dur.ac.uk/7424/ |
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