ECOLOGY OF CASE-BEARING MOTHS (LEPIDOPTERA, COLEOPHORIDAE) IN A NEW-ENGLAND SALT-MARSH

The natural history, oviposition, feeding behavior, and parasitism of Coleophora caespititiella Zeller and C. cratipennella Clemens in a Rhode Island salt marsh are described. C. cratipennella is univoltine and feeds only on the rush Juncus gerardi Loisel. C. caespititiella is bivoltine; the spring generation larvae feed on J. gerardi and the fall generation larvae feed on the annual Salicornia europaea L. This is the first report of bivoltinism in this genus and the first report of a single Coleophora species feeding on plants in these two plant families. In J. gerardi monocultures, oviposition frequency increased with increasing flowering culm density and flower density per culm. In S. europaea monocultures, oviposition frequency initially increased with plant density, but moths appear to be satiated by high-density S. europaea stands. Overall, larvae infested 22% of the J. gerardi seed capsules and reduced seed set in these infested capsules by 60%. C. caespititiella larvae consumed from 4 to 25% of the seeds of S. europaea. Larvae were rarely seen to move from the flowering culm or plant where they were first encountered. Eighteen percent of C. cratipennella larvae and 10% of first-generation C. caespititiella larvae were parasitized by an unidentified ichneumonid wasp. Because these moths feed on two plant species with known asymmetric competitive interactions and consume more seeds of the dominant competitor (J. gerardi), the moths may mediate the competitive interactions between J. gerardi and S. europaea.