MUTUAL USE OF LEAF-SHELTERS BY LEPIDOPTERAN LARVAE ON PAPER BIRCH

1. Many species of birch-feeding Lepidoptera make leaf-shelters by tying leaves together with silk. Several species, or several instars of a single species, may be found together within a single leaf-shelter. 2. Shelters made in June by the birch tube-maker Acrobasis betulella (Pyralidae) are colonized throughout the season by other Lepidoptera. Artificial A.betulella shelters, made by tying leaves together with string, were colonized at a greater rate than nearby control foliage, indicating that secondary species are indeed responding to the presence of the shelter, and not to some other aspect of plant quality. 3. Several species in the families Oecophoridae, Gelichiidae and Stenomidae make 'leaf-sandwiches' by tying two leaves together; these are later colonized by oviposition from adult A.betulella. Artificial sandwiches made by joining leaves together with paperclips were colonized by several species of sandwich-makers, as well as by A.betulella. Colonization occurred mainly via oviposition, although some sandwiches may have been colonized by wandering larvae. 4. First instar A.betulella, which cannot form their own shelter, enjoyed greater survivorship when placed in artificial leaf-sandwiches than when placed on leaves without sandwiches.