Life histories of four species of limnephilid caddisflies in a pond in southern Alberta
The life histories of four species of limnephilid caddisflies in a permanent pond in southern Alberta were investigated. Nemotaulius hostilis overwinters in the larval stage and displayed other life history traits restricting it to life in permanent aquatic habitats. Limnephilus externus and Anabolia bimaculata overwinter out of water in desiccation-resistant egg masses as first instar larvae and so can also survive in temporary pool habitats. Glyphopsyche irrorata is primarily a permanent pool resident but can survive winter drought conditions because it overwinters in the adult stage. Incubation experiments showed that L. externus eggs, which are deposited on the ground in autumn, are adapted to developing over a wide range of temperatures and at cooler temperatures than are the eggs of~ hostilis, which oviposits on riparian vegetation in mid-summer. L. externus eggs developed in both water and air whereas N. hostilis eggs developed only when out of water. SEM studies of the structure of the polysaccharide matrix of the gelatinous egg masses of five species of caddisflies and a snail revealed a relationship between structure and desiccation-resistance. The results of the SEM study indicated that egg mass structure may provide information of taxonomic and phylogenetic importance concerning the Trichoptera. All four species studied are shredders. The two species capable of surviving in temporary pool habitats (h externus and A. bimaculata) displayed the highest larval growth rates of the four species studied. Laboratory experiments indicated that caddisfly larval feeding preferences are a combination of preferences for food and case-building materials. The patterns of emergence, maturation, mating and ovi position indicated that adult G. irrorata and A. bimaculata did not undergo a reproductive developmental delay whereas adults of both sexes of L. externus and N. hostilis did. The evolution of life history traits (including oviposition out of water) enabling limnephilid caddisflies to survive in temporary pool habitats is viewed in terms of the Thermal Equilibrium Hypothesis. The widespread occurrence of adult reproductive developmental delays in this family is seen as an adaptation enabling animals to avoid the high, metabolically-costly water temperatures of mid-summer. Adult reproductive delays and oviposition out of water may thus have preadapted members of the Limnephilidae to exploiting temporary aquatic habitats.
Bibliography: p. 231-239.
Berte, S. B. (1981). Life histories of four species of limnephilid caddisflies in a pond in southern Alberta (Unpublished doctoral thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/18255