THE INTERTIDAL CHIRONOMIDAE (DIPTERA) OF BRITISH COLUMBIA: II. LIFE HISTORY AND POPULATION DYNAMICS

Publisher Website
Google Scholar
Abstract
Intertidal Chironomidae (Diptera) are represented on the coast of British Columbia by Paraclunio alaskensis Coquillett and Saunderia pacificus (Saunders), S. marinus (Saunders), and S. clavicornis (Saunders). These species inhabit a variety of rocky shore types, being found on exposed as well as protected shores, but are not present on exclusively sandy shores. Their range extends at least to the Queen Charlotte Islands, the most northerly area collected during this study. S. clavicornis is the most ubiquitous of the four species while S. pacificus is the rarest.Within their habitat larval distribution is contagious and is well described by the negative binomial distribution. It is probable that their clumped distribution is due to environmental factors rather than active aggregation. Larval densities of 4316/ft2 were recorded for Saunderia spp. and 1613/ft2 for P. alaskensis. Larvae fed on green algae and diatoms and it was demonstrated that they can select certain groups of diatoms from the substrate.Adult emergence occurs throughout the year but is most intensive in the fall and least in the late spring and summer. Generally, larval population fluctuations follow adult emergence trends. It is hypothesized that larval population fluctuations are caused by a combination of overlapping multiple generations and differential larval growth rates at fluctuating temperatures, coupled with varying lethal environmental factors at different times of the year. Developmental times at 10 °C from egg-laying to adult emergence was 110 days for S. clavicornis, 150 days for S. marinus, and 204 days for P. alaskensis.