Population ecology of the commensal chironomid Epoicocladius flavens on its mayfly host Ephemera danica

摘要: SUMMARY. 1. Epoicocladius flavens (Diptera: Chironomidae) has a 1-year life cycle in the River Tud eastern England. Pupation and adult emergence occurred from end of May until beginning September. Larval growth was rapid during summer but thereafter almost ceased following April.1 Unlike other chironomids, population density E. very stable remained at around 1000m −2 all through year. 2. Ephemera danica (Ephemeroptera: Ephemeridae), host flavens, 2-year cycle. The proportion infested about 90% for older year-class less than 30% younger autumn summer. A increase infestation as result hatching eggs. Of those infested, hosts harboured two or three larvae, on average, whereas ones had only one. 3. When year-classes were treated separately, frequency distribution number per each month did not depart significantly Poisson distribution. Younger instars departed more frequently instars. 4. majority larvae attached to gills their hosts. As progressed, increasing proportions found thorax, legs tails. thorax preferred site fourth instar larvae. 5. Enhanced chance survival, rather supply detrital food particles which collect host's body, is considered an important benefit accrue this commensalism.