The holly leaf miner as a study organism

The dipteran Phytomyza ilicis (the holly leaf miner) is a useful subject fo r practical work aimed at teaching life cycles, mortality factors, and popu lation dynamics. It is found widely throughout most of Britain and its dens ity varies both regionally and locally. It has a simple life history, in wh ich eggs are laid in June on new holly leaves, larvae form mines in late su mmer onwards, pupate in early spring, and adults emerge in May and June. Mo rtality factors, such as parasitism and bird predation, operate at differen t stages of the holly leaf miner's life cycle, and their relative impacts c an be assessed from single collections of mined leaves harvested from July through to November, after the insect's life cycle is completed. The holly leaf miner system has provided Open University students, studying the Scien ce Foundation Course throughout Britain, with practical experience of study ing living organisms in the field. Students examined a sample of mines and calculated the relative magnitudes of different fates. The frequency and ty pe of error which students made in scoring the fates of the miners were qua ntified. The lessons learnt from the use of the holly leaf miner system as a subject for practical work are reported.