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.