A study of natural populations of the celery leaf-minerPhilophylla heraclei L. (Diptera,Tephritidae)

The study of the population dynamics of the celery leaf-miner, Philophylla heraclei, must take into account the fact that the host-plant is not present permanently and that it develops between the two annual generations of the insect. This development affects in particular the quality and quantity of the leaves fed upon by the mining larvae. It is possible to know the numerical change of the populations from one annual generation to the next (bivoltine insect) and from one year to the next by counting the populations in the various larval instars, responsible for the injury caused to celery. An accurate method of counting of larval numbers, taking into account their change parallel with that of the host-plant, is described in this text. It makes it possible to know with accuracy the duration and importance of the infestations in relation to external factors and to factors inherent to the host-plant itself. Certain traits of larval behaviour, particularly the transfer of a larva from its original mine to a secondary mine as a result of food shortage can thus be established and estimated quantitatively.