Stopping rule of host search by the parasitoid, Chrysocharis pentheus (Hymenoptera: Eulophidae), in host patches

Summary We studied the stopping rule obeyed by the female parasitoid, Chrysocharis pentheus , in deciding when to leave the leaflet on which she is searching for larvae of Phytomyza ranunculi . She seemed not to employ some stopping rules that have been suggested; i.e., a fixed‐number rule and a fixed‐time rule and others. The stopping model formulated for Dapsilarthra rufiventris parasitic on the same host species fitted well to the results. The model assumes that the searching female will deposit a marking pheromone on the leaflet at a rate proportional to the search speed and will leave the leaflet when the amount of the pheromone that has accumulated on the leaflet reaches the threshold, L. In this model, L denotes the amount of search effort spent on the leaflet. A comparison of the observed results with the predictions from the model suggested that L increased markedly at the first encounter with the mine (host), but less at later encounters. C. pentheus appears to employ a mixed strategy of a fixed search‐effort and an area‐concentrated search. This would confer an adaptive advantage in foraging for P. ranunculi larvae, which are distributed in clumps among leaflets in the field.