Abstract
The present paper studies how a parasite, Kratochviliana sp., of the Ranunculus leaf mining fly searches and attacks its host larvae. When the parasite alights on a Ranunculus leaf, it walks about rather directly until it encounters a mine formed by the host larva. It then searches ingeniously for its host along the mine using its antennae. Simulation models revealed that this characteristic host searching procedure is adaptive for lacating leaf mining insects. The parasite seemed to recognize the host and to receive stimuli for inserting its ovipositor into the host from the somewhat swollen surface which the host larva pushes up within the mine. The parasite, after finding the host, often inserted its ovipositor into the host body through the epidermis of the leaf. Sometimesm however, it left the host without ovipositor insertion after roaming over it, or passed it without any reaction. When insertion occurred, the parasite laid an egg in the host or fed on its body fluid after killing the host by injecting venom into its body. In some cases, however, it did not kill the host even when inserting its ovipositor. No eggs were laid in a dead host though the parasite sometimes fed on the host. The parasite attacks mainly the second and the third-instar larvae. On the average a parasite killed 182.3 hosts and laid an egg in each of 103.4 of them during its life span of 22.8 days.
