English: Oviposition behavior of a female Trichogramma wasp into a Pieris brassicae egg. Eggs of the large cabbage white butterfly P. brassicae are normally present within a clutch of 20–50 eggs. For a better view the butterfly egg was isolated from the clutch. After the first contact a female wasp walks over - and drums with her antennae on - the butterfly egg to assess its size [32]. She then carefully adjusts the number and sex of the eggs that she oviposits into the butterfly egg accordingly [45]–[48]. After oviposition, the wasp eggs will develop into adult wasps inside the butterfly eggs at the cost of caterpillar development. Movie (41 seconds) courtesy of Nina E. Fatouros, Martinus E. Huigens and Urs Wyss (Institute of Phytopathology, University of Kiel, Germany).