Complex sentence: After locating the "M. schnecki" nest, the wasp enters only the nests with "P. rebeli" caterpillars and marks the individuals most likely to survive by ovipositing in them.
Split into simpler sentences: After locating the "M. schnecki" nest, the wasp enters only the nests with "P. rebeli" caterpillars. Once she reaches the caterpillars, she marks the individuals most likely to survive by ovipositing in them.