Sentence:  "Parasites and <WSD>Hyperparasites</WSD>".— [...] How the Pteromalus contrived to introduce its eggs into the Tetrastichus, and how the Tetrastichus managed to oust the Microgaster must for the present remain open questions for the consideration of the learned. 
Meaning of the word marked with <WSD> tags:  An insect that parasitizes another parasitic insect.