Any of various stout, two - winged flies, chiefly of the genera Gasterophilus and Oestrus , having larvae that are parasitic on various animals, especially horses and sheep, and sometimes on humans.

• 雌性动物的)动情,动情周期:大多数哺乳动物(包括人类)的雌性产生的周期性的性冲动,在此期间内雌性具有排卵的优势,所以该期间最适合性交;