This fly inflates its head

The inflation is done by pumping hemolymph into the head; the maneuver is necessary because the fly uses head inflation to break the walls of the chamber in which it hatched from its larval form: "Newly-eclosed flies use their head blister (ptilinum) to exert hydraulic pressure on particles of the cell partitions and produce small holes."

Details at Physiological Entomology, via New Scientist and Not Exactly Rocket Science.