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Tachinidae (parasitic flies; order Diptera, suborder Cyclorrapha) Large family of true flies whose larvae are parasites of insects and other arthropods. The adults are distinguished by a strong fan of hypopleural bristles, and a well-developed postscutellum. The second abdominal sternite is visible as side plates lying above the tergite. The larvae are unlike other cyclorraphan larvae in being uniformly cylindrical, rather than tapered. There are many larval habits and methods for attacking hosts: (a) eggs are laid on the surface of the host; (b) eggs are laid in large numbers on potential food plants for the host, and are eaten; (c) eggs are laid near the habitat of the host, and hatch into active larvae which seek out a host; and (d) larviparous females puncture the skin of the host and deposit an egg which hatches immediately. The usual hosts are larval or adult Coleoptera, Orthoptera, and Hemiptera, occasionally Hymenoptera, but most frequently Lepidoptera. The larvae breathe either by maintaining a connection with the air outside the host, or by tapping the air supply of the host at a tracheal trunk. More than 9000 species have been described, and their distribution is world-wide.