In 1904, four High-Seas Torpedo Boats were laid down at the Pattison shipyard of Naples, to a design licensed from the British shipbuilder Thornycroft.

[2][3] They were powered by two triple expansion steam engines fed by two Thornycroft coal-fired water-tube boilers which gave 2,900–3,279 ihp (2,163–2,445 kW) driving two shafts and allowing the contract speed of 25 knots (46 km/h; 29 mph) to be reached.

Actions involving the Pegaso class included Cigno carrying out shore bombardment along with larger units of the fleet in support of Italian land forces near Tripoli in November 1911,[7] and a reconnaissance of the Dardanelles by five torpedo boats (the Sirio-class ship Spica and four Pegaso-class ships, Perseo, Astore, Climene and Centauro).

[2] Arpia struck the wreck of the Neapolitan frigate Torquato Tasso (which had sunk off Porto d'Ascoli in 1861) on 17 January 1918.

It sustained major damage and sank in shallow water, but was raised and repaired, re-entering service in July 1918.