Engraulis encrasicolus, also known as alici. People argue endlessly about the difference, but in reality acciughe and alici are the same fish, the former preserved in salt, the latter in oil. Although most anchovies in Italy are preserved in salt (and come from Spain's Atlantic coast), from May to September smaller, more delicate Mediterranean anchovies appear. They play an important role in local cuisines, as in puttanesca sauce.
In the south, fresh or salted, they're in everything. Look for 'white anchovies' (filleted and marinated in white vinegar) or anchovy fillets ground into a paste, an important ingredient in the classic Sicilian pizza, sfincione.
Salted Ligurian anchovies (Engraulis Encrasicolus L) are especially prized, tender and tasty due to the saltiness of the Ligurian sea. Fished at night between April and mid-October using electric or gas lamps to attract them ('della lampara') they are up to 20cm long and are prepared according to a traditional method in glass containers called arbanelle. They are designated IPG.
Image by Chad Kainz