Besides monsters, I love finding Mermaids and/or Sirens in embroidery and lace. I can't tell you why and you could even say that the Siren is a type of sea monster.
From Giovanni Ostaus' La Vera Perfezione del Disegno per Punti e Ricami (1561):
They are always wicked in the old tales and it was probably not until Hans Christian Andersen that there was a sympathetic tale of these creatures - don't quote me, I'm not up on my Mermaid/Siren history. The Greeks didn't even associate them with the sea but the Romans did and since we're talking about Italy, let's go with the Romans! You do need to know however that Sirens get some bird-like history from the Greeks so sometimes they are depicted with wings. Enough background – on to the Sirens in needlework!
From Cesare Vecellio's Corona delle nobili e virtuose donne (1592):
Years ago when searching for Italian patterns, I came across the Coraggio Sampler by The Scarlet Letter. This sampler has all kinds of things I like including monsters and a Mermaid. I actually came across a sampler in an Italian museum with the Mermaid from this sampler on it but I didn't note it down and now I'd love to know where I saw it!! Anyone know? Please leave me a comment below!
I like the documentation that goes with the Coraggio Sampler, it has references to 16th century antique pattern books. I ordered it with all the silk threads and then decided to modify it with other antique Italian motifs I liked so it sits on the floor stand in my living room and once in awhile I sit and put in a few stitches on it. I'm afraid it has been sitting there for years.
There are several needle lace Sirens in Merletti e Ricami della Aemilia Ars (1929) including several on a round table centre on the cover which was a piece commissioned "from America", I tried to scan it but unfortunately I can't get a good scan, you'll have to take my word for it...
... there is also this Heraldic design by Arcangelo Passerotti from his Libro di Lavorieri (1591):
In the same book there is this one done in Filet lace for a tablecloth, the design is from Giovanandrea Vavassore's Esemplario di Lavori (c. 1530):
I have always liked the Siren in Elisa Ricci's Old Italian Lace (1913):
I took a crack a charting the design, what do you think? She's pretty scary!
You can download some of Elisa Ricci's books and some antique pattern books from the Online Digital Archive of Documents, or you can purchase a collection of 5 antique pattern books together in one volume from Italian Needlecrafts.