What is the difference between the saltarello and the tarantella?
The tarantella and saltarello are traditional Italian dances, both usually notated in a fast compound duple time such as 6/8. The steps are different, but the musical difference isn't so clear. The last movement of Mendelssohn's "Italian" Symphony is called a saltarello. His Song Without Words Opus 102, No.3, is often called a tarantella, though I think the title is by an editor rather than the composer.
La Gazetta Italiana discusses the two dances. It says the saltarello is Roman in origin and apparently was too suggestive for the taste of church officials. The name comes from the Italian verb meaning "jump." The tarantella comes from the Taranto area, and there's a folk legend that dancing it will throw off the effects of a tarantula bite, or perhaps it imitates the spasms suffered by a bite victim.
The saltarello in the Italian Symphony is written in 4/4 time. Triplets dominate the rhythm, but there are parts with non-triplet dotted quarters and eighth notes. As it's usually performed, it's faster than the usual tarantella, but it's unwise to draw conclusions from one sample. Is there a consistent difference in the music associated with the two dances? Is the answer different depending on whether we're looking at classical or folk music?