The following paragraph is taken from the "Catholic Almanac"

James the Less: Son of Alphaeus, called "Less" because he was younger in age or shorter in stature than James the Greater; one of the Catholic Epistles bears his name; was stoned to death in 62 or thrown from the top of the temple in Jerusalem and clubbed to death in 66; in art, is depicted with a club or heavy staff; May 3 (Roman Rite), Oct 9 (Byzantine Rite).

James the Less feast day is celebrated with St Philip on May 3rd. This James is called James, Son of Alphaeus. According to Fr Foley, O.F.M. who I have quoted previously, we know nothing of this saint but his name, and of course the fact that Jesus chose him to be one of the twelve pillars of the New Israel, His Church. He is not the James of Acts, son of Clopas, "brother" of Jesus and later bishop of Jerusalem and the traditional author of the Epistle of James.

http://www.12apostlesofthecatholicchurch.com/

James the Lesser:  Named as such because James the Greater became an Apostle before him