  In this work, we consider a finitely determined map germ $f$ from
$(\mathbb{C}^2,0)$ to $(\mathbb{C}^3,0)$. We characterize the Whitney
equisingularity of an unfolding $F=(f_t,t)$ of $f$ through the constancy of a
single invariant in the source. Namely, the Milnor number of the curve
$W_t(f)=D(f_t)\cup f_t^{-1}(\gamma)$, where $D(f)$ denotes the double point
curve of $f_t$. This gives an answer to a question by Ruas in 1994.
