To multiply \( 4 \) by \( -\frac{5}{8} \), you can first express \( 4 \) as a fraction:
\[ 4 = \frac{4}{1} \]
Now, multiply the two fractions:
\[ \frac{4}{1} \times -\frac{5}{8} = \frac{4 \times -5}{1 \times 8} = \frac{-20}{8} \]
Next, simplify the fraction \( \frac{-20}{8} \):
\[ \frac{-20 \div 4}{8 \div 4} = \frac{-5}{2} \]
Now, to convert \( \frac{-5}{2} \) into a mixed number, we can express it as:
\[ -2 \frac{1}{2} \]
Thus, the final answer as a mixed number in simplest form is:
\[ \boxed{-2\frac{1}{2}} \]