Answer
The insects require an additional time of $~~\frac{5.0}{v_s}~~$ when they travel the first $2.0~m$ without sailing.
Work Step by Step
In part (a), we found that $~~\frac{v_s}{v_{ns}} = 3.5$
Then: $~~v_{ns} = \frac{v_s}{3.5}$
We can find the time $t_s$ to complete $2.0~m$ with sailing:
$t_s = \frac{2.0}{v_s}$
We can find the time $t_{ns}$ to complete $2.0~m$ without sailing:
$t_{ns} = \frac{2.0}{v_{ns}}$
$t_{ns} = \frac{2.0}{\frac{v_s}{3.5}}$
$t_{ns} = \frac{7.0}{v_s}$
We can find the difference in times:
$\Delta t = \frac{7.0}{v_s} - \frac{2.0}{v_s} = \frac{5.0}{v_s}$
The insects require an additional time of $~~\frac{5.0}{v_s}~~$ when they travel the first $2.0~m$ without sailing.
