When you line up 10 box elder beetles and 10 pill bugs in neat rows, the pill bugs take up slightly more space. You can picture the pill bugs forming a group 2.81 in (7.12 cm) wide, while the box elder beetles form a group 2.43 in (6.17 cm) wide.

How much space each takes up
10 pill bugs lined up in neat rows is about 1.15 times the size of 10 box elder beetles lined up in neat rows.
Typical adult or standard sizes; real ones vary.