How do you tell a male boxelder bug from a female?

Body parts, shape and size distinguish the female boxelder bug from the male.

Specifically, reproductive parts are located on the bug in question's (Boisea trivittata) last, rear, third main body part, the abdomen. They facilitate rear-to-rear mating between the two genders. The female is slightly bigger than the male because of an abdomen that can be seen peeping out from under the bug's wings when viewed from above. The female also shows a duller orange color and a more rounded rear.