"Males have to grow these outrageously large testes and the sperm are all rolled up inside," Pitnick explains. "The testes are about 11 percent of the male's total body mass."
Fun fact: fruit Flys are sexed (both in the sense of determining their biological sense, and the act of fornication) by "sex combs". The forearms of the males have little "combs" (absent in females) that the males use to shove a big ol ball of sperm into the female.
You are welcome for this unasked bit of knowledge.