In the Stylopidia, the female's anterior region protrudes out of the host body and the male mates by rupturing the female's brood canal opening, which lies between the head and prothorax. Sperm passes through the opening in a process termed hypodermic insemination. The offspring consume their mother from the inside in a process known as hemocelous viviparity. Each female then produces many thousands of planidium larvae that emerge from the brood opening on the head, which protrudes outside the host body. These larvae have legs and actively search out new hosts. Their legs are partly vestigial in that they lack a trochanter, the leg segment that forms the articulation between the basal coxa and the femur).