Male and female reproductive anatomy of a “spearer” mantis shrimp, Squilla empusa, is described using light and scanning electron microscopy as well as dissections. The genital region of females is located medially on the sixth thoracic sternite. It consists of a pair of gonopores connected by a medial genital slit, which leads to a cuticlar sperm storage organ that is shed with every molt. Sperm and accessory material have been located in the seminal receptacle. The accessory material appears to serve as a sperm plug. Females have three internally located cement glands that are visible through the exoskeleton on the thoracic sternite surface. The cement-gland material forms a matrix that holds individual embryos together in a uniform mass. Cement glands develop in synchrony with the ovaries, and development is divided into three stages. Posterior to the gonopores is a medial pore from which material from the cement gland is released. Reproductively active females have ovaries that are oriented anteriorly to posteriorly and are visible dorsally and ventrally through the exoskeleton. Males have paired penes that arise from the last pair of walking legs on the eighth thoracic sternite. The distal end of each penis has two openings: 1) one from the vas deferens that transfers sperm and 2) one from the accessory gland duct that contains sperm plug material for the female seminal receptacle. Male penes are not symmetrical; the left penis is significantly longer when compared to the right penis. Under laboratory conditions, most females that did not have immediate access to males before oviposition produced unfertilized eggs. Two females produced fertilized eggs; one lacked contact with a male for four weeks, and one had constant male contact. The seminal receptacle may normally serve as short-term sperm storage, even though long-term storage was documented. Molting is not related to oviposition. Females produce consecutive broods of eggs an average of 40.6 days apart. Based on the location of the oviducts with respect to the female seminal receptacle, fertilization occurs immediately after the eggs are extruded from the oviducts.