Cockroaches release tiny brown, capsule-like egg sacs, or oothecae, that store multiple embryos, according to Orkin. Depending on the species, the ootheca's size ranges from 5 to 10 millimeters. The protein content of the egg sac helps its casing harden to protect the growing embryos.
Each cockroach species produces oothecae with distinct coloring. For example, American cockroach egg sacs are dark brown, while Oriental cockroaches have dark reddish-brown sacs. German cockroaches store large numbers of eggs in a single sac, producing up to 50 embryos at once, Orkin states. Brown-banded cockroaches hatch as few as 10 embryos at a time and produce some of the smallest oothecae, which are typically 5 millimeters in length. Most species produce multiple oothecae in one lifetime.
Many female cockroaches initially carry oothecae attached to the outside of their abdomens, according to HowStuffWorks. Some species drop, bury or hide the sac, leaving the nymphs to fend for themselves when they emerge. Other cockroaches transport the sac until hatching time and nurture their young after birth. Ovoviviparous and viviparous roaches produce live young. In ovoviviparous species, eggs develop inside an internal ootheca, while viviparous species grow in the uterus surrounded by protective fluid. The hatched nymphs are often white at birth and gradually turn brown as their exoskeletons develop.