Egg case

Definition

A protective enclosure surrounding eggs, produced by various animals. In arthropods, the term most commonly refers to the ootheca—a hardened, foam-like or leathery capsule secreted by female cockroaches (Blattodea), mantids (Mantodea), and some other insects to shield embryos from desiccation, predation, and mechanical damage. Egg cases may be deposited on substrates, carried externally, or retained within the female's body until hatching.

Etymology

From Middle English egge + case, in biological use since at least the 19th century

Example

The German cockroach (Blattella germanica) produces a purse-shaped ootheca that protrudes from her abdomen for several days before she deposits it in a sheltered crevice; the egg case contains 30–40 embryos and resists many insecticides.

Synonyms

• Ootheca

Related Terms

• Ootheca
• Chorion
• egg pod
• Spermatophore
• oviposition
• ovipositor
• embryonic diapause

Usage Notes

Specialists reserve "ootheca" for the specialized foam-hardened cases of cockroaches and mantids, using "egg case" more broadly for any protective egg enclosure, including the leathery "mermaid's purses" of cartilaginous fishes and the silk-wrapped egg sacs of spiders. The distinction matters in identification: cockroach oothecae have a distinctive ridged or segmented appearance and are often key diagnostic evidence in pest management surveys.