The structure often mistaken for a praying mantis cocoon is correctly known as an ootheca, which is the specialized egg case produced by the female. Mantids undergo incomplete metamorphosis, meaning their life cycle progresses directly from egg to nymph to adult without a pupal stage. Insects that spin a cocoon, such as moths and butterflies, go through complete metamorphosis, which includes a pupal stage. The ootheca is a protective container designed to house and insulate the developing young through winter.
Identifying the Mantis Ootheca
The ootheca is a highly durable, asymmetrical structure created by the female mantis from a frothy secretion that quickly hardens upon contact with the air. This proteinaceous foam forms a rigid, layered matrix that provides insulation and protection against predators and harsh weather. While visual characteristics vary widely by species, the egg cases often share a foam-like, papery texture.
For instance, the ootheca of the Chinese mantis tends to be roundish and roughly textured, sometimes resembling Styrofoam. These cases can be quite large, measuring several inches in length. Conversely, the native Carolina mantis produces a flatter, teardrop-shaped case that is generally smaller and smoother.
When freshly laid, the structure may be lighter in color, such as white or pale tan, but it darkens over time to a shade of tan, brown, or gray that helps it blend into its surroundings. Internally, the case contains dozens to hundreds of individual eggs. This protective shell houses the eggs until the following spring.
Typical Placement of the Egg Case
The female mantis selects a location for her ootheca, typically in late summer or fall, so the eggs survive the winter. Attachment is achieved using a specialized adhesive, which firmly bonds the case to a stable substrate. Placement is often on sturdy, low-hanging branches, thick stems of shrubs, or tall grasses.
The ootheca is frequently found on non-plant surfaces as well, including fences, wooden decks, garden stakes, or the vertical sides of buildings. A common factor in site selection is the need for a stable, elevated location to hold the female’s weight during the laying process. This elevation also helps protect the eggs from ground predators and flooding.
The Emergence of Nymphs
The eggs inside the ootheca develop throughout the winter months, entering a state of dormancy known as diapause. Hatching is typically triggered by rising temperatures in the late spring or early summer. This timing ensures that the newly emerged young have an immediate supply of small insects to feed on.
When ready, the mantis nymphs, which resemble miniature, wingless adults, emerge en masse from small openings or slits in the egg case. A single ootheca can yield anywhere from 100 to 200 or more nymphs, depending on the species. They are immediately predatory and quickly disperse to avoid cannibalizing their siblings. The newly hatched nymphs are vulnerable, but they quickly begin molting, shedding their exoskeleton multiple times as they grow.
The empty ootheca remains attached to the surface, appearing as a weathered, hollow brown husk. The presence of this empty case confirms that the next generation of mantids has successfully hatched.