Praying mantises often capture human curiosity. Many observers wonder if a mantis is “pregnant” when its appearance changes. However, insects do not experience pregnancy like mammals. Instead, a female mantis becomes “gravid,” a term describing her condition when carrying fully developed eggs internally, ready for deposition.
Mantis Reproduction: Beyond “Pregnancy”
The biological process in mantises differs significantly from mammalian pregnancy. A female mantis becomes gravid when her ovaries fill with fertilized eggs after successful mating. The male transfers sperm via a spermatophore, and a single mating can provide enough sperm for the female to produce several egg batches throughout her reproductive life.
Unlike live-bearing animals, mantises do not nourish developing embryos inside their bodies for an extended period. Instead, eggs are packaged into a protective casing externally. Mating typically occurs during warmer months, preparing the female for egg-laying.
Identifying a Gravid Female Mantis
Recognizing a gravid female mantis involves observing changes in her physical form and behavior. The most noticeable indicator is a significantly swollen or distended abdomen. This enlargement makes her abdomen appear notably larger and more rounded, often described as “bloated” or “fat.” This distension occurs as her body prepares to hold the developing eggs.
As she approaches egg-laying, her abdomen may become very large and firm. She might also exhibit subtle behavioral shifts, such as reduced activity, as her mobility becomes hindered by the enlarged abdomen. She may also show an increased appetite to gather nutrients for egg production, or begin seeking suitable, sheltered locations to deposit her eggs.
The Ootheca: Mantis Egg Case
After a female mantis is gravid, she creates and deposits an ootheca, a specialized egg case. This protective structure forms from a frothy substance secreted from glands at the end of her abdomen, which rapidly hardens upon exposure to air. The ootheca serves as a durable shield, safeguarding the eggs from environmental hazards like desiccation, extreme temperatures, and predators.
The ootheca’s appearance varies by mantis species, but it typically has a light tan or brown color that helps it blend with its surroundings. Its texture is often described as papery-bubbly or resembling spray foam insulation. Mantises commonly deposit these cases on twigs, stems, walls, fences, building siding, or on the ground. Each ootheca can contain from a few dozen to several hundred eggs, with some species laying up to 400.