If mantids are kept in captivity, the male almost always loses his life. But in the wild, the females rarely eat their mates. As with spiders, consumption of the male by the female provides her with the nutrients needed to produce her eggs, but well fed females normally do not cannibalize their mates. Production of more than 100 eggs and formation of the mantid's enormous foam egg cases require large amounts of lipids and proteins. Since the male's body mass is about one third the size of the female, he would contribute a substantial amount of nutrients to her reproductive endeavor.
Females are capable of producing three or four egg masses before they die, and usually mate several times with the same or different males. If each female ate each partner she mated with, many females would not have the opportunity to mate.
Approach
A receptive female emits a pheromone that announces her condition to nearby males. Like a male spider, the male mantis approaches the female with caution, making ritualized movements and leg posturing to reduce the chances of her attacking him. The male normally approaches from behind the female, stroking her sides with his long antennae and front legs and nibbling on her body as he moves forward alongside her.
Males change their approach behavior based on the risk of the female eating him - being far more cautious when she appears hungry than when she is well fed.
Often two or more males will court a female at the same time. If this is the case, the unsuccessful males leave immediately after one male is in position to mate with her. Moving beside the female, the successful male turns his ventral surface to the female, and copulation takes place with their abdomens close to each other.
Since he is only about two thirds the length of the female, by approaching her from behind, the male's head rarely comes into range of her rapacious forelegs. The unfortunate male who approaches from in front of the female may become nutrients for her eggs as well as the father of her children. This is not all bad because the death of the male ensures that his offspring have enough stored calories and proteins to survive the winter and rigors of hatching in the spring.
How Does the Male Complete the Mating Act While Being Eaten?
When the female decides to eat the male, she seizes and clutches him by the upper thorax and begins eating his head. Once the male's brain is destroyed, an abdominal ganglion causes the posterior portion of his abdomen to move in circles until his reproductive organs contact hers. Upon contact, his copulatory organ enters her and sperm transfer is made even though the male may already have a quarter or more of his body consumed. The onset of mating does not distract the female from eating, and she continues to consume the male until the last of his abdomen has been ingested.
Egg Cases
Once her eggs are mature, the female climbs a nearby plant stem and expels a foamy egg case inside of which she implants between fifty and one hundred and fifty eggs. The foam rapidly hardens into a waterproof housing that protects the eggs against freezing during the winter and a large percentage of the occasional fires that burn through the fields.
Each species' egg case has a characteristic shape, although several species' cases are similar to each other. The two imported Eurasian species, Mantis religiosus and Tenodera sinensis, produce rounded cases with flattened tops. These cases are attached to thin stems and the posterior surface wraps around the stem, holding it tightly within the foam edifice. The native Carolina mantis, Stagmomantis carolina, produces an oval case that tapers toward both ends and often has a flattened back. These cases are usually bonded to a wider surface such as a trunk or major stem, but it may also wrap around the stem if a flattened object is not available.
Hibernation
Although adult mantids die from depletion of nutrients or when temperatures drop below freezing, their eggs contain organic antifreezes, enter a state of diapause where most metabolic activity ceases, and can withstand exposure to sub-zero temperatures. To ensure the young will not freeze to death in the spring, three or more weeks of temperatures over fifty degrees Fahrenheit are needed to trigger the embryos to develop and hatch.
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