The praying mantis is widely known for its dramatic mating ritual, which sometimes ends with the female consuming the male. This phenomenon, known as sexual cannibalism, occurs when the female consumes her mate before, during, or after copulation. While the act appears brutal, it is a reproductive strategy that provides significant benefits for the female and, ultimately, the male’s offspring. For the male, the encounter is risky, but the potential for successful fertilization often makes the gamble worthwhile. The underlying drive is rooted in the biological imperative to maximize reproductive output.
The Evolutionary Drivers of Cannibalism
The primary explanation for why this behavior persists is that it enhances the female’s reproductive success through two distinct mechanisms. One benefit is a substantial nutritional gain, as the male’s body provides a meal rich in protein and amino acids. Studies show that when a female Chinese mantis (Tenodera sinensis) consumes her mate, nearly 89% of the male’s material is incorporated into her reproductive tissues and eggs. This direct material investment results in an increase in the number of eggs laid, with cannibalistic females producing, on average, 51 more eggs than their non-cannibalistic counterparts.
The second hypothesis relates to the mechanical efficiency of sperm transfer. The male mantis’s head contains a neural ganglion that inhibits copulatory movements. Decapitation removes this inhibitory center, allowing a separate, stimulatory ganglion in the thorax or abdomen to take over, resulting in more vigorous and sustained copulatory movements. This can lead to prolonged copulation, ensuring that the maximum amount of sperm is transferred, thereby increasing the male’s chances of successfully siring the female’s offspring.
Contextual Factors Influencing the Act
The occurrence of sexual cannibalism is not a fixed event but is highly influenced by the female’s physiological state and the specific species involved. The most important factor determining the male’s fate is the female’s level of hunger, as cannibalism functions as a form of adaptive foraging. Females in poor body condition or those that are food-deprived are more likely to attack and consume a male, as the meal is a necessary resource for egg production.
The frequency of the act varies dramatically across the roughly 2,000 different mantis species. For instance, the Springbok mantis (Miomantis caffra) exhibits a high rate of cannibalism, with approximately 60% of encounters ending in the male’s consumption. In contrast, the rate for the Chinese mantis is closer to 28%. High rates often observed in laboratory studies sometimes overestimate the frequency in natural environments. In the wild, sexual cannibalism is estimated to occur in a range of 13% to 28% of mating encounters, suggesting it is a significant threat to males.
How Males Attempt to Cope
Male mantises have developed several behavioral strategies to maximize their chances of both mating and survival. The most common tactic is caution and stealth, with males often approaching the female slowly and from behind to avoid detection and predatory strikes. This behavior also extends to their mate choice, as males in some species prefer to court well-fed females, who pose a lower risk of cannibalism because their nutritional needs are already met.
Some species have evolved active measures to counter the female’s aggression. Male Springbok mantises, for example, initiate wrestling matches to subdue the female before copulation begins. If the male is successful in pinning the female down with his raptorial forelegs, his chance of escaping cannibalism and successfully mating increases. Ultimately, for the male, the cost of being eaten is weighed against the genetic benefit of ensuring his genes are passed on through a well-nourished, high-fecundity female.