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Why the praying mantis eats its mate

The Praying Mantis

The Praying Mantis   | Photo Credit: Lakhan Kohli

The Praying Mantis (Mantis religiosa inornata) is named for its prominent front legs, which bend to assume a position of prayer. A large insect belonging to the family Mantidae or Mantids, this subspecies of the European Mantis, is about 6 cm to 7.5 cm in size and is found across the Indian subcontinent.

Poised on a long ‘neck’ is a triangular head, with an ability to turn a complete 180 degrees. This helps the mantis scan its surroundings for prey and any imminent threat nearby. Both males and females have two pairs of wings, but due to the sheer size and weight of the female, its wings do not support flying, while the males are more active and can take short flights.

Their hunting prowess and male-female interaction is highly reliant on their ability to see. Vision, being the cornerstone of their survival, is aided by two big bulging compound eyes to detect the slightest movement, and three smaller simple eyes between the two big eyes, to detect light. Another unique feature is the metathoracic ear that processes high and low frequency sounds, even in the ultrasound spectrum.

A strategic ambush predatory instinct, exceptional camouflage, patience and lightning fast reflexes often escaping the naked eye, make it one of the most formidable hunters of the insect world. Its earthy tones of green or brown help it hide in plain sight, all the better to stalk its prey patiently. The front legs (also called raptorial legs) are armed with spikes to snare prey and restrain them to avoid a miss-hunt. Moths, grasshoppers, and other insects and invertebrates attract their attention. When threatened by a predator, it stands erect with its raptorial legs raised over its head, to look bigger than it is.

Experiments conducted as early as 1904 by Di Cesnola, then a student at Oxford, and a pupil of WFR Weldon, a renowned biologist, showed that the green morph (appearance) were found in areas with green grass, and the brown morph preferred areas with flora that was brown. These experiments formed the basis of our understanding of its the camouflaging purpose of its colouration. In the experiment, cannibalism was also extensively seen, where even the nymphs (juveniles) feed on each other, if given a chance.

Its mating behaviour is widely known: The bigger adult female devours the male after, or sometimes during, the mating process, for nutrition. This behaviour doesn’t seem to deter males from reproduction. It does make them wary of the female’s size and strength at times. So males use the ‘stop-and-go’ tactic, which helps them stalk females without being detected.

Praying mantises mostly cannot see stationary objects so males generally freeze if they see females move or turn their heads. Though males try and escape as soon as the mating is complete for their own safety, a lot of them end up being eaten. Post mating, females lay hundreds of eggs in an egg-case.

With the onset of the monsoon, look out for these stealthy ninjas on plants around you. You’ll see them until the beginning of winter. In Delhi-NCR we sometimes find other mantises like the Indian stick mantis that grows up to 13-15 cm. It walks vertically, unlike a stick insect that has a horizontal posture. There is also the flower mantis that stays on flowers the colour of its body, and the bark mantis that has the colour and texture of the tree bark.

The writer is the founder of NINOX - Owl About Nature, a nature-awareness initiative. He is the Delhi-NCR reviewer for Ebird, a Cornell University initiative, monitoring rare sightings of birds. He formerly led a programme of WWF India.

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Printable version | Aug 7, 2020 11:41:31 PM | https://www.thehindu.com/sci-tech/energy-and-environment/why-the-praying-mantis-eats-its-mate/article32029924.ece

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