Spray blood to avoid being eaten

In order to become a difficult item for predators, armor crickets have a great ability to spray blood out and vomit food out of their mouths whenever they are caught to make the enemy terrified.

Some insects - like beetles and elephant grasshoppers - are always actively spraying blood out of their bodies when attacked, but for decades the scientific community has not understood the benefits of this behavior.

Two Bill Bateman entomologists (University of Pretoria in South Africa) and Trish Fleming (Murdoch University of Australia) decided to decipher the mystery by tracking the cricket cricket (Acanthoplus discoidalis). This is an unidentified insect that lives in grasslands in Namibia, Botswana and South Africa. They have relatively large bodies (up to 5 cm long), strong jaws and a large horn at the back of the head. The legs, backs and horns of the cricket armor have many sharp spines. Males can emit deafening sounds by rubbing body parts.

Insects always take advantage of all physical features to deal with predators (such as lizards, birds). However, the cricket armor has two extremely strange tricks to escape. First, when meeting an enemy, they spit out the mouths of things they just ate. Second, they pump blood out of the body through holes in the back (right behind the head) and under the feet.

An armor cricket.(Photo: Bill Bateman)

When Bateman and Fleming caught crickets by hand or tweezers, they reacted differently according to the situation. If caught from either side, crickets are loud and find a way to bite the attacker. Then they spray blood through the holes in the body. If attacked from above (the direction they cannot bite), the crickets will spray blood from the beginning. Sometimes their blood sprayed into rays of up to 6 cm high.

'The blood of armor crickets is light green and has a pungent odor. It's like the taste of cigarettes on your fingers , 'Bateman said.

The two researchers continued to test the reaction of armor crickets when they saw the lizard. When they put a male cricket in the cage with 4 lizards, a predator rushes towards the cricket. Immediately crickets spray blood out of the body, forcing lizards to prey and clean the jaws. The second lizard also grabbed crickets and the same thing happened. The third lizard moved towards the cricket but did not attack.

Bateman tried the effect of blood and the food that the crickets vomited by spreading blood-like paint and food on several bodies. He then placed the crickets in cages with lizards. The results show that the lizards feed on all ' clean ' crickets, but they ignore the ones that are lightly green (the color of the blood). However, not all crickets painted in color are escaped. This proves that the crickets' blood is more frightening than the food they vomit.

The cricket's complex defense mechanism surprised Bateman. For example, they can adjust the direction of the blood ray so that the blood can fire at the enemy . Female crickets (incapable of making loud noises), regularly spray blood, bite and vomit food more than males.