The process is horrific, but the ending is satisfying. Come and see how the cockroach died.

How annoying are cockroaches?

It is really impossible to drive it away or kill it. It pops up from some corner of the house from time to time to make its presence felt.

However, in front of the flat-headed mud wasp, the cockroach may not be able to be arrogant.

01

Who is the Flat-headed Mud Wasp?

Let’s first get to know today’s protagonist – the cockroach’s nightmare – the flat-headed mud wasp (Ampulex compressa).

Flat-headed mud wasp, image source: iNaturalist

The flat-headed mud wasp is a member of the Hymenoptera family. Its sphere of influence is mainly concentrated in tropical regions such as South Asia, Africa, and the Pacific Islands, with the most dense distribution in India and Myanmar.

The distribution range of the flat-headed mud wasp. Image source: Global Biodiversity Information Facility

Like typical insects, the body of the flat-headed mud wasp is divided into three parts: head, thorax, and abdomen. It has three pairs of legs, slender antennae on the head, and two pairs of membranous wings on the back for coordinated flight.

The flat-headed mud wasp is not big in size, with females reaching more than 20 mm in length, and males being smaller. However, despite its small size, the flat-headed mud wasp is a ferocious carnivore by nature, and can easily deal with cockroaches that are much larger than itself.

The flat-headed mud wasp is only as big as the tip of a finger. Image source: iNaturalist

When you see the flat-headed mud wasp for the first time, you may be amazed by its beautiful appearance. Its body shines with blue-green metallic luster, and its feet are decorated with bright red, which looks very gorgeous.

The flat-headed mud wasp is very good-looking. Image source: Sharadpunita

However, in nature, "bright colors" always seem to go hand in hand with "poison". The flat-headed mud wasp is so beautiful, so it must be poisonous, right?

You guessed it right, the flat-headed mud wasp is indeed an expert in using poison, but only female wasps can secrete venom. This is because their venom has special uses and is closely related to the female's raising of offspring.

When a female flat-headed mud wasp is ready to lay eggs, she will attack cockroaches (especially American and Australian cockroaches).

02

Poor cockroach fell prey

At first glance, the cockroach is much larger than the flat-headed mud wasp, and its fighting ability should be stronger. It shouldn't be easy for the flat-headed mud wasp to kill such a "large prey", right?

The flat-headed mud wasp is significantly smaller than the cockroach. Image source: iNaturalist

In fact, the purpose of the flat-headed mud wasp is not to kill the cockroach, but to exercise "mind control" over it, and the weapon used is naturally its venom.

When the flat-headed mud wasp finds the target cockroach, it will find the right opportunity to inject the first venom into the cockroach (usually piercing the chest). Soon, the venom begins to take effect, and the appendages on the front thorax of the cockroach gradually become paralyzed, losing the ability to resist.

Then, the cockroach, unable to resist, is injected with a second type of venom by the flat-headed mud wasp. This venom is directly injected into the cockroach's head, acting on the head ganglion and destroying the cockroach's nervous system. After the venom takes effect, the cockroach completely loses its fighting power and becomes a "puppet" of the flat-headed mud wasp, allowing the flat-headed mud wasp to dispose of it.

The reason why the venom can cause cockroaches to lose their fighting power is that it can cause hypokinesia in cockroaches. The specific manifestations include an increase in the escape threshold, a decrease in the escape distance, and a decrease in spontaneous walking. Doesn’t it sound hard to understand?

In fact, the cockroach's ability to respond to external stimuli has deteriorated. In the past, it might have to run away quickly when it saw an enemy from a distance, but now it has to wait until the enemy gets close before it can react and run away, and it can't run far. This motor function reduction can last for 7-10 days, which is enough time for the flat-headed mud wasp to slowly squeeze out the surplus value of the cockroach.

So what is the value of cockroaches to the flat-headed mud wasp? Since we have already emphasized that it is a female mud wasp, the answer to this question is easy to guess - naturally, it needs cockroaches to help it raise its children. Yes, it uses the flesh and blood of cockroaches to raise them.

The larvae of the flat-headed mud wasp eat the cockroach until only the shell is left. Image source: Micro Beasts

The cockroach, which had become a walking corpse, became docile and tame, and under the guidance of the flat-headed mud wasp, it obediently walked into the cave dug by the flat-headed mud wasp on the ground. After entering the cave, the flat-headed mud wasp would lay eggs on the cockroach, and then carefully cover the hole to prevent it from being discovered by other predators.

In the next few days, cockroaches provide fresh food for the larvae of the flat-headed mud wasp. The first two stages of the larvae's development are external parasitism, mainly sucking the body fluids of cockroaches. When they develop to the third stage, they turn into internal parasites, drilling into the cockroach's body and starting to eat.

However, the larvae of the flat-headed mud wasp do not eat the cockroach's internal organs indiscriminately, but prefer skeletal muscles and less important tissues to ensure that the cockroach does not die immediately.

The process of the flat-headed mud wasp from egg to pupa, picture source reference [1]

As for the poor cockroaches, although they survived for a long time during the process of being eaten, they were powerless to change their fate and were eaten alive by the larvae of the flat-headed mud wasp. This was simply cruel. When the larvae finally grew up, the cockroaches had been eaten to only an empty shell.

A mature flat-headed wasp crawls out of a dead cockroach. Image source: Scientific American

03

A new way to kill cockroaches?

Seeing this, many people probably started to get excited. Although this flat-headed mud wasp is a bit cruel, it can kill cockroaches. There doesn't seem to be anything wrong in letting the cockroaches die miserably. Can it be used to deal with cockroaches?

Well, this idea sounds reasonable, and some people did it, but the expected results did not appear. In 1941, American biologist FX Williams introduced flat-headed mud wasps to Hawaii, hoping to use them to control cockroaches. However, the number of cockroaches killed by flat-headed mud wasps was really limited, and it was difficult to achieve the purpose of controlling cockroaches, and the plan failed.

On the other hand, facing the attack of the flat-headed mud wasp, cockroaches are not just sitting there waiting to die. Before the flat-headed mud wasp successfully injects venom, they also have a chance to "fight back" successfully. After all, cockroaches are much larger than the flat-headed mud wasp. Facing the opponent's "harassment", they will use their strong hind legs to kick the flat-headed mud wasp's head hard to repel the opponent and protect themselves from its "mental control".

References:

[1] Arvidson R, Landa V, Frankenberg S, Adams ME. Life History of the Emerald Jewel Wasp Ampulex compressa. Journal of Hymenoptera Research, 2018, 63: 1-13.

[2] Yang Wa, Muhammad Mahdi Karim. Flat-headed mud wasp[J]. Global Human Geography, 2016(19):114.

[3] Williams, FX. 1942. Ampulex Compressa (Fabr.), A Cockraoch-Hunting Wasp Introduced from New Caledonia Into Hawaii. Proc Hawaiian Entomol Soc 11(02): 221-233.

END

Reviewer: Ran Hao, well-known popular science writer

Tadpole Musical Notation original article, please indicate the source when reprinting

Editor/Heart and Paper