Endoparasitic wasps deposit their eggs into fruit fly larvae. The eggs hatch inside the larvae and eat the fruit fly larvae inside out. The threat is so real to the fruit flies that when the flies sense the presence of enemy wasps, they reduce the number of eggs laid to protect their young.

The fruit fly has three ways to protect itself against wasps: preventing the wasps from injecting their eggs into the larvae, using their immune system to kill the parasites and destroying the eggs of wasps before they hatch.

#1 Prevention is better than cure

According to a study led by Balint Z. Kacsoh published on July 19, 2018, in PLOS Genetics, fruit flies warn each other when parasitic wasps are nearby.  When fruit flies spot parasitic wasps in the vicinity, they inform each other, including relatives of different species.

Female fruit flies communicate with each other using wing movements and scents. The fruit flies respond by laying fewer eggs even when they have never seen a wasp previously. The communication is not effective among different species, but it quickly improves after different species cohabit with each other. The fruit flies learn each other's dialect and work together to minimize the wasp threat.

#2 Immune system

The fruit fly immune system works to kill the parasites before they hatch, but the wasps have developed a way to go around the fruit fly defenses. The wasp releases venom that suppresses the fruit fly larvae's immune system, rendering it useless.

#3 Using Alcohol

According to a study by Emory University published in March 2013 in The News-Letter, fruit flies lay their eggs in alcoholic environments to protect the larvae from parasitic wasps.

While fruit flies drink alcohol in rotting fruits with ease, wasps find it hard to tolerate alcohol, and their eggs die when the environment in the fruit fly larvae is alcoholic. The fruit flies dip their eggs and feed their young on fermented fruit as a protection against the wasps.

By employing the above tactics, fruit flies can guard against annihilation.