Seeing Dead Flies Makes Other Flies Die Faster, But Why?

There might be a weird benefit to leaving dead flies where they fall on your windowsill.
Research has shown that when fruit flies of the species Drosophila melanogaster are exposed to the carcasses of their dead friends, their lifespan shrinks in a significant and measurable way.
They start acting withdrawn, lose body fat, and their aging accelerates to the point that they die sooner than fruit flies that don't see their dead buddies just lying where they fall like some macabre fruit fly graveyard.
And now scientists have a better idea about why this happens. Two neuron types receptive to the neurotransmitter serotonin become activated when fruit flies perceive dead comrades, and this increased activity accelerates the flies' aging process.
"Understanding the neural circuits through which death perception impacts these phenotypes may inform future work directed toward understanding the consequences associated with this, and perhaps other sensory experiences in individuals, including humans, and may provide insight into how specific neural states impact behavior and physiology," write a team of researchers led by physiologists Christi Gendron and Tuhin Chakraborty of the University of Michigan.
Seeing Dead Flies Makes Other Flies Die Faster, But Why?