Why Flies Get Drunk On Semen At Crime Scenes

Human blood, semen and saliva. These are all things that forensic biologist Dr Annalisa Durdle has fed to Blowflies to find out what they are most attracted to.

Her research helps investigators better understand how flies transfer DNA at crime scenes.

“They are most attracted to semen over all the biological materials, despite the fact it gets them drunk, it gives them diarrhoea and it kills them,” Dr Durdle said.

Dr Annalisa Durdle unpacks the ‘crack cocaine of the fly world’ on the Crime Insiders podcast:

Crime Insiders: Forensics host Kathryn Fox asked Durdle, “How do you know that a fly is drunk in the first place?”

“I use the terms drunk, but it’s really just losing its motor responses,” Durdle said.

Durdle conducted research using about 140 hours of footage of flies eating, pooing and vomiting. In the experiment, she presented flies with household items like honey, tuna and dog food, as well as human biological material like blood and saliva.

“With the semen, what I noticed with flies is they basically staggered around. They couldn’t walk properly, probably a bit like some people at 2 a.m. on a Saturday night in Melbourne”

Durdle said the flies also become partially paralysed and then die.

“But it’ll go straight back for the semen. I call it the crack cocaine of the fly world.”

How can fly poo be used to solve a crime? Dr Durdle explains on the latest episode of Crime Insiders.

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