Researchers have confirmed that an entomopathogenic fungus that kills insects, better known as the "Zombie Ant Fungus," kills its host outside its nest so it can spread more rapidly.

The zombie ant fungus, whose scientific name is "Ophiocordyceps unilateralis," manipulates the behavioral patterns of an infected ant, mostly tropical carpenter ants (species Camponotus leonardi).

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The zombie ant fungus compels the infected ant to climb up vegetation and bite hard into the underside of a leaf, securing the ant to the plant when the ant dies.

A fungus stalk or a "stroma" erupts from the ant corpse (thinks of the "face hugger" from the movie, Aliens) and infectious spores or "ascoma" are dropped onto the forest floor.

When they fall, the fungus hits other ants, turning these ants into zombies and continuing the fungi's reproductive cycle.

The question puzzling scientists is why the fungus doesn't command the infected ant to return to its colony where it can infect other ants en masse.

Research has confirmed that fungal reproductive activity takes place outside the ant colony because of the ants' social immunity, said David Hughes, the first author of the research paper and an assistant professor of entomology and biology at Penn State University.

He explained that previous laboratory studies showed that social immunity is an important feature of ant societies

He believes that for the first time, scientists are able to find evidence of social immunity in ant societies under field conditions.

Hughes explained that ants are remarkably adept at cleaning the interior of their nest to prevent diseases. Fungal parasites don't have the ability for transmission inside the nest whether there are ants or not, he said.

He thinks this might be because the physical space and microclimate inside the nest doesn't allow the fungi to complete its development.

To compensate for this, the zombie ant fungi then create a "sniper's alley" through which they can easily move to another host.

This causes the parasite to not develop mechanisms that can overcome the social immunity that occurs inside the nest, he stressed.

Researchers said they didn't observe colony collapse despite the prevalence of the fungi in ant colonies.