Camouflage. You're doing it wrong.

Or the slick biofilm on the rocks in the springs in Zion.

Or this sign at on  the Navajo / Queen’s Garden trail in Bryce Canyon:

Briefly, once infected, the ant’s behavior is hijacked to  act as a delivery system for the fungus, which is finding a  good location to die and infect more ants.

Ants biting the underside of leaves as a result of infection by O. unilateralis. The top panel shows the whole leaf with the dense surrounding vegetation in the background and the lower panel shows a close up view of dead ant attached to a leaf vein. The stalk of the fungus emerges from the back of the ant's head and a bulb, the perithecia, from which spores are produced, grows from one side of this stalk, hence the name unilateralis. Reproduced under CC from PloS ONE

Nevertheless  the ants have developed behaviors that protect them from infection. The fungus infects on the ground, so the ants  build their nest in the forest canopy. They also forage in the canopy Although the canopy contains less food than the ground, the canopy is safer.  Still , there are a few ant trails leading to the ground, where the spores of the horrible head-splitting fungus lurk.

There is an idiom in Hebrew: “avodat nemalim” or Ant’s work. It means a repetitive task  that requires precision and takes a long time. Pontoppidian and colleagues have done exactly that: they selected a swath of 1200 m² in the Thai jungle, and looked under each and every leaf there; how is that for “Ant’s work”? They discovered something quite bizarre: the ants clustered in “graveyards”: there were areas where there were considerably more dead ants. Also, within those graveyards there were even denser clusters. Below is a schematic showing the ant nests locations (in the canopy), the foraging area in the canopy (orange), the ant trails in the canopy and on the ground, and the graveyards are marked as green  circles, with the denser clusters marked in darker green inside.

Reproduced from PLoS ONE under CC

It is not clear why the dead ants cluster in those graveyards. Is it just a result of the nests’ locations? Or is it yet another fungus-induced modification of the infected ants’ behavior that somehow benefits the fungus? The researchers found some correlation between the graveyards’ locations and microclimatic conditions, but nothing that would immediately explain the existence of graveyards. Those clusters of dead ants with fungi sticking out of their heads are still a mystery.

Excerpt from a documentary about Cordyceps. Different species of fungus and ant though.

Pontoppidan, M., Himaman, W., Hywel-Jones, N., Boomsma, J., & Hughes, D. (2009). Graveyards on the Move: The Spatio-Temporal Distribution of Dead Ophiocordyceps-Infected Ants PLoS ONE, 4 (3) DOI: 10.1371/journal.pone.0004835