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Note:  The following post is not for the squeamish. You probably shouldn't watch the videos right before lunch.

Seems like there has been a lot of press lately about the "zombie ants" caused by fungi of the genus Cordyceps. The afflicted ants stagger about before they die, hence the name "zombie." At the time of death the ant typically attaches itself to a leaf and becomes a stiff fungal-spore salt shaker.

David Attenborough gives a good introduction to the fungus:

Of course, myrmecologists have known about Cordyceps for a long time, but the new interest has lead to some cool new discoveries. In the article by Bateman, it is suggested that the chemical produced by the fungus that makes the ant stumble around may be similar to LSD. Also, weaver ant workers may be able to recognize diseased individuals and may have some behaviors to cope.

The video that accompanies the Bateman article:

Do you think this research would have gotten as much press if they had merely said the ants were infected by a fungus?

For more information:

Daytime bites for zombie ants:  Final death grip for the living dead of the insect world comes at midday by Susan Milius at Science News explores fungal infection of Camponotus leonardi.

Green ant 'zombies' affected by deadly fungus attacked by slayers - latest scientific research by Daniel Bateman

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This week we've been watching The Life of Birds DVD set narrated by Sir David Attenborough.  Have you ever seen the series? If you love nature you should, because it is so well done.

In one scene a rufous woodpecker from India is shown breaking open an ant nest and then busily eating ants. It piqued my curiosity, so I decided to see what else I could find out. Although I didn't find the exact scene online to show you, I did find videos of rufous woodpeckers eating ants.

This first video is rather dark, but shows two young birds feeding on ants.

It appears that these woodpeckers from the Kerala region of India specialize on ants. Vishnudas (2008) cites an earlier worker from 1912 who found 2,600 ants in the stomach of a rufous woodpecker.

Although this video is shaky, it shows another woodpecker going after ants. (Makes you appreciate the quality of the footage from the Attenborough DVD.) It cuts away as the ants come rushing out of their nest.

It turns out that Rufous Woodpeckers, Micropternus brachyurus, not only use ants as their main food source, but also depend on Crematogaster ants for nesting sites. The birds work together to open up the carton nests of Crematogaster ants, and then build their own nests inside.

In his paper, Vishnudas also reports that several other species of birds follow the rufous woodpeckers and feed on the escaping ants when the rufous woodpeckers tear ant nests open.

In North America, there are woodpeckers specialize on ants, as well.

Northern flickers probably eat the most ants. They spend much of their time feeding on the ground around anthills. One flicker was found to have 5,000 ants in its stomach.

Doesn't it look like the flicker is trying to dig out larvae and pupae rather than workers?

Pileated woodpeckers often cut slots into tree trunks or logs to get at carpenter ant nests inside. The woodpeckers will continue to return to the same opening over time, picking off ants that peer through the opening or that rush out to protect the nest.

It is fascinating to find out about these birds that are so dependent on ants for survival.

Have you seen any of the Attenborough series?

Reference:
Vishnudas, C. K. 2008. Crematogaster ants in shaded coffee plantations: a critical food source for Rufous Woodpecker Micropternus brachyurus and other forest birds. Indian Birds. 4:9-11. (Available from Google Docs as a free .pdf)

The The Life of Birds  DVD set:

The Life of Birds  book by David Attenborough

(Affiliate links to Amazon)

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One of the first things you notice about the Formica fusca group ants are their mounds.

(These photographs were taken in the Colorado Rockies).

Bare mounds of soil and small pebbles stand out amongst the vegetation.

As you get closer, you can see that the mound does have some brown bits of vegetation scattered about, such as dried conifer needles. There are also multiple entrance holes, something you don't see as much in the mound-building harvester ants.

Closer still and you can see the black ants with their large eyes. These ants are called the "Formica fusca group" because there are a number of ant species that can be hard to distinguish from one another. (See the resources at the bottom for more information.) My best guess about these are that they are part of the Formica subsericea complex, possibly Formica podzolica,, although they look a bit small.

Formica fusca ants get their common name "wood ants" because they live in forested areas or woods, not necessarily because they live in wood. Wood ants, or thatching ants as they are sometimes also called, are easily confused with carpenter ants. Typically the Formica ants are smaller than Camponotus, and the back of their alitrunk (midsection) has a valley or depressed area, rather than evenly rounded like the carpenter ants.

Many species build their mounds in the cooler forests of North America, Europe and Asia. Some of the wood ants cover their mounds with pine needles and bits of twigs, so they look like they have thatched roofs, even more than we saw in the photograph above. The piled up homes catch the sunlight and create a warm interior that allows these ants to live in colder places than most types of ants.

Wood ants feed on aphid honeydew as well as scavenge dead arthropods. They are also predators of common forest pests and are considered to be beneficial to the forest.

Wood ants lack a stinger. They defend themselves by spraying droplets of formic acid when disturbed, which causes most enemies to retreat. They also can bite.

At a nearby mound I noticed an interesting behavior that may have been related to defense. The workers were wrestling with a green aspen leaf that had fallen on the mound.

As you can see, the workers are chewing on and biting off pieces of the leaf.

In this video, you can see the same behavior. At the same time, the ants are apparently leaving the brown twigs alone.

Do you think it is sanitation? If they wanted to get rid of the leaf, wouldn't they simply cart it to the side and dump it? Do you think they using the bits of leaves for something? Or perhaps the moister leaves are more likely to mold and cause sanitation issues than the drier twigs and needles.

In any case, ants of the Formica fusca group are fascinating ants.

Resources:

Formica fusca group at Myrmecos.net

Navajo Ant Project

AntWeb