Zombie Ants!

The Halloween season brings in hordes of scary creatures, from vampires to monsters to mummies. If we only look to the ant world, we can find all three. But these are not the scariest Halloween creatures to be found among the ants.

Ant Zombies!
In the tropical regions of the world, millions of ants are following the whims of an infection, possessed by a parasite that controls their brains for its own nefarious purposes. After maneuvering the ant into ideal position, this infection kills the vessel insect and explodes from its scull to give birth to more of its kind. Meet the Ophiocordyceps fungus and the ants it controls.

ant-zombie1

Photo Credit: David Hughes of Penn State / CC BY-NC 2.0

 

Ophiocordyceps. unilateralis is the villain in this horror story, a fungus that attacks ants and takes over their brains. Known as the “zombie fungus,” O. unilateralis attaches to the unsuspecting ant and breaks through its exoskeleton. The fungus spreads through the insect, producing chemicals that manipulate the ant’s behavior. The infected ant roams drunkenly, falling from high in the trees and erratically moving around on the forest floor, until the sun reaches its full height in the sky, at which point the ant ceases its wanderings. Under the influence of the zombie fungus, the ant chooses an ideal leaf. It bites down on the large vein of the leaf, and the ant’s jaw locks. The death grip is maintained until the ant dies and even after, as the fruiting body of the fungus explodes from the ant’s head, releasing its spores to infect more victims.

These unfortunate ants can be found in graveyards optimized for fungal growth (the correct temperature and humidity), and other ants actively avoid these sites, foraging in areas away from their dead peers.

Even movie makers are beginning to note the zombie ants. David Hughes, a leading expert in O. unilateralis, consulted for the movie World War Z and the videogame The Last of Us, lending real-world science to fictional zombies. The Last of Us imagines a mutated form of Ophiocordyceps that can infect humans, but we don’t have anything to fear from the zombie fungus anytime soon. The fungus has been specialized on ants for at least 48 million years, as fossil evidence shows. So humans don’t have to worry, but other bugs still need to keep their zombie defences high. There are strains of Cordyceps that infect many different arthropods, including tarantulas, grasshoppers and stick insects. The caterpillar specialist Ophiocordyceps sinensis is even used medicinally by humans. It is considered a “miracle cure” for many ailments and high quality specimens can sometimes sell for up to $50,000 dollars a pound!

So how do you stop a zombie infection? Ideas vary, but the zombie ant fungus has its own fungal foe. When O. unilatralis is infected by this hyperparasite, it cannot produce spores. This metafungus keeps the zombie number low and the spread of zombie-ism from progressing too fast through the ants.

In short, you don’t need to go to the movies to see zombies. Just go to the tropics and stay wary of fungi trying to control your mind (especially if you are an ant!).

ant-zombie2

Photo Credit: berniedup / CC BY-SA 2.0

Photo From You: Insect Identification

About two weeks ago one of our readers submitted a photo of an insect for us to identify. Erin Mills, our resident entomologist, figured out what it was and is ready to teach us all about a new moth.

Photo Peter sent us to identify

This photo comes to us all the way from right outside of Almeria, in Southern Spain, wow! Peter was digging in his garden and dug up what he thought was a snake, or part of one. It turned out to be a moth pupa. He kept it until the moth emerged and took a picture of what he saw. The moth’s wings were not yet completely developed at the time of the picture, so I knew I had a challenge ahead of me! Also, I don’t consider myself an expert on European moths. Luckily for me, this particular moth had some very distinguishing markings and a very unique behavior.

This is called a Death’s Head Hawkmoth. It is one of 3 different species that share this common name because of the marking on the thorax that looks vaguely like a skull. All 3 species belong to the genus Acherontia, This particular species, Acherontia atropos, is perhaps the most well-known of these moths.  They are native to the Middle East and Mediterranean region of Europe. This is the only species that is found in Europe, the other two are Asian. This fact, along with the markings on it’s thorax and abdomen, made it easy to identify.  Peter made a comment that the moth didn’t appear to like being harassed and actually hissed at him. This was another dead giveaway! Death’s Head Hawkmoths actually have the unique ability to make a squeaking noise by forcing air through their proboscis to deter predators. This is probably what Peter heard and described as a hiss. This is among several other unique features and behaviors of these moths.

Tomato Hornworm (5-Spotted Hawk Moth)
Creative Commons License photo credit: the_toe_stubber

They belong to the family Sphingidae, known as sphinx moths or hawk moths. Most sphingids have a very long proboscis that helps them to reach the sweet nectar deep inside of flowers. Death’s head moths, on the other hand, have an unusually short and thick proboscis. They have to find other ways of getting food, so they are known to raid bee hives for honey at night. They have a very thick exoskeleton to help protect them from stings and they are immune to the venom. Once inside the hive, they mimic the scent of the other bees, so for the most part they can move around the hive freely. Their thick, strong proboscis is perfect for penetrating the wax covering the honey cells. They will also feed on rotting fruit and tree sap. They can be a seasonal pest to some beekeepers.

 Click here for more information
on this poster

The skull pattern on their thorax has given them somewhat of a negative reputation. Their feisty disposition doesn’t help either. The caterpillars are known to make a loud snapping noise with their mandibles and will bite if they feel threatened. The squeaking noise of the adults has been compared to a melancholy cry.  They are often associated with death and the supernatural. You may recognize them from the movie Silence of the Lambs. In the movie and book, the trademark of the murderer was to place a pupa of this moth in the mouths of his victims. That in itself makes them seem kind of creepy! Also, all 3 of their scientific names are associated with death in Greek mythology. In Europe they were thought of as harbingers of war, death, and pestilence. Their appearance was thought to be a bad omen.  Of course this is all superstition and these are not harbingers of death, but just large beautiful moths, or are they??

Thank you so much for sending in the photo Peter, and I’m glad we could identify this insect for you! It’s amazing what you can find when digging in the dirt. Remember, if you find an odd looking bug and would like to know what it is, snap a picture and send it to us at blogadmin@hmns.org. Happy bug watching!

A Trick or a Treat?

In less than a week, people all over the country, including right here at our museum, will be celebrating Halloween. Perhaps your workplaces and schools are already festooned with ghosts, skeletons, graveyards, and the like.  If you stop and think about it, you may wonder just how it is that we came to celebrate by trying to disguise ourselves or by trying to frighten people.  Is this a trick or a treat?

Picket fence and yellow trees
Creative Commons License photo credit: joiseyshowaa

The short answer as to why we celebrate this time of year with images of death is that we are in the middle of autumn, the season when nature itself is dying.  To fully understand why we celebrate Halloween when we do, we must fully understand the seasons.

Earth orbits the Sun with its axis pointed at the North Star, Polaris. As a result, its axis is tilted by about 23.5 degrees with respect to its orbital plane.  This tilt, combined with Earth’s revolution around the Sun, causes the seasons.  If the North Pole leans towards the Sun, the Sun is higher in our sky and we get more direct sunlight.  Also, daytime is longer than nighttime.  As the North Pole begins to tilt away fron the Sun, the Sun appears lower and lower across the sky, and daytime gets shorter and shorter.  Eventually, the slanted-in solar rays and short days bring about winter.  Very cold air masses form in the darkened Arctic and begin to move south, some of which can even reach Houston.

Keep in mind that the Earth’s axis does not tilt back and forth; it points at Polaris the whole time.  In June, the North Pole is leaning towards the Sun, but by December, the Earth’s motion has carried it to the other side of the Sun.  The North Pole, still tilting the same way, now leans away from the Sun.

A common misconception is that the Earth is closer to the Sun in summer and more distant in winter, and that is what causes our seasons.  In fact, Earth’s perihelion (closest approach to the Sun) occurs just after the new year (January 1-4), while aphelion (greatest distance from the Sun) occurs around the 4th of July.  Earth’s orbit is an ellipse, but the Earth-Sun distance does not change by enough to affect our seasons.

where are you?
Creative Commons License photo credit: shioshvili

In the cycle of seasons, there are four points of note.  At the March equinox, neither pole is tilted toward the Sun and the Sun is directly overhead at the equator.  The is the vernal (spring) equinox for us and the autumnal (fall) equinox for folks south of the equator.  At the June solstice, the North Pole is tilted as much as possible towards the Sun, and the Sun is overhead at 23.5 degrees North (the Tropic of Cancer).  This is the summer solstice for us and the winter solstice in the Southern Hemisphere.  At the September equinox, once again neither pole tilts toward the Sun, and the Sun is again overhead at the equator.  This is our fall equinox and their spring equinox.  At the December solstice, the North Pole is tilted as much as possible away from the Sun, and the Sun is overhead at 23.5 degrees South (the Tropic of Capricorn).  This is the winter solstice for us and the summer solstice below the equator. 

We generally think of these points as the beginning of spring, summer, fall, and winter, but it doesn’t have to be that way.  After all, nothing magically happens with our weather on these dates.  We could just as well consider these points the midpoints of each season.  In that case, the seasons would begin and end at points roughly halfway between the equinoxes and solstices, in early February, May, August, and November.  If the equinoxes and solstices are ‘quarter days,’ the points halfway between them become the ‘cross-quarter days.’

The ancient Celts of Europe appear to have divided their year in precisely that way.  Gauls living in what is now France used a calendar of twelve lunar months with a 13th month added every 2.5 years (similar to the Hebrew calendar today).  Their two most significant months were Gamonios (lunar month corresponding to April/May ), which began the summer half of the year, and Samonios (lunar month corresponding to October/November) which began the winter half of the year.  Julius Caesar noted that daytime followed nighttime in Celtic days.  By extension, the dark (winter) half of the Celtic year preceded the light (summer) half, making Samonios the start of their new year.

The Celts in the British Isles (Irish and Scots) also had festivals aligned with the cross-quarter days.  In early February was Imbolc (or St. Brigid’s day).  Weather predicting traditions of this day are preserved in our current Groundhog Day.  Traditional May Day celebrations are similar to those of the Celtic BeltaneLughnasadh, in early August, marked the start of the harvest. 

'' The Sentiment of Light''
Creative Commons License photo credit: jdl_deleon

The most important, though, was Samhain (pronounced ’sah win’, not ‘Sam Hane’, due to rules of Gaelic spelling), in early November.  This three-day festival marked the beginning of the winter half of the year and the start of the whole year, like Gaulish Samonios.  It was the close of the harvest opened at Lughnasagh, and the time for culling excess livestock.  At this time, the veil between the living and the world of the dead was considered thinner than usual, and people looked forward to meeting and communing with ancestors and relatives who had died.  A ‘dumb supper‘ was set aside for departed relatives.  To scare away unwanted spirits, people dressed in frightening garb.  Note that these spirits were considered unpredictable and possibly mischievous because they were not the familiar ancestors–not because they were particularly evil.  Divination was also practiced at this time, as people sought to predict whom they would marry or how many children they would have. 

Doing the math, you’ve probably figured out that Halloween is not quite halfway from the equinox (September 22) to the solstice (December 21).  But remember, the Celts used a lunar calendar.  They celebrated their festivals on a certain phase of the Moon, possibly full moon, occurring nearest the cross-quarter day.  Upon the adoption of the Julian calendar, which was not strictly lunar, the festivals were moved to the beginning of February, May, August, and November, although this meant they were no longer exactly on the cross-quarter days. 

Saint
Creative Commons License photo credit:
The Wandering Angel

In the eighth century AD, Pope Gregory III moved the church’s commemoration of the souls in heaven (All Saints’ Day) from May 13 to November 1.  Another name for All Saints’ Day is All Hallows Day.  (’Hallow’ is an older term for ’sanctify’ or ‘make holy.’  Think of ‘…hallowed be thy name’ from the Lord’s Prayer).  The next day became All Souls’ Day.  The day before All Hallows Day or All Saints’ Day is All Hallows Eve, or Halloween.  The traditions of Samhain, with its similar focus on honoring the dearly departed, were a natural fit for All Hallows Day and All Hallows Eve.

Halloween, then, is ultimately just one expression of the human need to come to terms with death as a natural occurence and to honor those who have gone before.  In the season of the fall of the leaf, with the Sun taking a slightly lower path across the sky each day, the natural world is going through its own ‘death,’ providing a perfect context for our own activities.  We can therefore think of Halloween itself as a treat, not a trick.

I wish everyone a Happy Halloween, with many more treats than tricks.