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Do fire ants cause weddings?

6 Sep

aka the “Correlation is not Causation” post

chart via Google Correlate

Google search activity for “fire ant” and “wedding gift” show a strong correlation.  (via Google Correlate)

While playing with Google Correlate recently, I discovered that lots of people tend to search for the term “fire ant” at the same times when lots of people search for the term “wedding gift.”  In fact, with regards to being the search term most strongly correlated with “fire ant,” searches for a “wedding gift” rank second only to searches for “fly traps.”  (I am uncertain if this latter represents an urgent need for pest control solutions or carnivorous plants, but I wish people luck in their quest.)

What does this mean?  Do fire ant stings somehow induce people with a desire to form government-recognized pair bonds, or at least acquire gifts for such events?  Does the proliferation of wedding cake cause outbreaks of ravenous stinging ant populations?  Could the fire ants themselves be the ones searching for the perfect, tiny wedding gift?

Or, more likely, does this correlation highlight the strongly seasonal nature of both these phenomena?  I’ll let you judge that for yourself and also tell you that the answer is that last one.  In fact, fluctuations in fire ant and wedding gift searches are more likely affected by fluctuations in temperatures, weather, and times that are convenient to fly in-laws across the country.  These similar direct causes (with the exception of vacation time and airfare, which fire ants tend not to worry about) probably lead to the indirect correlations.  This is a fun reminder that establishing causality can be challenging, and statistics must be interpreted with care.

Judging by the graph of search activity, the need to deal with both weddings and pesky fire ants peaks in summer months and tapers off sharply in the cold of winter, when presumably both ants and prospective happy couples go dormant for the winter.

Other notable seasonal search terms that correlate with “fire ants”:

“Wedding gift” on the other hand tends to correlate extremely strongly with terms involving golf, for reasons I will leave to some other scientist to explore.

When is a fly not a fly?

5 Jul
wingles army ant symbiote myrmecophile commensal

A wingless phorid fly from an army ant raiding column under magnification.

Here’s a pretty cool little critter.  This strange-looking bug is actually a wingless phorid fly that we captured running in a column of army ants in Arizona.  Army ants are somewhat famous for hosting a wide variety of myrmecophiles.

Line of marching ants.

A raiding trail of army ants.

Life of a carpenter ant

24 Jun
Camponotus brood - larva, pupa, cocoon

Carpenter ant pupa cocoon and first instar larvae.

Ants, like butterflies, are holometabolous and go through complete metamorphosis with an egg, a larva (~caterpillar), a pupa (~chrysalis/cocoon), and adult ant (~butterfly).  In ants, the larvae resemble small white grubs and cannot move by themselves–they are fed and tended by the worker ants.

Newly hatched ant larvae in brood pile.

Carpenter ant first instar larvae viewed under magnification.

The larvae are covered in fine hairs which help them stick together in clumps, making it easier for adult workers to move and tend them.  In fire ants, these hairs also help with rafting behavior, because they can trap a layer of oxygen around the larvae, helping them breathe and making them extra buoyant.  Rafting fire ant colonies use their babies as tiny floatation devices.  Please take a moment to consider the wonder of nature.

As they grow, the larvae molt several times, and each growth stage is referred to as an instar.  The larvae pictured above are extremely tiny because they are first instar larvae, having only recently hatched.

Inside an ant pupal cocoon.

A pupating carpenter ant larva after spinning her cocoon.

When the larvae are old enough they prepare to metamorphose into adults.  Some ants, like these carpenter ants, spin themselves into cocoons to pupate, while others, like fire ants, leave their pupae exposed.  Above, you can see an opened cocoon that contains a larvae that has not yet molted into its pupal form.

Additional fun fact: ant larvae have a closed digestive tract (I assume to prevent them from making a mess all over the colony.  It’s like the ant equivalent of diapers.). They poop for the first time when they molt into pupae.  Best line from a paper ever:  “…the larva defecates for the first time…. Workers help out.” (Taber, 2000).  This is also the least appealing job description.

An opened ant pupa cocoon.

A carpenter ant pupa in her opened cocoon.

While the job of the larva is eating and growing, the job of the pupa is developing–reorganizing its system into an adult ant.  Ant pupa look basically like unmoving, pale adult ants, darkening up right before their final molt to adulthood.  The newly molted ants are still fairly pale and soft-bodied.  They are referred to as “callows.”  Their exoskeleton darkens as it hardens, until they are prepared to go about the daily business of an adult worker ant.

Magnified camponotus ant.

Adult carpenter ant worker.

PS:  Here is a cool video of a queen ant helping a pupa shed its old larval skin.

Fighting ants and Freeloading flies

17 May
Harvester ants fighting chopped in half on a rock

Harvester ants fight while a freeloader fly awaits the spoils of war.

I snapped this picture of fighting harvester ants in Arizona, and it wasn’t until I could see the images under the camera’s magnification that I was able to notice a few cool details.  First, please note that this is not in fact, two harvester ants fighting, but rather two and a half ants fighting.  These ladies are tenacious in battle.  Second, as I glanced through the series of pictures of this encounter I realized that one of the ants had a passenger.  (Or, perhaps, was showing off her lovely living hat.)  Paul Lenhart clued me in to the really interesting bit of biology playing out here.

Fighting ants and fly

Harvester ant tug-of-war, with freeloader fly looking on.

The fly riding out the fight atop one of the ants’ heads belongs to the family Milichiidae, the freeloader flies.  These very small flies are best known for the members of the family which make their living as commensals or kleptoparasites of predatory insects.  The adult flies hang out near predators, such as spiders or assassin bugs, and sometimes even ride along with them (attendance) awaiting the opportunity to sip up fluids exuded by wounded prey.

Harvester ants fighting and wrestling

Freeloader fly rides out a fierce ant tussle.

Much like mosquitoes and blood-feeding, in many species only the female exhibits this parasitic behavior, presumably because she needs a high protein diet to lay her eggs.  Some myrmecophilous species (ant-loving) have developed such a specialized relationship they even directly solicit ants for food via regurgitation or have larvae tended by worker ants in the nest.  In some cases this interaction takes the form of a “mugging.”  The flies pursue an ant, and, if they can successfully grab hold of the head by gripping the end of the antennae, the ant will then freeze and the fly can extend its proboscis into the ant’s mouth and trigger the regurgitation reflex (Wild & Brake, 2009).  As always, Alex’s pictures are impressive, so if you can’t access the paper figures definitely check the subset in his gallery.

How not to kill fire ants

10 May
A colony of fire ants (Solenopsis invicta) swarms in response to a disturbance to the mound.

Never attempt to drink fire ants.

Fire ants are the little devils that we here in the south love to hate. As such, there’s a sort of popular mythology that has risen up around them and the methods for getting them to go away.  Browsing forums around the net you can collect these bits of entomological folklore by the dozens.  Some of them are useful and some… not so much.

Blow ’em up

For example, there’s the ever-popular “grits will make things explode” theory as applied to ants:

“i heard that corn meal (ya know the stuff you can use to make corn bread) is something i heard kills them, they bring it to their nest … and they eat it, but they cant digest it so they explode (not literally, i wish they did though) so they just bloat till they die.”

Leaving aside the likelihood of grits causing anyone to explode there is one gaping flaw to this “common sense” theory.  While corn grit is used as a foundation for several commercial baits (such as Amdro), the key ingredient is the poison-laced oil the ants lick from the surface of the grits.  In fact, due to a sieve plate in their mouths and a constriction in their gut, most adult ants cannot chew or swallow solid food.  Instead, this job falls to the older larvae, who chew and partially digest solid food brought to them by the workers before sharing it via regurgitation.

Ants feed the colony and the queen dies - inaccurate fire ant art

Sorry, Amdro artist, that’s not quite how it works.

Before the evolution of trophallaxis (food sharing by regurgitation) the worker ants apparently acquired their nutrition from the larvae more directly. For example, dracula ants chew through the skin of their young and drink their “blood.”

Let them eat nutrasweet

Death by explosion seems to be a popular predicted outcome of various home remedies… possibly a case of vengeful sadism in response to one too many painful bites.  Still, artificial sweetener?

“The local news put a story about using Equal sugar substitute (I think it is in the blue packages?) on ants – it makes some ants explode. So, it’s bad for people and for ants.. go figure!”

I, personally, have never managed to make ants explode (and believe me, I’ve tried*).  According to Snopes this misconception arose around the same time as a satirical article which claimed that aspartame was first developed as a pesticide before companies “realized they could make a lot more money on it as a sweetener.”  That is to say, it’s a hilarious suggestion, but not true.

Doesn’t mean there aren’t videos about it, though.

…a few explosions would improve this immensely.

Spice things up

“When I lived in Florida, I used powdered cinnamon on the the mounds that were near plants I wanted to work with. This would keep them from crawling out of that mound until a good rain washed it away, then they would come out of there again.”

I can’t speak from any personal experience of fire ants interacting with cinnamon (although one researcher found the cinnamon treatment actually increased ant activity compared to untreated colonies).  There’s another flaw in this methodology, however.

If you watch a fire ant mound you will observe very little activity of ants coming and going from the body of the mound.  In fact, few people realize that fire ants use complex networks of underground tunnels for much of their foraging activity.  A single large colony may have more than a hundred meters of underground tunnels criss-crossing its territory like a subterranean highway system, the entirety of which it can construct (or reconstruct) in under two days (See Tschinkel’s The Fire Ants).  You may have noticed lines of excavated dirt from these tunnels running along the ground after a rain.  Such tunnels allow the workers to shelter from enemies and the heat of the day as they fan out in search of food.  Workers will even sometimes partially bury or cover over food resources they find.  (This is inconvenient for the researcher attempting to count foragers visiting sugar vials in the field.)

Kill them with kindness

Speaking of sugar vials.

“Fire ants hate sugar. If you have ever tried putting out a sugar bait for fire ants, you know what I mean. They will walk a mile to avoid some sugar.”

This is my personal favorite because it is pretty much the complete opposite of true.  Fire ants LOVE sugar.  Yes, they are opportunistic omnivores, and yes, they will scavenge on almost anything made available to them, and yes, proteins and lipids are pretty essential to the development of their young, but simple sugars are tops in terms of maintaining an energetic, active workforce which promotes colony growth.  (Also applies to humans.)

“Your fire ants are different from ours. Ours will absolutely NOT go anywhere near anything sweet. They only eat protein here.” (San Antonio)

Unless your type of fire ant is, say, a completely different species of ant, it’s unlikely the underlying biology and metabolism could accommodate such a radical shift in dietary preferences.  I’ve personally sampled fire ants across Texas, Mississippi, and even Argentina with both sugar and cricket baits, and let me tell you the sugar baits are hella popular.

Fire ants even seek out natural sugar resources, such as visiting extra-floral nectaries on plants (essentially sugar glands) or milking honeydew from aphids and other hemipterans.

Fire ant on cotton leaf drinking at extrafloral nectary.

Fire ant drinking at cotton extrafloral nectary.

Poison their fields and sabotage their supplies

A few of these sugar-based fire ant prevention tips recommend spraying sugar water, or watered-down molasses across your entire property, positing that this will promote microbial growth in the soil and drive off fire ants.

“The use of molasses actually stimulates the micro organisms in the soil, and this activity will drive away fire ants, actually, any type of ant.”

“If you spray or soak their mounds with anything sugary, the decomposition process speeds up on their food supply. The fire ants know this and will abandon a mound contaminated with sugar.”

I honestly can’t answer if there might be some kind of multi-tier effect whereby increased microbes or mold could in some way affect fire ant populations.  I dug through the literature but couldn’t find any study supporting this at all.  Color me skeptical.  If you’d like to draw your own conclusions, here are the few factoids I did dig up:

  • Activity for ant mounds treated with molasses was not significantly different than control mounds at any time (Vogt et al 2002).
  • Sinzogan et al recommends spraying mixes of water and sugar or molasses over fields to attract ants and enhance their foraging activity (2006).
  • Molasses has been used to control soil nematodes (Schenck 2001).
  • Molasses treatments may be good for your plant roots (Welbaum et al 2010).

I’d say that sounds like molasses treatments are a win for everybody!  Except maybe soil nematodes and the person trying to get rid of fire ants.

Wrath of the gods

But what about more direct (and dramatic) concoctions?  Vinegar and baking soda, that old paper-maché volcano stand-by is popular as a nest drench, apparently going for the “ant Pompeii” effect:

[whoops, the previous video got taken down.  here’s a different one:]

Meanwhile, a slightly less bubbly version employs club soda:

“I read where a liter of club soda will kill three mounds of Ants pour directly on ant (fire ants) and the Co2 will displace the oxeygen and sufficate them.”

Do these fizzy products actually work?  Elizabeth “Wizzie” Brown at Texas A&M has actually studied the effectiveness of this suggested fire ant cure, along with many other home remedies.  Unfortunately, things that sound too good to be true generally are.  Of the club soda remedy Brown says, “It also claimed that the club soda would leave no toxic residue, would not contaminate ground water and would not indiscriminately kill other insects or harm pets.  Pretty much all that part was true, but what wasn’t true was that it would be effective in killing fire ants, unless of course you happen to drown a few in the process.”

Set them on fire

Some people use a gasoline drench, with or without a match.  I’m not even going to link or quote any examples because this is really, really ILLEGAL.  And it’s hella bad for the ground water, which is even more vital of a natural resource then, say, fossil fuel.  Seriously, shame on you.

Other people employ less toxic things like fire crackers and while it’s probably not a very effective tactic, it’s certainly dramatic.

This is a fire fire ant.

Unfortunately, fizzy, flaming, or not, just dousing the mound probably isn’t going to succeed in drowning, suffocating, or exploding the colony.  Fire ants are well adapted to flood conditions.  Meanwhile, the mounds themselves are only a small part of a much bigger picture.  Fire ants use their mounds seasonally to moderate the temperature of the brood and adult ants.  It’s a great way to warm up after a long chilly night.  Beneath the nest, fire ants dig long, vertical tunnels with occasional flat, round chambers for living quarters.  (Dr. Walter Tschinkel compares them to “shish kebabs on a stick.”)

Seriously, though

“I have been fighting them for 20 years now. Spent tons of money and tricks that did not work. My father even tried to Pee on them. Nothing works.”

What does work?  Commercial baits and toxic drenches can poison the ants, while applications of boiling water provide a non-toxic alternative.  Less fatal drenches may still have some effect.  (For example, orange oil was found to reduce ant activity in one of the papers above.)  Fire ants move around naturally in response to environmental pressures, so sufficient disturbance may induce fire ant colonies to put up a satellite nest or relocate, hopefully to your neighbor’s yard.

Don’t feel too bad.  They’ll be back.

*My mom has a particular anecdote on this topic she loves to tell.  While she was at the door talking to a neighbor, 8-year-old me wandered up and asked “What do we have in this house that can make an explosion?”  I then wandered back into the house.  My mother decided to cut her conversation short.  Early adventures in SCIENCE.

How to Build a Bunch of Different Formicaria

18 Apr

Since my “Ant Farms: How to Build Your Own Formicarium” page is one of my most visited articles, I’ve created a page to compile some different ant rearing/formicaria designs that I have seen or used.

Please check it out!

Acrobat ants in a flat plaster nest.

Acrobat ants in a flat plaster nest.

Carpenter ants checking out air holes at the top of the stacked colony.

Carpenter ants checking out air holes at the top of a colony.

Monomorium minimum ants in with a tube ant nest.

Monomorium ants with a tube nest.

Rover ants and queen with brood in plaster nest.

Rover ants and queen with brood in plaster nest.

See more at:

Ant Farms: More formicaria designs

and see also:

Ant Farms: How to Build Your Own Formicarium


Dinoponera: Giant Killer Ants from the Amazon

5 Apr
Giant ant with big jaws.

Head and jaws of Dinoponera gigantea. (Photo courtesy Israel Del Toro)

Today’s post is about Dinoponera, which is a really freaking cool genus of ants, containing some of the largest species of ants in the world.  It is brought to you in recognition of my labmate Paul Lenhart’s new paper revising the genus, and also the following conversation:

Paul: What would I have to do to convince you to shamelessly plug my new paper on your blog?

Alison: Oh, okay, I can do that.  Send me some cool pictures.

Collin: At least ask for money.

Giant dinoponerine ant with stinger.

Dinoponera quadriceps with stinger visible. (Photo courtesy Israel Del Toro)

So some cool things about these South American ants.  The name Dinoponera translates roughly to “terrible devil,” or possibly “terrible painful evil thing.”  As I mentioned, Dinoponera can get quite large: Dinoponera gigantea workers get up to 3.6 cm, almost an inch and a half in length.  The stings and venom of these extremely predaceous ants are very strong and have been suggested to possibly be more painful than those of the infamous “bullet ants” (whose sting, according to popular lore, is like getting hit with a bullet).

New species of giant dinoponerine ant.

Newly described species, Dinoponera hispida. (Photo courtesy Israel Del Toro)

Dinoponera is one of a few ponerine ants which has lost the morphologically distinct queen caste.  Instead, to quote Paul directly: “one of the younger females becomes dominant, beats the shit out of the other ants, and her ovaries swell up and she becomes queen.”

Because this status is flexible, she is sometimes also referred to as the alpha female.  If she dies the process begins again, and another worker can step up to fill her place.  New colonies are formed when one of the beta females absconds with a cohort of workers, a process called fission.  Average colony size varies by species, and ranges from as small as about 10 workers to as large (if it can be called large) as 120 workers.

Giant winged dinoponerine male ant.

Winged male sexual of Dinoponera gigantea.  The genitalia have been removed for analysis.  (Photo courtesy Israel Del Toro)

The males are winged, but the females, since they are not a distinct sexual caste, are wingless.  Instead they wait at the entrance of the nest and mate with visiting males.  This is when things take a turn.  After mating, the female chews through the male’s gaster (basically his belly) to release herself. The male’s genitalia is left inside her.  This may function as a temporary mating plug, preventing her from mating with other males.

Nature! I can’t make this stuff up.

Sawtooth "chainsaw penis" of dinoponerine ant

The penis valve of newly described species, Dinoponera snellingi. (Photo courtesy Paul Lenhart)

It is possible the genitalia of the males are partially adapted for this “plug” purpose, as many have a barbed, sawtooth edge. In fact, one of the new species Paul and his coauthors described is most easily recognized by what Paul described as a “chainsaw penis,” a particularly strongly lobed “penis valve” with teeth running the length.  The newly described species is named Dinoponera snellingi, in honor of the late renowned entomologist and colleague, Roy Snelling.  I have no further comment on this subject.

Roy Snelling

The inimitable Roy Snelling.

One of the other new species, Dinoponera hispida, was described from specimens that were all collected in a single region of northern Brazil, called Tucuruí.  The only known location of this species has since been completely flooded, due to the construction of the Tucuruí dam, making it possible that this species became extinct before it was ever described.

Many insect boxes in the shelves of an insect collection.

The LA County Museum Holdings. (Photo courtesy P. Lenhart)

To write this paper, Paul and his coauthors looked at over 350 specimens and sought loans from collections all over the new world, as well as places like Germany and Italy, where holotypes (world representative specimens of the species) were preserved.  He also visited Ecuador and Argentina.  Paul said it was really cool to see types collected as far back as the 1800s.  On the other hand after years of work and thousands of person hours spent on this project he has still never seen a live Dinoponera ant.


Scientist observing ant taxonomy.

The life of a taxonomist: Coauthor Dr. Bill Mackay observing Dinoponera specimens at California Academy of Science. (Photo courtesy P. Lenhart)

Did I mention Paul has a new paper out?

Fire Ant Mating Flight

1 Apr

Following up the post from last Friday, here’s is some extremely dramatic and engaging cell phone footage of a mating flight of fire ants on a stump outside our lab.

Video courtesy Collin McMichael.  And yes, that is us having an engaging discussion about why this colony has not succumbed to our regular fire ant harvests:

Alison:  That is quite the flight.

Collin: I’m taking a video.

Alison: I guess when you nest in the base of a stump nobody messes with you.

Collin: Nope, no one digs you up.

Alison: Yeah. Can’t get mowed.

Gripping stuff.

PS:  I have updated my “Things That Are Not Fire Ants” page with 4 new images and 14 new pest control companies.  Clearly I am enjoying the Google “search by image” tool.

The Sad Plight of Male Ants (revisited)

29 Mar
Dead male winged ants in pile outside ant nest after mating flight.

Drifts of dead male alates.

Last fall I came upon this veritable drift of dead male fire ants, piled up along the sidewalk outside a large ant nest.  The worker ants there didn’t seem to know what to do with this sudden overabundance of dead bodies and were piling them up in heaps at the sidewalk edge and stuffing them into sidewalk cracks.

Dead male sexual fire ants on ground after nuptial flight.

Fire ants, like many social insects, mate in nuptial flights, swarms wherein thousands of winged sexual ants (alates) mate on the wing.  Afterwards, the females drop to the ground and shed their wings and become foundress queens, seeking out a place to rear their first brood.  The males drop to the ground and die.

Male alates drop to the ground and die after mating flight.

A male ant is pretty much a very streamlined sperm delivery device.  They hatch from unfertilized (haploid) eggs, they have big muscular backs for wing muscles, and tiny heads because they don’t need much in the way of brains.  Prior to their one and only flight they also void their gut contents and fill their abdomen with air to make themselves more aerodynamic (Wilson, “Insect Societies”).  After their mating flight the males may wander briefly on the ground for a period before their body inevitably shuts down and they die.

Male alates dead at the sidewalk edge.

The female alates, however, can go on to live more than twenty years.  Deborah Gordon has data on some of her long term study colonies of harvester ants going back to 1985.  Those colonies are as old as me!

Female alate fire ant explores nest hole.

Meanwhile a foundress queen sheds her wings and seeks a nesting site.

See also:

If you give an ant a cookie…

22 Feb
Harvester ants fighting to carry off a cookie crumb.

Pogonomyrmex and Aphaenogaster ants wrestle for a cookie crumb.

At the Southwest Ant Course last summer, I got the chance to participate in some cool biodiversity assays of the local ants, comparing assemblages before and after a flash flood.  Among other things, we pit-trapped, counted nest entrances, and scoured the ground for wandering ants.  To encourage ant activity, quadrants were sprinkled with cookie crumbs.  We were using crumbled up pecan sandies because, and I quote, “those are ants’ favorite cookies.”

I can’t speak for any given ant (I, personally, prefer Thin Mints), but the desert ants of Arizona certainly did seem to like pecan sandies.  I’m also going to go out on a limb and speculate that these cookies are useful as assay tools for their combination of sugars, proteins, and lipids in order to attract ants with a broad variety of diets.

Ants fighting for cookie

Two different species of desert ants continue to wrestle for a cookie crumb.

Pogonomyrmex (harvester ants) and Aphaenogaster (BugGuide calls these the “spine-waisted ants”) were by far the dominant species in the area.  The ants pictured above wrestling over a cookie crumb were in between two nests, and each was determined to get the prize back to her own colony.  I watched the ants play tug-of-war for several minutes, sometimes even picking up the cookie crumb with the other ant attached (as in the photo above).  Finally, the Aphaenogaster was joined by two of her nestmates, and the out-numbered pogo almost immediately surrendered the prize and fled the scene.  A rousing victory for Aphaenogaster-kind, who I assume went home to celebrate with cookies and tea.

Numbers win wars.

Aphaenogaster ants team up to wrestle a cookie crumb away from a lone Pogonomyrmex ant.

FYI, I believe these were Aphaenogaster albisetosa and Pogonomyrmex maricopa but don’t quote me on that.