31 May 2016

My Ant Symbiosis Stories



This post is a little off topic from my normal posts.  Although, since I consider my blog to be about programming, software engineering, math and computer science, perhaps taking a brief foray into the natural sciences is warranted as it is science and I am a science nerd, and of course it is my blog.  The book that I am referencing for this post is: The Ants by E.O. Wilson and Bert Hölldobler. It has many great examples of data visualization.  There is also a CS relevant area of study called ant hill algorithms.  Additionally, I believe that the study of social biology is basically just game theory which again is a topic that comes up in CS.


The natural world is fascinating and it teams with many interesting life and death stories that play out every minute of every day in the theatre of nature.  Some of the most fascinating plots include various types of symbiosis that occur between species. Symbiosis, also called mutualism, is a cooperative relationship between two species that sometimes includes an exchange of “survival favors”.  A fairly famous example of this type of species interdependence is the story of why Brazil nuts produce very poorly in plantations.  It turns out the Brazil nut tree Bertholletia excelsa is dependent on a pollinator insect, an orchid bee Euglossa, which is attracted by an orchid, Coryanthes Vasquezii  which does not grow on the tree but is present in the undisturbed forest habitat.  Finally the tough outer shell needs large rodents like the Agouti to gnaw it open, they much like squirrels consume some of the seeds and also bury some for later which allows some of the forgotten seeds to germinate.  There are many examples of symbiotic relationships in rainforest and other habitats.


Ants are notorious for having symbiotic relationships with plants and other insects and many such cases are well documented. One case is the Neotropical Cecropia tree which provides hollow stems for Azteca ants to inhabit and even food in the form of gylcogen-rich Müllerian bodies.  There was another story about a relatively recent discovery of a plant that grows on the harsh cliffs of Pyrenees that depends on three species of ants for pollination and seed dispersal.  These types of stories are not uncommon in the natural world, however, one often reads of them playing out in the above and often exotic and/or tropical locations, so I found myself rather surprised to discover this type of drama transpiring literally inches from my living room window in suburban Arlington Virginia. 


The story I am going to tell happened during the summer of 2011 and I had originally labored under the assumption that it was a somewhat unique undocumented story.  However, my subsequent research has yielded a number of pictures which depict many of the events that I will describe and show here often with better photographic quality than what I what I captured.  Not that my photos are bad but they lack the fidelity of others I have seen.  I make up for this in quantity which captures various events over an extended period of time.


One of my hobbies is identifying eastern forest native plants and experimenting with growing them in my yard.  This activity, probably to the chagrin of my mcmansioned neighbors, has turned my yard into a small native plant and wildlife habit.   A few years ago I collected some seeds of a plant known as Yellow Leaf Cup, Bearpaw, or Bearsfoot, which I believe goes by the Latin name Smallanthus Uvedalia formerly known as Polymnia Uvedalia.  It is in the Aster Family (Asteraceae).  I planted some in pots and scattered some seeds in my yard, the potted ones germinated but did not make it however some took root right in front of my living room window.  To me this plant really stands out, for a temperate zone plant it has very large leaves, 12 to 18 inches long, and as a result it almost completely obscures my living room window shrouding it in giant green veined leaves as you can see in the picture at the top of this post.  The location of these leaves put me in a unexpected and unique position to watch an incredible and probably epoch old symbiotic drama of nature play out between Ants(Hymenopterans) and Hemipterans


In June 2011 as the stand of Large Flowered Leaf-Cup reached about eight or ten feet in height and completely blocked my living-room window providing a nice screen of green privacy, an odd looking insect, pictured below, showed up.  As you can see it’s shaped like a thorn which has garnered its ilk the general common name of thorn bug it is also referred to as a tree hopper this class of insects that falls under the order Hemiptera, and I believe it is the species Entylia carinata. It does not have a common name.  I think it needs a common name and in that picture I see a rhinoceros looking insect, thus I am coining it the rhinoceros thorn bug or just the shorter version of rhino thorn bug.  If you look closely at the picture below you can see its eyes and legs which are hard to see in many of the photos, my guess is this is by design as thorns don’t have eyes and legs.



Shortly after its arrival the ants showed up to tend to it:



I contacted a biologist who specializes in ants and he identified them as a species of carpenter ants in the genus Camponotus. He told me the possible species for this area are: Pennsylvanicus, Nearcticus, and Subbarbatus.


Over the following months I watched the interesting drama play out with these two species. Owning a copy The Ants gave some perspective to the traits and behaviors of these species.  Over time I captured over one thousand pictures of what played out between these two species.  This collection is really a dataset of photos and it revealed some interesting observations, which while not novel, still make for an interesting story.


Rhino Thorn Bugs: Masters of Camouflage


First let’s start with how Rhino Thorn Bug disguises itself.  A number of the photos of it were taken in different lighting conditions.  In the above photos the light is more direct and the yellow and green “veins” of both the plant and insect mesh and it looks like a thorn on the stem.  In the following lighting the Rhino Thorn Bug appears to have purplish veins that blend with the background of plant veins.



 Another outcome of the Rhino Thorn Bug living on smallanthus uvedalia is the damage to the leaves which also makes for a nice abstract photo:



I’m making a leap here, but it seems that this damage extends the camouflage range for the rhino thorn bug such that it can hang out on the leaf and look like damaged parts of the leaf that more closely match its brownish color and pseudo-veins in back lit conditions:



I also noticed that it seemed to stay in one place and was able to feed by making multiple bites into the thick main leaf vein, I suspect that the major vein might be a bundle of veins and it was tapping into individual sub-veins each time.  This is visible in a subsequent photo.


Protection and Feeding


Ant Symbiosis with other insects takes a number of forms. A common symbiosis is known as Trophobiosis where ants feed on what is known as honeydew.  This substance is a mixture of sugars that the insect excretes from its posterior.  It is often the case that the provider of this mixture breaks down more complex polysaccharides into simpler sugars that the ants can digest these include glucose, fructose, etc.   The not so great image below shows this an ant feeding from the posterior of the rhino thorn bug:



This relationship is not unfamiliar to humans. It seems to mirror our use of livestock especially dairy cows, although we get the fluid we consume from a different organ.  However, the behavior of protecting, caring for and in some cases herding these insects is exactly what we do with our livestock.  The ants have been doing this millions of years prior to our existence as the ant Hemiptera symbiosis behavior is thought to have originated in the Eocene period.  There is evidence of this, shown below, from about 15 million years ago found in Dominican Amber which shows a queen from the extinct species Acropyga glaesaria on her mating flight with a “seed” mealybug in her mandibles for use when she establishes her new colony.



Another ant behavior that I believe I caught is ants transferring food to each other, which is known as Trophallaxis.  In the image below you can see the two ants at the top with their mandibles interlocked, in a previous picture one of them was feeding and now seems to be transferring food to the other.



Castes


Ants have different castes of workers. The image below shows two different castes I observed.  The one at the top is a Major worker.  Ants of this caste are in some cases referred to as soldiers as they in some species take on roles like acting as “doormen” at colony entrances to ensure that only ants of that colony are allowed.  It easy to see that the larger body size with the large head and large mandibles makes them more formidable, although I don’t know if the solder distinction truly applies in this case.  The other two are minor workers which have smaller bodies and heads. 



Rhino Thorn Bugs, the Next Generation


As the story unfolded it got even more interesting. I recall, although I don’t have photos of it that the ants seems to escort the thorn bugs to meet each other for mating.  The evidence of mating was soon obvious as can be seen in the photo below with the ants in attendance of the brood of recently hatched nymphs.  The ants tended to the nymphs which included chasing them around as they wandered off. Some of the nymphs seemed to stray and many of them died.  Also visible in this photo are the multiple bites left by what was presumably the female rhino thorn bug made over her extended time staying in one location.



Pretty soon the nymphs are providing the same trophobiosis as their parents as shown below:



As the nymphs grow up you can see that they start to take on their adult shape:




The Next Year, New Ants and Aphids


I was curious to see if the thorn bugs would return the following year. They did not.  However, I was surprised to a whole new ant drama play out with new actors.   I reached out to the ant biologist who helped me the previous year and he identified these as Tapinoma sessile.  I was not able to identify the aphids.  I was told they would be plant specific.


Their activity was concentrated around the flowers and spanned the time that they were in bloom.  The “infestation” of the flower heads can be seen in the following photo:



Another difference was the ratio of ants to honeydew producers, as you can see there are many aphids to each ant which in contrast to the rhino thorn bugs which often had multiple ants in attendance of each one.  The biologist that I contacted said that the ants looked fat and happy, and their abdomens or gasters in ant biology speak, seem to be bursting and almost glistening, presumably with honeydew.   I once saw David Attenborough eat a honeypot ant and it got me thinking I should have tried it with these guys. Well that was until I learned that their common names include odorous house ant and stink ant.



The photo below shows how the flower’s sepal seems to serve as a protected staging area for the aphids to develop to full maturity:



All of this happened in 2012. I have not seen the aphids since. I do see the rhino thorn bugs at least one or two each year over the last few years.  I have never seen the level of activity that I saw back in 2011, I am always hopeful that each new year will bring some new drama. Actually last year it was an opiliones explosion, but that’s a whole other story. 


The story about the Brazil nut symbiosis is interesting and was a little bit of a setup to show my cute seed disperser below.  Although the plant is obscured by another (Wingstem, Verbesina alternifolia) It is collecting Large Flower Leafcup seeds, the flower heads are visible slightly right and below it.



References and Further Reading







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