If you have a pool, you know that most insects don't have a chance if they fall into the water. Here at Wild About Ants, however, we know ants often do the seemingly impossible. To prove it, let's look at the ability of certain species of ants to swim.

Camponotus-pennsylvanicus-very-cool

In a recent article in Myrmecological News, Gora et. al. reported on their investigation into swimming by the carpenter ant, Camponotus pennsylvanicus. They found carpenter ants use vision to find escape platforms from the water. One hundred percent of the control ants placed in the water of the test apparatus were able to swim to the edge and get out of the water successfully. Ants with their vision occluded, on the other hand, failed to exit the water.

Although this study focused on ants swimming as a method to escape from water if they fall in accidentally, some Camponotus ants in pitcher plants are able to actively swim to capture mosquito pupae for food. In this video you can see how they move all six of their relatively short legs to push through the liquid.

As you might expect, ants that live in areas that are regularly flooded by tides, such as ants living in mangrove swamps, are particularly good at swimming.

This video from Life in the Undergrowth shows mangrove ants running across shallow water and then at about 1:02 minutes actively swimming in the water. Notice how the swimming ant holds its hind legs out behind it like a rudder.

Yanoviak and Frederick tested 35 species of tropical forest ants to see how many had the ability to move through water in a directed way. Of those, ten species were able to show rapid directed movements and ten more exhibited slower, but directed movements. The remaining species apparently needed tiny life jackets.

The bottom line is that although different species of ants vary in their ability to swim, some are quite adept at it.

Previous Posts at Wild About Ants:

References:

Gora, E.M., Gripshover, N. & Yanoviak, S.P. (2016) Orientation at the water surface by the carpenter ant Camponotus pennsylvanicus (De Geer, 1773) (Hymenoptera: Formicidae)  Myrmecol. News 23: 33-39. (Let me know if the link doesn't work and I'll find it for you.)

S. P. Yanoviak, D. N. Frederick (2014) Water surface locomotion in tropical canopy ants. Journal of Experimental Biology 217: 2163-2170; doi: 10.1242/jeb.101600

Today let's take a look at Animal Weapons: The Evolution of Battle by Douglas J. Emlen and illustrated by David J. Tuss

As I clicked on the category "ant books" for this post I realized that is a bit of a stretch. Ants are mentioned on a few pages, but the author doesn't talk about much more than worker ants with big jaws. He actually does most of his research on beetles. That said, he does cover the weapons of the entire animal kingdom. His editors even convinced him to tackle human weapons, although he admits being reluctant to do so.

You can see what the author has to say about his book in this video from American Scientist.

 

Emlen's writing is clear and engaging. He has been able to make some conclusions based on patterns he has seen in the natural world. His observations about cheaters in the world of battle are particularly chilling.

 Animal Weapons: The Evolution of Battle has elements that are likely to appeal to both those interested in natural history and those interested in weaponry and battle. Definitely recommended.

If you have time, you might want to watch the SciShow Talk Show: Animal Weapons with Doug Emlen & A Southern Three-Banded Armadillo,

plus SciShow Talk Show: More about Animal Weapons with Doug Emlen & Professor Claw the Emperor Scorpion.

Have you read this book? What did you think of it?

Paperback: 288 pages
Publisher: Picador; Reprint edition (December 1, 2015)
ISBN-10: 1250075319
ISBN-13: 978-1250075314

Disclosures: This book is my personal copy. Also, I am an affiliate with Amazon so I can provide you with cover images and links to more information about books and products. As you probably are aware, if you click through the highlighted title link and purchase a product, I will receive a very small commission, at not extra cost to you. Any proceeds help defray the costs of hosting and maintaining this website.

It has been too long since I've posted here, so let's jump in with two discussions about battles and weaponry in the insect world. Today we'll look at battles among acacia ants. Tomorrow let's take a look at animal weapons in general.

Acacia ants, Crematogaster mimosae, live on and fiercely defend Africa's whistling thorn acacia trees, Acacia drepanolobium.

Crematogaster_mimosae_casent0904507_p_1_highCrematogaster mimosae photograph by Will Ericson / © AntWeb.orgCC-BY-SA-3.0

Scientists have found they can induce battles between ant colonies on separate trees by bringing the branches of the trees into contact. The worker ants begin to fiercely defend their home tree when overlap occurs. The ants both bite and release a venom. When in defensive mode, Crematogaster ants hold their metasomas over their backs in a characteristic way, which has given them the common name "acrobat ants." Unlike some ants that have more ritualistic confrontations, Acacia ants actually battle causing significant losses in the number of workers. Before one colony is completely wiped out, however, the battle ceases and one colony is the apparent winner.

Recently Kathleen P. Rudolph and Jay P. McEntee studied Crematogaster mimosae colony battles in Kenya. They examined the genetic makeup of workers of the colony before and after the battles and discovered the winning colony became more genetically diverse afterwards. In other words, worker ants from the losing colony were joining forces with those of the winning colony. In fact, when two colonies fought to a draw, they actually ended up fusing together, including their queens.

From an ant biology conventional wisdom, this is startling finding because it is generally thought ant colonies reject workers that are not their sisters. However, the fact that even the winning colony is weakened and can't defend the trees against large herbivores makes the ability to recruit workers from a losing colony a distinct advantage.

Of course, there are ants that raid other colonies for pupae. Other ants eat the bodies of their fallen victims. Do you know of any other ant species that recruit or allow the losing workers to join the colony?

Literature:

Kathleen P. Rudolph, Jay P. McEntee. Spoils of war and peace: enemy adoption and queen-right colony fusion follow costly intraspecific conflict in acacia ants. Behavioral Ecology, 2015

Mack, Aileen. "Turn mortal enemies into allies? Ants can. UF News. 17 March 2016. .

People have long been interested in morphological and behavioral differences between different worker castes in ants.

Camponotus_floridanus-head_1

(Photograph of a head of a major worker of Camponotus floridanus by April Nobile / ©AntWeb.org / CC-BY-SA-3.0, retrieved from Wikimedia)

A recent study published in Science teases apart some of the proximate mechanisms controlling foraging behavior in the Florida carpenter ant, Camponotus floridanus. Particularly, it focuses on the environmental factors that control genes by switching them on and off, an area of study called epigenetics. The study authors found that minor workers foraged much earlier in their lives than major workers, but by injecting major worker ant brains with compounds that reduced histone acetylation, they were able to stimulate foraging behavior in younger major ants.

This video summarizes parts of the study.

What do you think about the few blips in the video, such as the narration talks about foraging over the image of a minor worker carrying a pupa (brood tending?), as well as the first, slightly shaky definition of epigenetics?

What do you think of this study?

 

References

Sindya N. Bhanoo, Ants Can Change Their Roles, Study Finds New York Times, Dec. 31, 2015. (A version of this article appears in print on January 5, 2016, on page D2 of the New York edition with the headline: Insects: Chemicals Can Turn an Ant Society on Its Head.)

Daniel F. Simola, et al. Epigenetic (re)programming of caste-specific behavior in the ant Camponotus floridanus, Science  01 Jan 2016: Vol. 351, Issue 6268.
DOI: 10.1126/science.aac6633