Category: Ant Facts

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Ants and Salt

When my very good friend Deb Sparrow sent me this photograph of a harvester ant collecting a piece of a blue corn chip that had fallen from her lunch, I immediately took it at face value. A harvester ant carrying a corn chip seems like an obvious combination. After some research, however, I am beginning to wonder whether the ant was also interested in another, not so obvious, aspect of the corn chip.

ant-blue-corn-chip
Photograph by Deb Sparrow (near the Hassayampa River in Arizona)

Recent research has shown that certain ants collect salt (sodium chloride). Michael Kaspari, Stephen P. Yanoviak, and Robert Dudley presented different species of ants baits with varying concentrations of salt (NaCl) versus two concentrations of the standard bait attractant, sucrose solution in water.

The scientists found the ants responded to the salt solutions depending on their distance from the ocean. Ants near the ocean presumably would have more salt available, carried to the land by wind and storms. In general, the further from the shore, the more the salt solution attracted ants and the steeper the dose response.

One interesting exception, however, were ants that generally are thought of as carnivorous, for example fire ants of the genus Solenopsis. The idea is that carnivorous ants get their salt through their prey, whereas vegetarian species, like the harvester ant above, would need to supplement their diet. The researchers also found that ants of the genus Pheidole did not respond to salt. The diets of many Pheidole are not well-studied, but at least a portion are also seed harvesters.

Guess I’ll be paying more attention to ants and salt from now on. I have to say that here in Arizona our water, and thus irrigated soil, is full of salts. In fact one of our main rivers, the Salt River, is named for the natural salt springs that feed it. Maybe our natural abundance of salt is one of the reasons why we have such a variety of ants.

What do you think of ants and salt?

References:

On the biogeography of salt limitation: A study of ant communities by
Michael Kaspari, Stephen P. Yanoviak, and Robert Dudley.
Proc Natl Acad Sci U S A. 2008 November 18; 105(46): 17848–17851.

Ants More Attracted to Salt Than to Sugar by James Parker for The Daily Californian

The biogeography of sodium limitation by Dr. Michael E. Kaspari at The AntLab. Also see link to pdfs of his papers.

Inland Ants Crave Salt, and Hurricanes May Help by John Roach for National Geographic News

Edit:  The Circus of the Spineless is now up at Greg Laden’s Blog

CoSButton1

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Extrafloral Nectaries and Ants

You get to see a lot of surprising things in the Sonoran Desert of the southwestern United States. How cacti provide nectar for ants is just one example.

Most of us learned in school that flowers produce nectar, which is then collected by bees, butterflies, bats and/or moths. Extrafloral nectaries are structures on a plant that produce nectar, but they are not inside flowers. They may be located on petioles, leaves, sepals, or stems.

Extrafloral nectaries are more common than you would think. Extrafloral nectaries are found in a wide range of different plants from over 70 different families, from buttercups to violets. The primary visitors to all these extrafloral nectaries are ants.

Believe it or not, extrafloral nectaries are present in many cacti. Cacti have many specializations for saving water, and even have a different system of photosynthesis that is more water efficient.

barrel-cactus
This barrel cactus is not spineless (for the Circus of the Spineless folks).

Yet, certain species of cacti also have tiny extrafloral nectaries within patches of spines, known as thorn nectaries, which may literally drip nectar. The plant is losing water (albeit probably in very small amounts), to in attract ants. The orangish, waxy bumps in the following photo are the nectaries.

extrafloral-nectary-cactus1

Why?

No one knows for sure why the cacti have extrafloral nectaries, and it is likely that different kinds of cacti have them for different reasons. Scientists have proposed that some cacti supply nectar to ants to keep them away from the flowers, where the ants might drive away pollinators. This seems unlikely since the extrafloral nectaries are active throughout the year or at different times of the year, not just when flowers are open. The cacti may supply nectar to keep the ants away from tending aphids, scales or mealybugs that might cause more problems for the plant, although ants don’t seem to tend some of the most prominent cactus-feeding species. The cacti may supply nectar to lure ants into the area because the ants’ activity improves the texture and/or nutritional value of the soil immediately around the cacti. This last idea makes a lot of sense given desert soils are often low in organic matter and nutrients, and ants are known to improve soil. Also, ants may provide a cleaning service, keeping down disease-causing fungal spores and bacteria, as well as chasing away or eating disease-carrying pests.

Ants may chase away seed-feeding bugs like these. On barrel cacti the nectaries are active when the plant has fruit, and the seed-feeding bugs are around. Can you see the ant and extrafloral nectary in the middle, between the fruit?

cactus-bugs

Not only do a variety of native ants take nectar from cacti, but introduced species may as well.

extrafloral-nectary-cactus3

These tiny introduced Brachymyrmex gather nectar of the extrafloral nectaries of another barrel cactus. Do they perform the same duties as the native ants? Since we don’t know exactly what the ants are doing in most cases, it is hard to know for sure.

Have you ever seen ants visiting extrafloral nectaries? What do you think?

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Vegetarian Spider Eats Food Meant for Ants

Maybe Miss Spider’s eating habits aren’t so out of line after all. In the children’s books, Miss Spider eats only flowers, which in the past seemed unlikely because spiders were all thought to be carnivores. Now scientists have found a vegetarian spider. This spider is sneaky, however, because it eats food provided by plants that was intended for ants.

Acacia trees from Central and South America have a special relationship with acacia ants. Simplistically, the plant provides food and a place to live in the swollen thorns, and in return the acacia ants ward off animals that might eat the plant. The ants also remove competing vines.

beltian-bodies-bullhorn-acacia

Do you see the yellow structures on the tips of the leaves of this bullthorn acacia? Those are called Beltian bodies and they are loaded with protein. Normally ants take the Beltian bodies to feed to their larvae.

Recently researchers have found a jumping spider that takes advantage of the relationship and steals the Beltian bodies to eat for itself. Tricky spider!

References:
Herbivory in a spider through exploitation of an ant–plant mutualism
Christopher J. Meehan, Eric J. Olson, Matthew W. Reudink, T. Kurt Kyser, Robert L. Curry
13 October 2009 Current Biology
19(19) pp. R892 – R893

Veggie spider shuns meat diet at the BBC

Nice picture of spider at NPR

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Ant Fact or Fiction Quiz

How well do you know ants? Answer the following questions by selecting true or false. Better yet, stump your family and friends by giving them the quiz. When you are done, you can find the answers below the photograph.

1. Some ants can explode when threatened by enemies, true or false?

2. Peony plants require ants for their buds to open into flowers, true or false?

3. All species of ants can sting, true or false?

4. Soldier ants are all males, true or false?

5. Ants can be used as stitches to close wounds, true or false?

6. Ants are silent, true or false?

7. Ants plow more soil than earthworms, true or false?

8. Scientists who study ants are called antomologists, true or false?

9. Certain types of caterpillars eat ants, true or false?

10. Ants plant the seeds of many wildflowers, including violets, true or false?

11. Ants pollinate many types of flowers, true or false?

12. Ant larvae can make silk, true or false?

yellow-ant

Ant Quiz Answers

1. Some ants can explode when threatened by enemies, true or false?

True: The soldier ants of the carpenter ant Camponotus saundersi swell up and explode all over their enemies.

Reference: Exploding Ants by Joanne Settel

(Affiliate Link to Amazon)

2. Peony plants require ants for their buds to open into flowers, true or false?

False: Although this is a common myth, the truth is that if you keep ants off the peonies by spreading sticky substances on the stems, the peonies will still open. The actual relationship is that the peony buds supply nectar to the ants and in return the ants keep off pests like caterpillars.

3. All species of ants can sting, true or false?

False: Many species of ants lack stingers. They may spray formic acid or bite (or explode) to defend themselves, rather than actually sting.

See the bite or sting post for more information.

4. Soldier ants are all males, true or false?

False: All worker ants are technically females and because soldiers are specialized workers, they are females. The only males are wasp-like forms that have wings and do now work inside the nest.

5. Ants can be used as stitches to close wounds, true or false?

True: Certain species of army ants with large jaws have been used as stitches or sutures to close wounds. The soldier ant is enticed to bite across the wound and it clamps down, closing its jaws.

6. Ants are silent, true or false?

False: As scientists develop more and more sensitive equipment to record sounds, we are finding that many types of ants actually make a lot of noise. For example, R. Hickling has some recordings of fire ants squeaking (stridulating). Even more interesting, certain caterpillars make sounds to attract and communicate with ants.

7. Ants plow more soil than earthworms, true or false?

True! Surprised? Ants nest in the ground and improve the soil by tunneling and adding nutrients. Earthworms were introduced to eastern North America by the early European colonists. They did not exist here before that.

8. Scientists who study ants are called antomologists, true or false?

False. Scientists who study insects are called entomologists. Specialists who study ants are called myrmecologists, coming from the Greek word for ant. The Latin word for ant is Formica.

9. Certain types of caterpillars eat ants, true or false?

True! Caterpillars of some butterflies, particularly blues, have complex relationships with ants and spend time in the ant nests feeding on ant larvae.

10. Ants plant the seeds of many wildflowers, including violets, true or false?

True. Ants carry seeds around and drop them in their waste piles, which is an ideal place for seeds to grow. In fact scientists have shown there are far fewer wildflowers where ants are absent.

11. Ants pollinate many types of flowers, true or false?

False: Ants are not very good pollinators, although there are a few very specialized flowers that rely on ant pollinators.

12. Ant larvae can make silk, true or false?

True: Ant larvae produce silk with glands in their mouths. Many species spin silk bags around themselves, called cocoons, when they are ready to pupate and change into adult ants.

Hope you had fun!