Dogwood Flower Community

Sometimes we get so used to seeing ants visiting extrafloral nectaries, it seems unexpected to see them visiting regular floral nectaries.


Take this shrubby dogwood flower (probably gray dogwood, Cornus racemosa). The nectaries are the creamy yellow bands at the base of the female part of the flower (the pistil or carpel) in the center.



Formica workers seemed to be visiting the plants most frequently, although other ants were in the area.


Ants weren’t the only insects attracted to the nectaries of the dogwood flowers.


Along with the usual wasps, flies and bees, there were also more unusual true bugs and beetles.


A number of the smaller butterflies stopped by, including hairstreaks and blues.

It turns out azure butterflies in particular are attracted to these types of dogwoods and lay their eggs on them. What happens next? Of course, the ants tend the azure caterpillars! Nature Posts blog has an incredible series of photographs and videos of ants tending azure butterfly caterpillars.

Interested in planting a garden for ants or butterflies? You might want to consider planting some of the dogwoods (Cornus sp.)

Have you ever seen azure caterpillars on dogwoods? I am definitely going to be looking from now on.


Extrafloral Nectaries on Luffa Leaves

Did you recognize the big yellow flower from the Wordless Wednesday post with the carpenter bee? This might give you a hint:

It was from a luffa or sponge gourd, Luffa aegyptiaca (previously named L. cylindrica.)

Why were the ants on the underside of the flower in the last photograph of that post? It turns out that the luffa plant has been crawling with rover ants, even before it started to flower.

For a clue, let’s look at the underside of the luffa leaves. What are those green bumps on the leaf surface between the veins?

You might wonder if they are the leaf openings called stomata, but the stomata are the smaller dots.

Close up the bumps look like tiny green volcanoes.

Those are extrafloral nectaries, or EFNs. Extrafloral nectaries are nectar-producing glands found in areas of the plant outside of the flowers. Extrafloral nectaries occur in at least 66 different plant species and vary in size, shape and placement. The type of found in luffa are called “button-shaped.”

Like the nectar produced in the floral nectaries, extrafloral nectar is a liquid solution of sugar in water, with trace amounts of amino acids. The nectar attracts many different kinds of insects, but ants are often the most common visitors. The ants often chase away or capture plant-feeding insects, thus protecting the plant.

This means we can add luffas to the list of plants that might be useful for gardening for ants.

For more information, see:

Vivek Mohan Agarwal and Neelkamal Rastogi. 2010. Ants as dominant insect visitors of the extrafloral nectaries of sponge gourd plant, Luffa cylindrica (L.) (Cucurbitaceae). Asian Myrmecology, 3, 45–54. (free .pdf available at the “Read full PDF” link after the abstract.)

Have you seen the journal Asian Myrmecology? Currently the articles are offered for free online at the website.

Sandmat and Ants: Pollination?

It is spring and the flowers are blooming in Arizona.

Do you recognize the plants? I believe they are smallseed sandmat, Chamaesyce polycarpa.

In any case, ants were all over them.

On the day I visited, Dorymyrmrex bicolor workers were everywhere. Getting a little closer…

I could see the front of the ant’s head was covered with pollen.

Two more workers, with equally yellow mandibles.

The Dorymyrmex workers were definitely visiting the flowers* (see below).

I also saw Pogonomyrmex californicus workers in the sandmat.

They weren’t visiting the “flowers,” though.

The Pogonomyrmex workers were searching under the plants. I saw a lot of gasters in the air. Perhaps they were searching for seeds? I also wondered if there were extrafloral nectaries under the leaves or on the stems that were attracting the ants.

Frankly, I wasn’t that familiar with these little plants, so I wasn’t sure where the nectaries were.

Upon investigation, it turns out that what look like *flowers* are actually special flowering structures unique to euphorbs called cyathia (singular cyathium). What look like anthers are actually male flowers and at the center is a female flower. The dark reddish areas near the center are the nectar glands within the cyathia. (For more details about the flowering structures see Wayne’s Word (scroll to absolute bottom of post) or the flower structure of euphorbs.)

In any case, it seems like this plant would be a great one to add to an ant garden. I’m looking forward to learning more about it’s life cycle and how ants interact with it.

What do you think?

Gardening For Ants? Yes, You Can!

This is an idea that is probably well ahead of its time, but after writing about how you can plant a garden to encourage bees last week, I decided to figure out if you can plant a garden to encourage ants. I think the answer is, “Yes!” and if you are interested in ants, you’ve probably already been doing some of these things.

What do you need to provide to encourage ants in the garden? The same things you would provide for butterflies or bees:  food, water and shelter.

1. Plants with extrafloral nectaries provide food and water for ants

Bees collect pollen and nectar from flowers, which is why they are great pollinators. Ants also have relationships with plants, but it often much more subtle. Many plants have nectaries, which are glands that produce sweet fluid fluids, outside of those that reside in the flowers. These nectaries, called extrafloral nectaries or EFN’s, are often used almost exclusively by ants. They supply both water and nutrients.

You are probably already familiar with one well-known example of extrafloral nectaries in the popular landscape plant, the peony. Ever see ants crawling all over peony buds right before the blossom opens?

Peonies have very small extrafloral nectaries along the outside edges of the flat, leaf-like scales of the flower buds. The nectaries provide a mixture of sugars, water and amino acids that attracts hordes of ants. In exchange the ants chase off or eat herbivores that might attack the bud. They also protect the peony “fruit.”

Sunflowers are another example. They have big showy flowers that attract bees.

If you look on the stems, however, you are likely to find ants. The ants are visiting extrafloral nectaries for food. (see another post about ants on sunflowers)

Over 70 different families, from buttercups to violets have extrafloral nectaries. The nectaries may be dripping nectar during definite seasons of the plants’ life cycle, for example for a week or so while the plant is blossoming, or may be available year round.

Here in the Southwest, many cacti have extrafloral nectaries.

It is thought that ants provide various services in exchange for the free meal. (For more information, try these posts about other plants with nectaries:   red bird of paradise, vetch, spurges)

2. Providing food- aphids or scale insects

Now you’ll think I’ve gone over the deep end, but if you are serious about gardening for ants you might want to provide some plants that are hosts to aphids or scale insects.

Leaving a few weeds that are prone to aphids doesn’t necessarily mean your garden will be infested, because some aphids are specific to only one or a few plants. An example is the thistle aphid, Brachycaudus cardui.

Ants definitely benefit from the honeydew the aphids secrete, as do a number of other insects and even birds. You may also benefit, because it is easy to spend hours studying the complex relationships involved.

3. Providing shelter for ants

Can you provide shelter for ants? It might be more simple than you realize. You just need to have a few of these:

Well, maybe not so artistically arranged.

A few flat rocks strewn about your garden are likely to provide a valuable resource for ants. In the cooler parts of the year, ants use rocks that are warmed by the sun as incubators for the larvae. In fact, these particular rocks have a colony of rover ants under them doing just that this week.

4. Get to know your local ants

One of the best ways to develop an ant-friendly garden is to find out what species are found in your area and what their requirements are. Find out which species are keystone species important to your local ecology and which are introduced pests that should be discouraged. You are likely to be a pioneer, so keep records and share what you find out.

Looking back, it seems like gardening for ants could be a real possibility. In fact, if you know of a publisher who might be interested, I would be willing to write up a guide. I can guarantee it would be one of a kind 🙂

Now, you may ask, “Why on earth would you want to encourage ants?”  More about that next…