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?

Seed Cache

The ants are still active here, but I haven’t had much to report. In an effort to get back in the swing of things, I will be posting some short notes.

Do you know what this is? I tipped over a rock near a Southern fire ant nest and found this cache of tiny seeds. It is easy to forget that fire ants also harvest seeds.

I should have picked up a couple of the seeds to try to sprout them. It wasn’t obvious where they came from, as there weren’t any plants nearby.

Have you ever found seed caches in fire ant nests?

Nectaries on Red Bird of Paradise

The red bird of paradise, Caesalpinia pulcherrima, is a plant with large, attractive red-orange-yellow flowers. It is a popular plant in desert landscapes.

The flowers have long stamens, and is thought to be pollinated by butterflies, especially swallowtails that flutter their wings while feeding.

This flower also has an ant.

Can you see it now?

It’s a rover ant, Brachymyrmex patagonicus. Any ideas what the ant might be doing?

The swollen gaster might be a clue.

Honey bees and wasps exhibit the same behavior.

Here’s another clue.

Apparently these plants have extrafloral nectaries as well as nectaries within the flowers. Isn’t it funny where all these extrafloral nectaries show up on desert-adapted plants?

R. W. Cruden and Sharon M. Hermann-Parker. 1979. Butterfly Pollination of Caesalpinia Pulcherrima, with Observations on a Psychophilous Syndrome. Journal of Ecology. 67( 1): 155-168