Bug of the Week: Thurber’s Cotton and Ants

Yesterday we introduced the lovely plant, Thurber’s cotton, Gossypium thurberi.

While I was taking photographs of the plant, I noticed some ants.

ant-on-flower-petal-2These kind of ants are called rover ants. They are not very big. What are they doing on the plant?

ant-visiting-floral-nectaryHere’s one in the flower. It is visiting the nectar-producing area or “floral nectary.”

ants-at-EFNs-darkThe rover ants were also visiting an area under the flowers, on the sepals. Any ideas why?

ant-visiting-EFN-33Having some experience with cotton plants, I  realized the ants were visiting some nectar-producing areas there as well. Nectaries outside the flower proper are called “extrafloral nectaries.” See that dimpled area the ant is facing? That is an extrafloral nectary.

ants-at-EFN-multipleAs you can see, the extrafloral nectaries on the plant were very popular.

Many different plants produce nectar in various extrafloral nectaries and most of them attract ants and small wasps.

The most commonly-reported reason that plants have these structures is that the nectaries attract predators and parasites, which in turn attack the eggs and larvae of plant-feeding insects they encounter.

Have you ever seen ants visiting nectaries on plants? What kind of plant was it?

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Mystery Seed of the Week On Sabbatical

After 220 mystery seeds, it is time to step back and evaluate where we want to go from here. Although seeds are incredibly beautiful and fascinating, frankly it is becoming increasingly difficult to gather new material each week. Therefore, Seed of the Week will be taking a brief sabbatical.

Some options for the future are:

  1. Posting plant-based lessons and activities for kids instead, getting back to our children’s science roots.
  2. Developing a website with all the mystery seeds as thumbnails and links to the answer posts, perhaps arranged via plant families to make it more accessible and useful.
  3. Continue on  posting mystery seeds as before after gathering more materials
  4. Develop collaborations with others interested in botany/gardening/plants to expand into new projects.

Obviously, none of these ideas are mutually exclusive.

If you have any suggestions for what would be useful additions to this series, ideas for collaborations, or have comments about the different options, your input would be greatly appreciated.


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Seed of the Week: Thurber’s Cotton

Our mystery seeds in the “pod” were from a lovely plant called Thurber’s cotton, Gossypium thurberi.


If allowed to reach its full potential, Thurber’s cotton is a large shrub or small tree, reaching up to 15 feet tall. It is native to Arizona, and is also called Arizona or desert cotton.


Although I called it a pod not to give away the answer, this structure is actually a “boll.” If you look closely, you can see the white fuzz of “cotton” around the seeds. There usually isn’t enough fiber to bother trying to harvest it, though.


Thurber’s cotton plants have palmate leaves, mostly with three lobes. The leaves fall off in the winter.


The best part about the plant are the delicate, cupped flowers with a hint of pink.

Have you ever seen cotton growing? How does this plant compare?

Interested in finding out more?

Firefly Forest has more photographs

Check out Bug of the Week tomorrow for more about this plant.

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