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The Fire Ants: Chapters 7-9

Anyone ready to discuss chapters 7-9, plus the Interlude, Mundane Methods? (For those of you jumping in late, we are discussing The Fire Ants by Dr. Walter Tschinkel by going over a few chapters per week. Click "The Fire Ants Book Discussion" category for related posts.)

Chapter 7 is about the fire ant nest. The construction and shape of the fire ant nest varies with a number of factors, including season, soil type and weather.

In general, a founding colony starts out with a simple tunnel, and as the number of workers increases, the number of underground tunnels and chambers increases. Solenopsis invicta colonies dump the excavated soil onto the surface, forming a dome-shaped mound. Unlike many other ants, they actually build tunnels in the mound and utilize it, especially during the winter months.

Below is a photograph of a zinc cast of a Solenopsis invicta nest within the above ground mound of soil. This is a negative impression, meaning the space of the tunnels has been filed with zinc and the surrounding soil has been removed.

Do you think that this use of the excavated soil comes from the fact Solenopsis invicta is from an area that floods frequently?

Anyone have comments about this chapter or the Interlude, There's Nothing Like Getting Plastered? Tschinkel is well known for his casts of various ant nests. What do you think of his idea that we need to learn more about the nest structure or architecture as a way of understanding social insects?

Edit:

And I just found a video of this:

Chapter 8. Looking at fire ant territories.

In addition to the nest itself, most ants also occupy an area around their nest that is used for foraging. This forms a territory, from which ants from other colonies are typically excluded. The size of the territory is usually dependent on the size of the colony (number of workers), as well as presence of neighboring colonies. Interestingly, fire ants have extensive underground foraging trails throughout their territories

This chapter is especially useful because it discusses the methods used to study territoriality in ants.

What do you think? I am still mulling the relationship of nest tunnels to underground foraging tunnels.

Chapter 9. What fire ants eat.

Like many other ant species, Solenopsis invicta workers are predators of arthropods, scavengers and exploit whatever sweet liquids are available within their territory. We already talked a bit about whether fire ants tend aphids. Tschinkel suggests that the ants exploit extrafloral nectaries and root-feeding homoptera for sugars.

(If you were wondering about fire ants and vertebrates, Tschinkel saves that for chapter 36.)

According to a study by Tennant and Porter (1991), fire ants carry liquid food back to the nest about 80% of the time.

We tend to think of ants storing food in their social stomach, the crop, but Tschinkel reminds us that ants can also store excess food as fat, the typical animal food storage molecule, glycogen, and also as storage proteins, such as hexamerins.

Anything surprise you in this chapter?

Interlude:  Mundane Methods

Okay, I admit it. I loved this part. It made me laugh out loud, especially the part about ant hotels on page 132. Who hasn't had their ant workers decide to move into another laboratory/building/office on a whim?

Do you have any ant wrangling tips to share?

So, how are you doing? Are you ready to move on the read Chapters 10-12, about the founding of new colonies? Or has everyone gotten too busy and/or lost interest? (I have to admit I have been distracted a bit by Army Ant Week over at Myrmecos.)

Reference:

Tennant, L.E. and S.D. Porter. 1991. Comparison of diets of two fire ants species (Hymenoptera:  Formicidae): Solid and liquid components. Journal of Entomological Science. 26:  450-465.

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