The Consult-ant

There's a question for the Consult-Ant this week. (The “Consult-Ant” started on the Leaping from the Box website, where I answered questions about ants and ant farms. From now on I will post the answers here, and when Karen has time she will also post the answers on her site.)

Question:

This comes from Ol Donyo Orok Hill in Southern Kenya (on the border with Tanzania) at an altitude of around 4500 feet.  I found these ants all dead at the entrance of a hole (what I assumed to be their nest).  This was far enough away from any human habitation, farming, or other activity (other than some goat herding) that I ruled out the use of insecticide.  There were a few more dead, spread out of the the space of about 1 square foot, but the attached photo shows the vast majority of them in a small, dense pile.  Some of their exoskeletons were coming apart (especially the tips of the abdomens), but it didn't look like ruptures from predation, rather just decay.

The stem of the plant in the photo is Solanum incanum (Poison/Sodom Apple), which is both indigenous to the area and poisonous to humans and domestic stock, but I doubt that ants would eat something familiar to them which if it was poisonous.  I don't know what species of ant they are, but the closest I can get is some Pachycondyla sp. (though I'm really not sure).

Do you know what may have caused this seemingly sudden mass die-off?

Answer:

Taking a look at Ants of Africa for ants in the genus Pachychondyla, your identification seems in the right ballpark. Are there any experts out there who can tell us more about what kind of ants these are?

As for what has happened, when I've seen similar piles after a couple of events. Most commonly, either the ant colony had a battle with a neighboring colony or there has been some adverse weather that has caused a mass die off.

If the battle was with a neighboring colony of ants, not all the causalities will be torn apart, particularly if the damage was caused by stings or chemical weapons.

Flooding of portions of the nest during heavy rains can also cause big die offs in species that nest underground.

Readers:  Do you have any suggestions why these ants might have died?

Please leave your thoughts in the comments.

4 Comments

A reader has a problem identifying his honeypot ant queens. Anyone out there good at Myrmecocystus identification? See the links for his photographs.

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I have an ant question! (With photo links!)

Hello there!
I recently captured a few queen ants during their nuptial flight this past August and I would like to know what species of ant this ant belongs to.

A little background information. I live in the Mojave desert, in the most Southern part. I am at an elevation of about 4,000ft and in the transition habitat between pinyon/juniper and pine. The workers are yellow/orange and are nocturnal. I’ve seen these ants feeding on nectar and small insects. Their nuptial flight took place at dusk after an afternoon thunderstorm.

Anyways, I think this species is a Myrmecocystus mexicanus, but a few others have mentioned that they are either M.testaceus or M.navajo. I’m so confused because all three sub species look the same! Here are links to two photos. Any information will be greatly appreciated! Thanks.

http://i344.photobucket.com/albums/p330/jimbodw07_2008/DSC_0001.jpg

http://i344.photobucket.com/albums/p330/jimbodw07_2008/96640104.jpg

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My suggestions:

As we discussed, you might want to wait until the workers come out.

If you have a good microscope and some knowledge of ant anatomy, AntWiki has a key to Myrmecocystus, to species level (both queens and workers), as well as general information about the genus

Some other useful links:

Navajo Nature has taxonomic information for Myrmecocystus

Alex Wild has photographs of various species

BugGuide has some photographs of Myrmecocystus queens, too

Does anyone else have any other suggestions? If so, please let leave a comment or contact me via wildaboutants (at) gmail.com. We'd appreciate it.

honeypots-hanging
Honeypot ants have a replete caste for storing food.

 

 

2 Comments

We have a question for the Consult-Ant* this week.

I have an ant question.
 
I was curious about ant eyesight. Not about their color vision but more specifically their quality of vision in the dark. Is it better or worse than a human's night vision?

This is a great question!

The first thing to remember about ants is that they perceive the world in vastly different ways then we humans do. They produce a number of different chemicals and communicate in ways that we can only dimly appreciate. Let's not forget, some ants are completely blind and they get around just fine.

That said, ants do usually live in dark tunnels, either underground or in wood. Many species forage at night, either all the time or during certain seasons. They are able to find their way around in the dark.

camponotus-festinatus1

For example, this carpenter ant lives in the hot desert. It forages at night and is rarely seen during the day.

To study how ants see at night, scientists have been looking closely that the anatomy of  the eyes of ants.

This figure from Invertebrate Vision, edited by Eric Warrant, Dan-Eric Nilsson shows that dark-adapted eyes of invertebrates are structurally different from light-adapted ones.

 

Ajay Narendra and his colleagues (2011) have been studying Australian bull ants (Narendra has photographs of bull ants ) that are active at night and comparing them to day-active species. They found that ants that were active at night had different eye measurements and eye structures, both within a given species (that is active both during the day and night) and between related species. The eye area, facet size, and ocelli (the smaller simple eyes at the top of the head) size, etc. were larger in night-active ants.  Reid et al. discusses more specific information about how the ants use their specialized eyes to see polarized light and landmarks during navigation at night.

Have I danced around your original question long enough? Comparing humans to ants is difficult because in a lot of ways it is comparing apples to oranges, plus our understanding of what other animals perceive is limited. Nevertheless, I'm going out on a limb. All these structural differences suggest that certain ants can be quite specialized for night vision. Based on that evidence, it would seem that ants are probably just as capable, if not more capable of night vision than unassisted humans. Of course humans are capable of inventing and using sophisticated devices to assist our night vision. In that case, humans win hands down.

What do you think about night vision in ants?

For more information:

Ajay Narendra, Samuel F. Reid, Birgit Greiner, Richard A. Peters, Jan M. Hemmi, Willi A. Ribi and Jochen Zeil.  (2011) Caste-specific visual adaptations to distinct daily activity schedules in Australian Myrmecia ants. Proc. R. Soc. B.  278:  1141-1149. (free .pdf available)

Reid, S.F., A. Narendra, J.M. Hemmi and J. Zeil. (2011). Polarised skylight and the landmark panorama provide night-active bull ants with compass information during route following. The Journal of Experimental Biology. 214: 363-370. (free .pdf available)

Wild About Ants post about color vision in ants

 

(* As I mentioned previously, I have been the “Consult-Ant” on the Leaping from the Box website. I answer questions about ants and ant farms. From now on I will post the answers here, and when Karen has time she will also post the answers on her site.)

4 Comments

We have a question for the Consult-Ant today:

Hello

I have an ant question!

Over the years I have seen an unusual type of ant mound. It is a long, linear "mound"; actually a series of small mounds connected by tunnels of soil particles. The unusual thing about them is that extend in a straight line for several feet. Somewhere I heard these called "railroad ants", but I don't know if that is more than just a local name or description of the straight-as-a-string nest mound. I'd appreciate any information you might have about them, like scientific name or a reference where I could learn more. Thanks.

Dale

Dale,

Since you don't tell me where you are from, I'm going to take a wild guess and suggest you might possibly be talking about a type of fire ant. Fire ants tend to build loose mounds that are sometimes long and narrow. (Except if they were fire ants, you'd probably know about them already).

Does the mound you are seeing look like the second photograph in this post?

If not, please let me know where you are located, which will help me narrow the choices. Also, roughly how big are the structures?

Anyone out there heard this common name and know more about it? Please let us know if you have some ideas.

(Note: As I mentioned previously, I have been the “Consult-Ant” on the Leaping from the Box website. I answer questions about ants and ant farms. From now on I will post the answers here, and when Karen has time she will also post the answers on her site.)