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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.)

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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.)

Recently a follower on our FaceBook page asked an interesting question,  "Will ants die if they eat chocolate?"

The question is an intriguing one. As many of you probably already know, consuming chocolate can be fatal to dogs and cats. A friend of mine recently had to rush her dog to the vet because he ate most of a large cake with chocolate in it.

The compound that is toxic to dogs and cats is an alkaloid called theobromine. Chocolate also contains small amounts of another, related alkaloid: caffeine. In fact, theobromine is a chemical precursor to making caffeine in plants. (Some of the older literature suggests chocolate does not contain caffeine, but newer, more sophisticated chemical tests have shown that caffeine is indeed present in chocolate). See the Hershey website for a discussion of theobromine and caffeine in chocolate.

Caffeine is known to kill insects. Nathanson (1984) suggested that it was a naturally occurring pesticide, and showed that it can inhibit growth in tomato hornworm larvae. More recently, scientists have been looking at genetically modifying tobacco plants to make caffeine. Their thinking is that the caffeine would repel or kill insects that feed on the tobacco. In their experiments, the caterpillars of the tobacco cutworm and small white avoided eating plants treated with caffeine. It was a repellent (Kim, et al.).

What about in ants?

As personal experience, I had once used a chocolate-covered peanut butter candy as a bait for some ants.

The sidewalk ants seem to prefer the peanut butter, although possibly a couple are trying the chocolate. It isn't clear.

This fire ant also seems to be feeding on the peanut butter part. This highly-limited evidence might suggest ants might also be repelled by certain ingredients in chocolate.

Miyashira, et. al. recently looked at the effect of caffeine on leaf-cutter ants. They found that although there was "no conclusive effect" on the ants, the higher doses of caffeine did kill the mutualistic fungus that the ants use for food.

Back to our central question, can chocolate kill ants? Obviously caffeine can be a repellent and potentially have adverse effects on on insects. Caffeine is only a minor ingredient in chocolate, however. Chocolate is a conglomeration of some 300 different chemicals, any one of which could have an adverse effect on ants. Obviously more research needs to be done.

I was intrigued by this problem enough to set up a small experiment. I let you know more about that in an upcoming post.

What do you think? Do you know if chocolate has an effect on ants?

References:

Kim YS, Uefuji H, Ogita S, Sano, H. (2006). Transgenic tobacco plants producing caffeine: a potential new strategy for insect pest control. Transgenic Res. 15(6):  667-72. (Abstract at PubMed) (Google the title for a free .pdf version)

Carlos H Miyashira, Daniel G Tanigushi, Adriana M Gugliotta, Déborah YAC Santos. (2012). Influence of caffeine on the survival of leaf-cutting ants Atta sexdens rubropilosa and in vitro growth of their mutualistic fungus. Pest Management Science. 68 (6): 935–940.

Nathanson, James A. (1984). Caffeine and related methylxanthines: possible naturally occurring pesticides. Science 226: 184-187.

For more about chocolate and how it is made:

Ask-a-Scientist at Binghamton has general information about how chocolate is made

For more depth try The Science of Chocolate by S.T. Beckett (link goes to an excerpt at Google Books)

Recently a reader had a question about ant anatomy. "I want to know the division of the ant's body where the head, chest and abdomen and what is from the antennae and legs and wings, eyes, etc."

In general, insects have three body parts: the head, thorax, and abdomen.

In ants, however, the main body parts are not as easy to tell apart.

When adult ants are developing their lovely thin “waists” within the pupa, a bit of the true abdomen gets pressed up against the thorax, and the rest of the abdomen becomes the "waist" and the hind section. When ant biologists realized this problem, they thought,  “Hum, we can’t really call that middle section a thorax, if it’s really a thorax and a bit of abdomen pushed together. And we can’t call the back section an abdomen if it’s only part of the abdomen… so we’ll call the middle part a mesosoma (in older literature an alitrunk) and the back part a gaster (or metasoma)." The thin part between the mesosoma and gaster is called the petiole. The head is still a head.

In some ant species, the "waist" is longer and consists of two segments, which are called the petiole and postpetiole.

Roberto Keller has an excellent illustration of the segments that make up the true abdomen.

Scanning Electron Micrograph, Roberto Keller/AMNH)

The bit of abdomen that joins with the thorax is labelled as I in this diagram. It is called the propodeum. The segments labelled II and III are the petiole and postpetiole. The rest form the gaster.

If the ant is a queen rather than a worker, you will see either the wings attached to the mesosoma (labelled as trunk), or wing scars where the wings were attached.

Hopefully that helps answer your question.

If you have anything to add, please leave a comment.