Ant behavior: December 2010 Archives

Can ant colonies reproduce and sustain with no queen? And what is the role of the queen in the actions of the other ants? Has it been found to have any instruction, or only egg laying? (Angela, Baton Rouge, Lousiana, USA)


Hi Angela,

In a "typical" ant colony, there is one or several queens that have been fertilized on their mating flight before colony founding. These queens lay eggs. The queen can lay fertilized eggs, which will develop into females (workers or - when the colony is mature - workers and new founding queens). The queen can also lay unfertilized eggs, which then develop into males. If there is only one queen per colony and this queen dies, the workers can start to lay eggs. But since the workers have not been fertilized, these eggs only develop into males. Males don't contribute to maintaining the colony, they will fly off once mature to mate. So the "typical" colony cannot sustain without the queen. However, there are some ant species (e.g., Platythyrea punctata), in which workers are clonal and lay eggs that develop into females. In these colonies, the most dominant worker will lay eggs while the others maintain the colony. Once this reproductive worker gets weaker or dies, another worker will become the reproductive. A really nice review on exceptional colony structures is "The demise of the standard ant" by Jürgen Heinze.

Coming to your second question: Ants communicate with chemical signals. These can be pheromones or cuticular hydrocarbons. The queen produces a range of pheromones and by this gives instructions to her workers. One important instruction is that the workers don't lay eggs. It is in the queen's interests that she is the only egg-layer and the workers nurse her offspring, forage and defend the colony. So the queen produces pheromones that suppress the ovary development of the workers. Once the queen dies, the workers will start to develop ovaries to lay unfertilized eggs and these will develop into males. Please also read this post on ant pheromones.

All the best,
Steffi Kautz & the AntAsk Team

Specifically, I am asking if there is any record of it occurring. I imagine that the odds of it happening are extremely low, if not zero!

Thank you,
Josh


Hi Josh,

Thank you very much for contacting AntAsk! Actually, this is a really good question. At first glance ant colonies seem to be organized in a standard manner, with one queen per colony. The queen has mated once and she produces workers that are all full sisters. However, when we start taking a closer look at the organization of ant colonies, there seem to be more ant species that have some kind of exceptions than the ones that don't. A really great review on this topic is the paper "The demise of the standard ant" by Jürgen Heinze.

There are some ant species, which don't really have a distinct queen, but special workers that lay eggs and are called "reproductives". One example is Platythyrea punctata. This ant is clonal and theoretically all the workers have the potential to become the reproductive of a colony. In these cases, a single worker could leave the colony and have her own colony. But workers don't leave the colony purposely. It is really risky to found a new colony all on their own and they have a much higher chance of success when they work as a colony. However, if the old reproductive dies, the colonies of these clonal ants can live on. When a workers gets separated by her colony and she is in good health, I suspect, she would try to start her own new colony.

Another case in which ant workers would leave their colony is when they have an infection. Some ants in the tropics might catch an infection by the entomopathogenic fungus Orthocordyceps. A great YouTube video of an infected bullet ant (Paraponera clavata) is found here. At a later stage of the infection, the fungus grows into the brain and alters the infected ant's behavior. The ant leaves the colony, climbs up to the top of a plant and secures itself with its mandibles and dies. Then, fungal fruiting bodies sprout from the dead ants head and explode releasing the spores to infect other ants and complete the fungal life-cycle.

All the best,
Steffi Kautz & the AntAsk Team

Dear AntAsk,

I'm designing a behavioral experiment about nest-mate recognition in ants that I hope to publish in an educational journal. When I do the experiment with my class here in Oklahoma, I've been using harvester ants of the species Pogonomyrmex barbatus, but I understand this ant doesn't occur everywhere, and I'd like to offer educators from other areas suggestions for what kinds of ants might work.

Thanks!
Stephanie


Dear Stephanie,

That sounds like a really fun, educational activity! Pogonomyrmex in general are great to use, but here are some other genera that might be useful to people living outside of your region:

Formica spp. (wood ants) These ants are widespread in North America and Eurasia, and are often the most numerous large ants in boreal forests. They build mounds of vegetation (sometimes to 1m high or more) around their nest entrances.

Tetramorium caespitum (pavement ants). The most commonly seen ants on sidewalks in urban North America and Northern Europe. They often have nests with multiple entrances, so get ready to see some non-aggressive behavior, too. Ants truly from a different colony, however, will be violently rejected, and closely-spaced colonies of this species are frequently seen having all-out territorial wars (see previous post here ).

Aphaenogaster sp. and Messor sp. Also referred to has harvester ants, these ants have very similar habits and life-histories to Pogonomyrmex; all three genera co-occur, and are most common from southern California to west Texas.

The majority of ant species show some degree of internidal (between-nest) aggression, so most ants are worth a shot, with the following exceptions: most invasive ants. The Red Imported Fire Ant, Solenopsis invicta, is common and obvious from Texas to Florida. These will often not show aggression to other members of its species. The Argentine Ant, Linepithema humile, is very common in South and Central California; these ants rarely show aggression towards each other in their introduced range (there is actually a "mega-colony" that occurs in Japan, California, and the Mediterranean region in Europe; you can read more here ). Both ant species are originally from temperate South America, where they actually do often show internidal aggression. Many invasive ant species form polydomous and polygynous (multi-nest and multi-queen) colonies and show little internidal aggression in their introduced range, but have more "normal" nest structure, queen number, and levels of internidal aggression in their home ranges.

I did not really address how to identify these ant genera in this blog post, other than to direct you to some pictures. For an entry-level guide to identifying many of the relevant genera discussed above, please see this key, developed for the Bay Area Ant Survey.

For more in-depth information on ant identification, I would highly recommend checking out "The Ants of North America" by Brian Fisher and Stefan Cover.

Hope this helps!
Best,
Jesse Czekanski-Moir & the AntAsk Team

Hi guys!
My name's Mark from the Philippines. I hope you don't mind several questions that aren't necessarily related. :)

1.) I noticed most ants are either black or red. Sure there are whitish ants and some colorful Polyrachis ants but they're minorities. By black I mean dark brown to shiny black and by red I mean the many variations(reddish orange, orangeish, brown reddish etc). What's so special about the two colors? I'm guessing ants' ancestors happen to be black and red wasps and since ants don't need color change to adapt they retained their colors but what do I know. :)

2.) What's up with the way leafcutters look? Atta, Proatta, Acromyrmex etc have this thorny bodies that doesn't make sense to me. What's so special about leafcutting and fungus-growing that they need to evolve with spiked bodies? And also Polyrachis. They have this few large spikes that doesn't seem to have any significance other than birds or lizards might get pricked if they try to eat them and aesthetic purposes.

3.) I found these colony of what seems to be Crematogasters basing on their "heart-butts". They've occupied an abandoned termite nest and when I breached the walls, out came big-headed blockers. So far I haven't heard of trimorphic Crematogasters but the ones I found are, so any idea what species this might be? And also I find it weird how they have these termite style defense when others ants seem to find them distasteful. I dropped one at Pheidoles, Tetramoriums, Solenopsis, Tapinoma and Pharoah ants and they were left untouched. Even dead ones weren't scavenged. Pheidologetons might be their enemies? If so, can you tell stories about them raiding Crematogasters?

4.) I noticed these odd behavior in Pharaoh ants. A medium sized worker seems to be biting a larger worker on the neck. There wasn't any obvious signs of distress on both ants. I first guessed it was grooming but they looked totally stiff which doesn't look like grooming to me. When I disturbed them with my fingers, they appeared confused but that's obviously by the huge thing that touched them. Then they just went of with their marching nestmates. I saw 2 of these weird happening from the same colony, simultaneosly and a few inches apart. Both pairs where a median "biting" a major. Any idea what that was?

5.) I witnessed these funny grasshopper kicking garden ants. At first it was facing incoming ants and then turned around to kick them a few inches away. The ants landed exactly on another of the ants' lines which made even funnier. Is these a unique grasshopper or do many grasshoppers do these?

Thats all! Thanks!
Mark


Dear Mark,

Wow, that's a lot of questions! We'll try our best to answer them, but for most of these, we'll just be giving our best guesses, because without more information, we don't know.

1) So your first question sounds like you're asking "Why aren't ants more colorful?" But then you go on to list all the different colors that ants can be! The different shades of red, yellow, brown, and black that most ants come in are special because these are called pigment colors. They are the most common chemical-based colors in all groups of animals. Human hair, for example, is basically all the colors an ant can be. The colors ants and mammals usually aren't are the structural colors that are so flashy and beautiful in many birds, beetles, butterflies, and dragonflies (check out this website about birds for more information about the different kinds of colors animals use). The few ants that are colors that mammals usually aren't use structural colors (there are green ants and blue-ish purple-ish ants). Part of the reason ants aren't as colorful as butterflies or dragonflies is that they don't rely on visual cues for mate recognition or for sister-recognition. Instead they rely almost entirely on touch and smell. Ants aren't usually as colorful as orchid bees or velvet ants because they don't rely on aposematic, or warning coloration, to warn predators that they are dangerous. In fact, the ant body type and their habit of working together in large groups is distinctive enough that many arthropods have adapted to look like ants - they don't need to be bright orange and white to be intimidating because ants are notorious enough as it is. (see previous posts here and here on myrmecomorphy ). As you observed, ants still come in an impressive array of hues; all the pigment colors found in most other organisms are found in ants. Blues, greens, and bright whites are usually absent in ants because they don't need them for recognition, communication, or for warnings.

2) Again, you've pretty much answered your own question here. Lizards and amphibians are some of ants' most significant predators, and anything ants can do to make themselves less easy to eat would be an advantage. Something you might notice is that none of the ants that are very prickly have serious stings. There are trade-offs involved in how much energy you devote to different kinds of defenses: spines take a lot of extra nutrients to produce, just like venom. Some ants avoid predation by being fast, like members of the genera Anoplolepis and Paratrechina. Leaf-cutter ants in the genera Atta and Acromyrmex are some of the most conspicuous ants in the Neotropics. They can't run away from lizards while they're carrying those huge chunks of leaves, so they've devoted a lot of energy to being prickly and crunchy.

3) We don't know of any dimorphic Crematogaster. A genus that is often found in termitaria that is conspicuously dimorphic is Metapone. This genus is known from the Philippines, but little is known about its natural history. The observations you've made may be new to science! It's important to keep voucher collections of the ants you find and conduct behavioral experiments on, so they can be positively identified. There are more than 80 genera known from the Philippines, but this number is expected to grow with more collections. If you have pictures of these ants, send them our way, and we can try to identify them! Or at least check out the Ants of the Philippines on AntWeb, and Ants of Borneo.

Your experiments on whether or not the other ants wanted to eat your "Crematogaster" might be more meaningful if you conducted them using a delicious positive control. Perhaps the other ants had no appetite because they were afraid of you! If you offered the ants multiple kinds of food at the same time (sometimes called a cafeteria experiment ), then you'd know that at least they were in the mood to eat something.

4) How closely did you look at the Pharaoh ants? It could be that the "majors" were actually wingless reproductive females. In larger Pharaoh ant colonies, there are often multiple queens, and sometimes they assist in foraging (which is part of why they are so easily spread by humans--if a queen happens to be foraging in your lunch box when you pick it up and take it home, you've just started a new Pharaoh ant colony!). The true workers will still take it upon themselves to carry the queens around sometimes, though. We don't understand exactly why they do this, but it could be a relict from when they used to be monogynous.

5) That's really funny. Very little is known about insect behavior in the tropics. Most larger insects will try to flick ants away from themselves if they are being harassed. But wouldn't that be cool if they could flick them into another angry line of ants? If you could demonstrate this by doing statistics on how likely an ant was to be flicked by a grasshopper into another ant line vs. just anywhere, that would be a great scientific paper!

Sorry we can't give you more definite answers to many of these questions, Mark. But if people like you keep making great observations like these in different areas in the tropics, maybe someday we'll know for sure!

Best,
Jesse Czekanski-Moir, Noel Tawatao, & the AntAsk Team