As the classic public service announcement goes, “If you see something, say something.” But adherence to this precept clearly generates a problem: if you don’t see something, you won’t say something! It is perhaps because of this mental framework that subterranean ants have received such little work in the scientific literature, compared to their aboveground sisters. Either that, or studying subterranean ants is really hard. Whatever the reason for this historical lack of premier underground ant content, a recent manuscript by Mark Wong and Benoit Guénard in Myrmecological News is exciting indeed.
Avid readers will remember our article “Feeling Blue? So is This Ant“, in which we featured a beautiful blue ant. Today, we add another ant to our color wheel:
This queen is not green with envy, but green with being Oecophylla smaragdina, a widespread species of weaver ant. Why is it green? Who knows!
We all know how ants forage for food. A bunch of workers are sent out randomly, then, upon finding some delicious munchie, each worker lays a chemical trail back to her nest in the hopes that other workers will follow suit. Whether or not nest mates do in fact reinforce a given trail is dictated largely by an emergent, semi-random selection process involving factors like the evaporation rate of trail pheromones, distance of a food source from the nest, and the size of the food source. So, that’s how all ants forage for food. Except it’s NOT!
Sometimes, The New York Times is depressingly anti-ant. Other times, it produces excellent ant-friendly content such as this video recently sent to The Daily Ant by Comic Correspondant Matthew Hernandez and Field Correspondant Ana Rita:
Ants are all kinds of smelly, and a recent study in PNAS advances our understanding of the molecular and genetic bases of these smells. See here for Vanderbilt University’s coverage of the study, and enjoy the below video produced in concert with the study’s publication. Thanks to Coffee Correspondant Ciara Reyes for bringing our attention to this study!
The reproductive system of most ants is pretty freaky, by human standards. Unlike in our species, where all individuals have a diploid set of chromosomes, nearly all ant species utilize a “haplodiploid” system in which females are diploid and males are haploid, with only one chromosome for each chromosomal site. So, in order to produce males, a queen lays unfertilized eggs, while in order to produce females, the eggs must be fertilized.
This is an extrafloral nectary:
Extrafloral nectaries, or “EFNs”, are little sources of sugar and nitrogen produced to entice ants to visit host plants. The plants, in return, enjoy the significant defensive capabilities of the ants, which often repel herbivorous insects. Given this benefit, it is perhaps not surprising that many different plant species and clades have evolved EFNs. But although these conspicuous structures have received much attention in the scientific literature, ants also benefit from a different, understudied “structure”: plant wounds.
Like EFNs, plant wounds (typically caused by herbivore munching) also excrete sugar and amino acids. Of course, this only further damages the plant – or, does it? The authors of a recent study in The American Naturalist investigated the “ant-wound network” in subtropical Jianxi, China, and also considered the implications of their findings for theories of EFN evolution.
The researchers (Dr. Michael Staab and colleagues) examined leaves from 10,000’s of trees over several years, documenting cases of ants feeding at herbivore-induced plant wounds and analyzing the nutrients present in wound sap via high-performance liquid chromatography. Their key finding was that 22 species fed on plant wound sap and did not exhibit specialization – plant wound feeding appears to be a facultative, opportunistic behavior in ants. Furthermore, the ant community feeding at plant wounds were a subset of the community that tend Hemipteran (“true bug“) mutualists.
Besides being a very nice documentation of an under-appreciated and apparently widespread ecological interaction, what do these results imply? In an enjoyable Discussion section, Staab and colleagues offer some suggestions. One particularly interesting hypothesis is that plant wounds are an evolutionary bridge to EFNs, an idea that is supported by the widespread and functionally similar nature of plant wounds uncovered in the study. The researchers also posit that ants feeding on plant wounds may not actually be mutualistic, and the food source may simply provide the ants some extra energy on their way to more nutritious food sources. If this is the case, the remarkable ecological dominance of ants in forest canopies may partially be supported by wounded plants – a little morbid, but very intriguing!
Termites are not ants. Yet, in also being eusocial, termites exhibit several behaviors that resemble ants, such as foraging for food via chemical trails. Termites and ants are also natural enemies, and several ant species are specialist predators of their distantly-related insect cousins. But how do the ants track their prey? A study recently published in the Proceedings of the Royal Society B reveals one sophisticated method: Exploiting the chemical trail laid by the termites.
Xiao-Lan Wen and colleagues conducted simple but effective field and lab experiments using the common predatory Ponerine ant Odontoponera transversa and three local termite species in southern Yunnan province in China. They found that the two primary trail pheromone components, DOE and DDE, were differentially abundant depending on the stage of foraging in the termites. In particular, DOE was more abundant at the onset of recruitment to a food source, while DDE became more abundant as more termites were recruited.
But what does this have to do with the ant predators? Well, Wen and colleagues also showed that O. transversa workers were more responsive to DDE, the pheromone component associated with a larger number of termites recruiting to a food source, strongly suggesting that the ants have evolved a chemical discrimination ability that increases the likelihood of the predators catching more prey. In other words, the ants have cracked the termite trail code!
This week was an odd one. It featured Theatre Thursday on Wednesday, Philosophy Phriday on Thursday, and an endorsement of ants by a key public defender of James Comey the same week the latter testified before Congress (oh, and that was weird too). So, we’ve decided to continute the oddity with a special edition post featuring a NON-ANT ARTHROPOD! In particular: spiders.
The Daily Ant typically maintains a #twolegstoomany policy in relation to spiders, but we nevertheless respect the creatures, and we can admit when arachnids amaze. Recently, Celestial Correspondant Andrew Burkhardt shared with us two spider stories that are out of this world.
The first is a story about how spider eyes are like Galilean telescopes, and thus are likely able to resolve the moon in the night sky. Check it out!
The second is live documentation by Correspondant Burkhardt of a spider that’s been in space. This spider is now housed in the Air and Space Museum, after a stint on the Skylab space station participating in an experiment on whether or not spiders can spin webs in zero gravity. Even though ants have also been to space, this space spider is pretty cool!
On Monday, a neat new study was published in Myrmecological News. This study, by Dr. Eduardo Gonçalves Paterson Fox and colleagues, tracked the development of trap-jaw ants and produced some sweet SEM images of the ant babies.
One of the authors, Dr. Adrian Smith, also produced a nice video where he explains this study to teenagers. Enjoy!
Polydomy. It’s a thing. It’s a thing where a single ant colony occupies completely separate nesting chambers rather than a single nest site. Polydomy, in creating a more distributed nest structure, has been theorized to increase foraging efficiency and enhance acquisition of a more diverse set of resources. Yet, despite the prevalence of hypotheses and theoretical work relating to polydomy, little work to date has experimentally tested the impact of polydomy on foraging efficiency.