[march 2023: this page is in progress… you’re welcome to check it out now, but hopefully there will be more here by the end of 2023]
For some great photos and taxonomic information on Palau ants, please visit the Palau page on AntWeb:
https://www.antweb.org/taxonomicPage.do?rank=genus&countryName=Palau
Introduction to ant diversity in Palau:
Ants are a type of insect that is related to bees and wasps. They usually live as a family unit: the colony. Most ants are “eusocial,” which means they live together with their extended family, and many ants cannot reproduce. The ants you usually see are called “workers,” and they are sterile females. Queen ants lay all the eggs for the colony, and because of this the last part of their body is often much larger than a typical ant. This might be part of the reason why one of the words in the dictionary for “ant” is “Kedolsabtil.”
Worker ants gather food, protect the nest, and help take care of the younger ants. Ants have a life cycle like a butterfly: they start out as an egg, then hatch into a larva, then they go through a pupa phase and then turn into an adult (scientists call kind of insect life cycle “complete metamorphosis”). The larval ants don’t look like they can do much, but in most ant species they help chew large pieces of food the adult workers bring back to the nest. Ants share food with each other by vomiting into each other’s mouths—the same way a mother bird feeds her babies, baby ants share the food they chewed up with their adult sisters and mother!
And what do male ants do? Well, not much, usually. While they are growing up, their sisters need to protect them and take care of them. But when they’re ready, they can fly away and try to find a mate. Many male ants don’t survive for long after mating, so their lives are mostly just being helped by their sisters for a few months, and then a day or two of flying and mating, before being eaten by a bird, a bat, a spider, or a dragonfly.
How are ants part of Palau?
Ants often become food for lizards, birds, bats, spiders, dragonflies (and other large, predatory insects). They are also a major part of the “food” for pitcher plants. But before they become food, different ant species have a variety of roles in the forests and savannahs of Belau. Many species of ants are predators: they eat and scavenge many small animals. Some ants have special relationships with insects that drink phloem from plants. For example, scale insects drink plant sap, almost like a mosquito taking a blood meal. But because the plant phloem is so watery and nutrient-poor, scale insects are constantly eliminating sugar water as they drink. The ants drink this, and offer protection in return, almost the way humans herd sheep, cows, or goats. There are many ant species that can do this sometimes (documented in Idechiil et al. 2007), and a few ants that must do this to live. Many ants are also very important for moving plant seeds around, and improving the soil.
What do ants do?
Some ants have partnerships with other organisms. There are ants that have partnerships with other insects, like these ants tending scale insects. There are also ants that are important seed-dispersers. Leaf-cutter ants in tropical areas in the Americas use the leaves they cut to farm fungi. In some places, ants improve the soil at least as much as earthworms. Ants are often very important scavengers, and predators of small insects.
Ant distributions
Ants live almost everywhere there is land that is not frozen most of the time. There are more than 14,000 species of ants in the world, and about 100 of them have been recorded in Palau. Of this total species list, about ⅓ are introduced or invasive, ⅓ are widespread, native species, and about ⅓ are endemic. Many of the ants you can find in your house or kitchen are introduced or invasive ants which occur in many tropical countries.
Invasive ants in Belau:
Even though ants have many important roles in Palau’s forests and savannahs, when most people think of ants, they think of them as pests in their kitchen, or on the beach. Usually, if you see an ant in your kitchen, it is a widespread introduced or invasive ant. Many of the ants that live around people have Palauan names, like the ones below:
Tekoi er a Belau: Chetor (or chetol)
Scientific name: Anoplolepis gracilipes
English name: Yellow Crazy Ant / Longlegged Ant
Chetor do not have stingers like most other ants (especially Bembangch and Omaikesuch). Instead, they can squirt formic acid out of a hole near the back of their bodies. This acid will not hurt if it touches your skin, but if you have a small cut near where they squirt you it will feel like getting lemon juice in your wound. If you pick one up, you might smell something like vinegar. From the ant’s perspective, this isn’t a good defense against humans or most other large animals, but it is a very effective offensive and defensive weapon against small insects, spiders, worms, and snails. On Christmas Island, near Indonesia and Australia, these ants are so abundant that they have killed many of the land crabs by attacking their eyes with their acid. So far, in Palau, they do not seem to be major ecosystem disruptors, but they often become more abundant in the forest if there has been some kind of construction (like building a new trail). Some Palauan people like them in their kitchen, because they don’t sting, and they chase other types of ants away! They are considered introduced and invasive throughout the Pacific Islands. Scientists aren’t sure where they are originally from: possibilities include East Africa, South Asia, and/or Southeast Asia.
Tekoi er a Belau: Bembangch / Akari
Scientific name: Solenopsis geminata
English name: Tropical Fire Ant
Bembangch are fairly common in sandy soils around people’s houses, or other places people like to gather and eat food (like some of summer houses in the Rock Islands), but they usually aren’t in people’s kitchens, or deep in the forests. They are originally from tropical parts of North and South America, and may have been brought to Palau during the Spanish colonial times (although it’s possible they arrived sometime after that from the Philippines or Indonesia). They have a painful sting, and in some small sandy islands, they can be very harmful to nesting birds and sea turtles. In most of Palau, people call them “Bembangch,” but in Angaur sometimes people say “Akari,” from the Japanese words for “red ant” ( 赤アリ ; pronounced “aka ari”).
Tekoi er a Belau: Metmut
Scientific name: Tapinoma melanocephalum
English name: Ghost ant
Metmut often refers to a very small, fast ant that lives in people’s kitchens, both in Palau and around the world, especially in the tropics. Their English name, “ghost ant,” might be because they are so small and quick, and parts of their bodies are translucent, so it can be difficult for some people to tell whether they’re really seeing ants or not. They are especially fond of sugar, so people usually notice them near where they store sweets, or after they’ve spilled something sugary. They’re good at chewing through thin plastic bags, and although they don’t sting, some people can feel them biting. You can also see them and some of their close relatives around flowers in the forest and savannas of Palau. Metmut are found all around the world, especially in the tropics, so if you travel to other tropical countries you will often see their familiar speedy activity. Metmut are in the same subfamily (Dolichoderinae) as Chedib el Buuch, so if you pick them up and smell them, you might smell something like citronella.
Tekoi er a Belau: Chedib el Buuch
Scientific name: Technomyrmex spp.
English name: (T. albipes is sometimes called the “white-footed ant”)
The Palauan name literally means, “ant of the betelnut palm,” so someone could call any ant they find on a betelnut palm, “Chedib el Buuch.” But usually, if you notice a trail of small, black ants going up and down the trunk of a tree in Palau, they belong to the genus Technomyrmex. There are likely two or more species in Palau that all look very similar—“Technomyrmex spp” means that there are multiple members of this genus here, including at least one that might be considered native or endemic (it has a close relative in Papua New Guinea), and one that is invasive (Technomyrmex difficilis). In many forests in Palau, this might be the most abundant ant, so it is important that we learn more about its history in Palau.
Native/indigenous ants in Belau:
Tekoi er a Belau: Omaikesuch
Scientific name: Odontomachus simillimus
English name: “Trap-jaw ant”
If you see a large, somewhat slow-moving ant in the forest in Palau, look out! They have a painful sting! These ants are native to Palau, and occur from American Samoa and Fiji to islands in the Indian Ocean. They are actually closely related to some ant species in South America that somehow made it out to the Pacific islands about five million years ago. These ants are called “trap-jaw ants” in English because their jaws (mandibles) can be opened 180 degrees, and then closed very rapidly to kill or stun prey. There is another species of trap-jaw ant called Odontomachus malignus that lives in intertidal areas, especially in the rock islands. This ant is slightly larger than O. simillimus, and is a bit more brownish-red in color (although you might need to see them next to each other to notice much of a difference). There are also different kinds of tiny trap-jaw ants in Palau, that are part of the distantly related genus Strumigenys. These ants are tiny, so you probably won’t see them unless you’re looking very carefully at lots of dead leaves and tiny sticks in the forest, but they have a fascinating diversity of trap-jaw shapes and sizes.
Figure 1 above: Palau native trap-jaw ants Strumigenys stemonixys, Strumigenys szalayi, Strumigenys godeffroi, Strumigenys emmae, Strumigenys mayri, and an undescribed, endemic species of Strumigenys.
The rarest ants in Palau?
If you’ve spent time in Palau, you likely have the impression that ants are very common here. But not all species of ants are!
When a species has status as “endangered” or “critically endangered,” that’s a very important piece of information, but the process of formally listing species with the IUCN requires data that, ironically, for some of the rarest species, might be difficult to figure out. There are several endemic ants in Palau that are only known from one collection event. Because usually it’s best to formally describe species based on multiple individuals, some of these rarest of Palau ants have also never been given a scientific name. In some cases, it is possible that there is something about the ecology of these ants that simply makes them difficult to collect, but it is also possible that these ants are all extremely rare, and some of them may already be extinct.
Leptanilla palauensis
This ant was collected in the 1950s, and is only known from one male specimen which, unfortunately, is missing its head. Note the wings, and the body, which looks similar to some small wasps. Based on what is known about this ant’s relatives in Asia, it is likely that colonies usually stay underground, which might make them difficult to collect.
Rhopalomastix sp.
This is an undescribed species that was only collected once on Mecherchar, near Eil Malk. Ants in this genus usually live under tree bark, so it is difficult to search for them without injuring many trees, so it is possible this ant is more widespread in Palau.
Myopias sp.
An undescribed species known only from one individual collected on Peleliu island.
Some members of this genus nest in rotting wood on the forest floor, and others might mostly be subterranean, so it is difficult to guess where to look for more individuals of this species. It may genuinely be extremely rare, and possibly restricted to Peleliu island.
Rostromyrmex sp.
A single worker from this undescribed species was found in Ngeremlengui. Only one other species from this genus is known from Malaysia, so it is exceptionally rare both as a species, and as a genus.
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