Hello everyone! Today, let’s embark on a fascinating journey into the world of Polyrhachis dives, also known as the golden-tailed ants.

Polyrhachis dives exhibit a remarkable adaptability, thriving in a wide range of environments, including bamboo groves, humid regions, mangroves, and canopies. They are also commonly found in semi-urban areas such as parks and gardens, and can be observed at elevations up to 2100 meters above sea level.

These medium-sized, golden ants are arboreal, residing predominantly in the trees of Southeast Asia, from Japan to northern Australia. In Australia, they prefer open savanna-woodlands and swampy coastal plains. Here, they construct large, multi-chambered nests from silk and carton, integrating these structures within the branches and leaves of small trees and shrubs.

In Okinawa, Japan, these industrious ants glue leaves together with larval silk to create their arboreal nests. Recently, they’ve been expanding their range northward on the island, though the reason for this population increase remains a mystery.

Now let’s dive into what makes them so special. Dives workers are usually between 6 and 8 mm long, while the queens are much larger, around 12 mm. They have an amazing metallic sheen with shiny yellow or silver bands on their large gaster, making them stand out from other Polyrhachis species. This is why they’re often called golden-tailed ants.

The etymology of their name provides insight into their appearance: “Poly” translates to “many” in ancient Greek, and “rhachis” denotes “ridge” or “spine.” Their mesosoma, or midsection, is characterized by the presence of spines at its termini, which serve as a defensive mechanism against predators such as reptiles. These ants are easily identifiable by their dense, silver hairs that cover their entire body, with a particular concentration on their gasters.

Polyrhachis dives are monomorphic, signifying that individuals generally exhibit a uniform appearance, although slight size variations can be observed between generations. Furthermore, there are regional differences: Asian P. dives possess deeper notches on their heads and more curved spines compared to their Australian and New Guinean counterparts.

Notably, these ants demonstrate gyno-polymorphism, indicating the presence of two types of queens: microgynes, which have a slightly larger mesosoma than the workers, and macrogynes, which are significantly larger. Both queen types can coexist within the same colony.

Polyrhachis dives colonies can accommodate multiple queens—up to approximately 50 queens collaborating harmoniously. This arrangement facilitates the growth of their colonies to considerable sizes, sometimes comprising tens of thousands of worker ants. Their super-colonies can be so densely populated with workers and queens that accurately estimating their population becomes challenging. Each nest can house from a few hundred to several tens of thousands of ants, including numerous queens.

Polyrhachis dives are well-known for their aggressive behavior when threatened. Despite lacking stingers, they possess a classic defense mechanism: they can spray formic acid from an acidopore located at the posterior end of their abdomen. This trait is characteristic of Polyrhachis ants, although the intensity and frequency of this behavior can vary.

In addition to their aggressive tendencies, these ants consume food in substantial quantities, exerting a significant impact on their ecosystem. They actively hunt and scavenge for insects and gather sugar-based food. They are capable of consuming a cricket down to its exoskeleton.

In an experiment with an indoor colony, it was observed that organic honey was exceptionally well-received by the ants, highlighting their fondness for this particular food source.

Polyrhachis dives build their nests in a globular structure using a variety of materials, including soil, small stones, plant matter, and even animal feces. This mixture creates a mortar to bind leaves and other plant materials together, forming intricate and durable nests.

They use silk to shape their nests, created by their larvae just before they reach pupation. This work requires less cooperation than Oecophyllas’ weaving style, but they still collect materials from the ground.

Sadly, they’ve had to adapt to humans, building their nests from our trash and abandoned structures.

Studies show that early Polyrhachis ants lived in trees and used larval silk to build nests. Over time, some species moved underground and stopped using silk. However, a few species returned to living in trees without using silk, while two species use spider silk to build nests on rocks. Silk in Polyrhachis dives is unlikely to provide protection against parasites, nor does the carton they build.

Couple of final tidbits: Polyrhachis dives queens have a relatively short lifespan of about 12 years, which is quite long for an insect but not much compared to Lasius queens that can live up to 30 years.

Polyrhachis dives ants help regulate pests on trees and are part of the diet of the endangered Chinese pangolin, making them ecologically important.