The dustfly (Polliniculex) emerged in the Middle Muricene as an offshoot of the larger sugarfly family. Abandoning its relatives' nectar-stealing habits, it developed a mutualistic relationship with a particular group of woodlouse-grasses, the swamp-dwelling sweetstalk (Culicosaccharus). By brushing against the grass's florets, it could spread pollen from one plant to another, reducing the amount of energy the plant needed to invest in pollen production. In exchange, the fly was granted safe passage to drink a bit of sugary sap from the surface of the sweetstalk. This partnership grew over the following 1.5 million years, blossoming into the unique arrangement seen in modern Apterra.

Sweetstalks are no longer restricted to the nitrogen-poor bogs they originated from - in fact, carnivorous plants like the pitcher-basket have largely outcompeted them in that environment. Instead, Culicosaccharus has spread across the globe, modifying its structure to suit nearly every environment. Members of the genus (and, by proxy, species of Palustrarthus and Polliniculex) can now be found in woodlouse-grasslands, temperate pseudoforests, tundras, deserts, and the few remaining patches of tropical jungle. A radiation of derived forms has iterated on its ancestors' adaptations, refining the three-way symbiosis between fly, crustacean, and grass.

The sweetstalk itself has undergone several changes over the years. In addition to whatever features are necessary to survive in each specific habitat, their process of nectar production has shifted. Now, instead of sap being secreted all across the leaves and stem, it is only deposited within and around the flowers themselves. This causes dustflies to spend more time brushing against the plant's anthers, picking up pollen grains that it then ferries across to the next sweetstalk. Unfortunately, this results in a shortage of food for the arboreal isopods, which can now no longer rely on that same nectar to fulfill their own dietary needs. Instead, they get most of their calories from defeated Plague woodlice, also feeding on the parasitic fungi they harvest, cleaning their host in the process. While this results in a smaller population of Palustrarthrus, it means that the sweetstalk can successfully support both of its allies without forcing them to compete with one another. 

The dustfly, too, is quite different from its earlier cousins. The halteres are now entirely flat and wing-like, though limited in size by their lack of complex venation. Dustflies' broad, soaring wings mke them slow fliers and reduce their agility. In exchange, they can travel long distances while expending little energy. At the moment, dustflies are the largest flying animals on the planet, with some measuring more than 15 centimeters from one wingtip to another. Most, however, are not much larger than an average mosquito. Like their Aedes ancestors, they have a stiff proboscis that cannot be curled up, forcing them to tuck their mouthparts underneath their bodies when in flight. This is no major hindrance when feeding; many sweetstalks have evolved a stiff glume just below each inflorescence that allows the dustfly to perch in an optimal position for both feeding and pollinating. As time goes on, the coevolution between these three genera is bound to lead all of them to increasingly strange places. With such explosive success across numerous biomes, this relationship stands a great chance of surviving far into the future.