Enter the Epoch of Bugs

It has been three million years since the ice melted. A new epoch has arrived, characterized by warm climates, high rainfall, and a carbon-rich atmosphere. Plant life has long since reclaimed lands once buried under glaciers, blossoming into a world of unparalleled diversity. Some of the survivors of the Ice Age have grown more specialized in their niches, while others have carved new paths unseen in the past. Apterra is a temperate world once again, with sub-freezing temperatures uncommon. Most importantly, oxygen levels have risen dramatically as a result of the increased rate of photosynthesis. This environment has produced some of the oddest animals ever to evolve, as clades formerly relegated to microfaunal roles begin to attain greater sizes. Filling ecological voids left by now-extinct Muricene vertebrates, Apterra's various insects, isopods, and other crustaceans have risen to dominance and, in more than a few cases, grown startlingly large.

Not all newly-dominant insects are giants. Relying on speed, numbers, and specialized mouthparts, the Locust Reaper (Locusticulex) is a common sight on the open grassland and savanna. Though their lineage nearly died out when the loop-grasslands collapsed, they managed to survive by shifting to a diet of closely related prairie-baskets and prairie-barrels. This helps avoid competition with Plague isopods, which have reverted to specializing on the once again abundant woodlouse-grasses. Locust reapers can easily decimate a swath of basket-dominated prairie in a matter of hours, eating twice their body weight in food every day. With tough, serrated maxillae, they find no trouble tearing through blades of grass, leaving only the roots alive. The piercing proboscis has shortened significantly, and it can open along its bottom edge to ingest small pieces of solid food. After consuming all available grass, the reapers then move on to another area, usually flying a few kilometers between each meal. Swarms disperse at the end of winter, with each female seeking out patches of untouched land to lay their eggs. After emerging from pools of water, newborn locust reapers search for conspecifics, releasing pheromones that others can follow to their source. Before long, a new swarm forms. Once again, millions of flies move as one. By eating the basket-grasses, they remove dry foliage that might otherwise spark wildfires, clear the way for other plants to grow, and fertilize the grassland with their droppings and corpses.

In the great hybrid forests, other herbivorous mosquitoes make their living by parasitizing palm-grass trees. Palmpeckers (Tenebrostris) are a group of sapsiphons with a taste for sugar-rich phloem. With wingspans of up to 30 centimeters, they cast an ominous shadow over colonies of arboreal isopods, which find great difficulty fending them off. Thankfully, the trees have other tricks to avoid having their sap stolen; many species route their phloem through the core of their stems, too deep for most parasites to access. In response, palmpeckers have evolved a massive proboscis, often as long as their whole body. In flight, this is tucked beneath the head to avoid snagging on branches and vines. When feeding, the mouthparts bore a hole into the target plant. If possible, the insect perches during this process, but when necessary it can hover and drill at the same time. After drinking its fill, it flees to a safe location to digest its meal.

On the forest floor, another titanic invertebrate plods along, its long body bending over fallen logs, stones, and other obstacles. This giant woodlouse is Tarsopulma, a descendant of basal non-bridgeworm dodecipedes. It squeezes into the burrow of a smaller animal, its skirted edges folding along the sides of its body. This opportunist would be happy to make a meal of the den's inhabitant if it were home. Finding it abandoned, the crustacean instead begins processing a small pile of hard-shelled seeds, then turns around to continue on its journey. While not particularly fast, the Tarsopulma's great endurance allows it to traverse over a kilometer every day. It occasionally comes across others of its species; if the two are of opposite sexes, they will almost invariably mate. Otherwise, the dodecipedes will simply pass each other by without conflict, as this genus retains some degree of pro-social instincts from its ancestors' days as small, skittish creatures that had no choice but to huddle together for safety. In the Arthrocene, such fears are unnecessary, as these 40-centimeter pill bugs have few natural predators. 

Entering a sunny meadow, a flock of large, slow-flying insects drink nectar and carry pollen between sweetstalks. These massive dustflies are Halteropteryx, measuring a quarter of a meter from one wingtip to the other. Their broad, translucent forewings are mesmerizing, blurring their outlines and confusing predators. Their massive halteres, on the other hand, are opaque. These repurposed sensory organs have a matte, gray-white coloration with a black dot in the middle, resembling the eyes of a large bird. Their bodies are flattened and lightweight enough to permit soaring over long distances; once they take off, Halteropteryx can ride thermal air currents, gliding above the treetops until they locate a new clearing. Scattered openings in the forest are the preferred habitat of many sun-loving flowers, providing ample food for the large mosquitoes. Smaller dustfly genera can be found throughout forests and grasslands, being less restrictive in their choice of sweetstalks.

The sea is home to even stranger forms of life. With an abundance of large algae in the water column, filter-feeders throughout Apterra's history have been incentivized to grow larger than their earthly relatives. As far back as the Middle Muricene, certain members of groups like the water fleas, copepods, and rotifers had doubled in size. This trend has been taken to extremes by the Floatifer (Fluitabella). This two-centimeter macroplankton drifts on the ocean currents, feeding on Volvox-like algae too big to fit in the mouths of smaller rotifers. With no spines, venom, nor even the ability to quickly swim away from threats, its only natural defense mechanism is its impressive rate of reproduction. Though it takes almost a month for floatifers to reach full size, they are born pregnant and can lay their first clutch of a dozen eggs in about four days. Any young born in this way are females and clones of their mother. On the other hand, older females do sometimes produce male eggs, stirring up the gene pool whenever deleterious mutations begin to accumulate.

Scouring the substrate of shallow coastal areas is the elusive Copabinia. This genus of crustaceans can reach 15 centimeters in length and is descended from algal-mat-eating copepods that once kept the red tide in check. With toxic floating mats now rare, Copabinia has switched to eating other dinoflagellates, especially those that grow on rocky seabeds near the shore. It has also expanded its diet to include many small marine animals, especially the helpless larvae of marine fish and arthropods. A good deal faster than floatifers, it evades its own predators by darting in and out of crevices. Its five pairs of hypertrophied swimming legs, which run most of the length of its body, can keep it going at full speed even while maneuvering through complex terrain. If a Copabinia ever accidentally wanders into an open, sandy area, it usually buries itself to hide until the coast is clear.

Deeper in the abyssal zone, the bottom of the sea is patrolled by an armored Caenarthrid called Lunocephalus, a mudeater crab just shy of a meter in width. With the deep layers of dead algae long since depleted, Lunocephalus must now search far and wide for morsels of food. Its wide, crescent-shaped head acts as a hydrofoil, allowing it to swim leisurely just above the muck. When it comes time to breed, this wing-like shape helps the isopod ascend to the surface rapidly. A large female can easily give birth to tens of thousands of mancae, which live planktonically for several weeks, growing to about a centimeter before descending to the seafloor to mature into adults, reaching their maximum size in three to five years.

These are just a small assortment of the wonderful creatures that populate the Early Arthrocene. While still relatively early in the history of Apterra, global biodiversity during this age has reached an appreciable fraction of Earth's for the first time. The instability and rapid changes seen during the Muricene are beginning to wind down as the world finally settles into a rhythm, and the next few million years will be characterized by a long period of stability. Radical alterations in body plan will become rarer as the innovators of the previous epoch settle into their newfound niches. For the majority of organisms, the Early Arthrocene will be a static phase in the punctuated equilibrium of evolution. However, for a few species - mostly ones that lived in stagnant obscurity before the Ice Age - the time of accelerated change is far from over.