Foliopteryx

Foliopteryx is a small genus of mosquitoes belonging to the locust reaper family, Locusticulicidae. Though it has the generalized mouthparts typical of its family, it spends most of its time focusing on a single food source. All Foliopteryx species have a rigid fold line running down the middle of the wing, leading to a shrouded, cryptic appearance when at rest. But this feature is not just an adaptation for camouflage; it allows these large, leaf-eating harpoonjaws to survive the onslaught of arboreal woodlice they face every hour of their adult lives. 

Though it can process a variety of foods with their rasping, serrated maxillae, Foliopteryx finds its greatest success when tackling a type of plant matter that no other flies can - the blades of palm-grass trees. Foliopters have little competition for this food source, as Plague woodlice don't find much success against this age's cast of hyper-specialized tree defenders. In fact, for the past two million years or so, Pestilarthrid isopods have become almost entirely restricted to open environments, and even there they face fierce opposition from plains-specialized locust reapers. In the forests, though, Foliopteryx reigns supreme. Its folding wings grant it the ability to tuck and dive with great precision. In the dense greenery of many Apterran trees, this is an absolute necessity; the slightest wrong move, and a darting insect could find itself stuck in a glob of sap, doomed to wait until the tree's inhabitants discover and dissect its helpless body. 

When feeding, a Foliopteryx can land for at most a minute at a time. As soon as it inflicts any damage on a leaf or stem, the palm-grass begins releasing volatile pheromones that attract its resident Scansoriarthriform pill bugs, who arrive in a frenzied state, indiscriminately attacking any unfamiliar animal. Foliopteryx, by this point, will have already vacated the tree, often taking just a single large bite from each plant it visits. This lifestyle is only possible because of how energy-rich the leaves of many palm-grasses have become in recent epochs; with increasingly adept defenders, the trees have taken to storing massive amounts of sugar in their foliage, improving their ability to survive long periods of drought or soil nutrient scarcity. In turn, this has made the trees an ever-more-tempting food source for herbivores of all kinds. For now, though, few other animals have evolved the traits necessary to take advantage of these abundant resources. Flightless arthropods, downlings, girraspbirds, and a handful of swattermice are the only others who regularly reach the canopy and compete with Foliopteryx, but none of them possess its combination of advantages: flight, low metabolic demands, and a body small enough to move freely through the leaves. These traits make foliopters Apterra's most generalistic arboreal folivores, leaving the rest to specialize in their shadow.

But Foliopteryx flies don't spend their entire lives buried in the canopy. In order to find each other and reproduce, scattered individuals must rise above the treetops and mate on the wing. In tropical regions, this occurs sporadically year-round, but temperate species display a spectacular synchronized nuptial flight every autumn. As food supplies dwindle, males change from their normal leaf-mimicking greens and browns to a palette of red, black, and yellow. They all take off together, triggered by a combination of starvation, shortening days, and changing weather. Ascending up to a kilometer into the sky, they don't have to worry abut saving their energy, for they won't need it after this day. They struggle for dominance high in the air, and the losers of these fights rain down onto the trees. Most of these corpses are eventually collected and processed by arboreal isopods, who recycle this ample protein source into their own bodies and thus, ultimately, fertilizer for their host plants. 

Meanwhile, the females, who until this point have been waiting patiently in the forest below, notice the first few dead males, which they take as a sign that it's time to join the orgy in the sky. By the time they reach open air, the males have become surprisingly placid; their instincts tell them to stop fighting once their numbers drop to a low enough density. Males who still have enough strength begin spiraling higher and higher, gathering harems as they go. Females aren't picky; they simply let exhaustion weed out the weaker males. Males who die from overexertion become sacrificial distractions, serving as easier prey for predatory insects that might otherwise eat their still-living conspecifics. Meanwhile, the strongest males mate with as many as a hundred females each before their bodies shut down and they share the fate of their less lucky rivals. When all is said and done, the females drift lazily back to the forest below, holding their wings in a half-furled position so they act as parachutes. After a long day of high-intensity flight, they must save the last of their energy to find a safe source of water to lay their eggs. They congregate around lakes, puddles, streams, and phytotelmata, depositing the next generation before keeling over. In some places, their bodies can be swept downriver and wash up in massive piles, attracting hordes of normally solitary insectivorous vertebrates.