A time of need, A storm, and the oddest pairing was born
There is an odd thing that happens when the very complex epigenetically triggered DNA of a Chomper is pressured into choosing a form that doesn't respond to the known types: Gluttons and Savages. A young Chomper just out of the cocoon assesses its surroundings, and as everyone knows, begins to morph into its final form based on the availability of food. But the DNA had evolved over millions of years to become the apex predator which terrorizes villages throughout the world.
There was a time, however, long since switched down to recessive gene memory, when the Chompers' distant ancestor had to live by its fight-or-flight instincts. Somewhere buried deep in the twisting code of this horrible terror, was a frightened little animal, which went through a period of sharp-beaked predators who tore into the soft bodies, ultimately erasing a soft-skinned ancestor from all record; but leaving behind the hardy shelled creature we fear today.
Through a long and storied journey, this became the egg-shaped creature known in the forests today. But it is hard, and this shell is heavy. It came to pass, that food by predation was too energy intensive. The proto-chomper was, once again, in danger of starvation. And so they did starve out; save for a few who's sparse eating and sedentary life left them mottled and covered in the shade-like splotches which prevented their demise. And it was during this vulnerable period when something magical happened.
One particular bird, in a far off island, can see only in blue, or black-and white. This bird had a habit of protecting its nest fiercely. When one egg is out of place, the bird rails and puts on a frenzied show while restoring their home to order. This bird was carried aloft during a terrible storm, and found itself in the forest with the proto-chomper, who at this stage was almost indistinguishable from the agg of this bird. And so a love-ate bond was formed, where birds would spot a proto-chomper out of its place, and carry the hard little animal up into the tree to settle alongside the other eggs.
Now, this starving and feeble proto-chomper seemed to have landed square into the best opportunity ever, as breakfast was provided by these feisty and prolific birds. Once in a while, when the bird was off to find food, the proto-chomper would break through and consume one of its unhatched step-siblings. This arrangement worked well until the real eggs hatched, and the proto-chomper had an unconvincing look about it when it came out of the shell. So it learned to flap its small vestigial arm-like appendages (what their cousins eventually turned into the tube-like appendages) to mimic the flailing wings of its nest-mates. Mom didn't understand why her child had no head, but just dropped the food on the proto-chomper and decided to let nature take its course. She would not be to blame at least if her ugly child died.
And so it was that this variety of chomper found a home in the nest of a bird, and would take the food given by the mother, and when she was out, feast on one of the nest-mates, flapping its little arm-flaps like mad to get more food from mom.
Over time, the arm-flaps which could not pull the proto-chomper out of a nest naturally perished, as they could not find a mate. But the stronger ones had muscular arms which could pull themselves out of the nest, and drop themselves onto the forest floor.
Mother bird of course would raise her fit on returning and pick the creature back up. This left just enough time for the proto-chomper to execute its bizarre contact-less mating ritual, leaving a scent trail where its eggs would be buried, that a mate would find and fertilize. Larval proto-chompers were subterranean ambush predators until they consumed enough calcium to develop their shells.
It was this dropping from the nest, and being hoisted back up, which allowed proto-chompers of this clade to gain an advantage by gliding further away from the tree. Traveling away from the nest got them access to more buried egg sites, and so the proto-chompers who merely dropped to the ground were bred out of the pool.
Dropping and gliding was a very low energy activity, and having the mother bird to return them to the nest made life very easy. Easy, that is, except that you must recall, these were the predator ages. Proto-chompers were still tasty treats to many forest creatures. Some of them were quite clever, and the slowest proto-chompers would become food. But there was an explosion of genetic alteration at this point, which may be tied to a deposit of polonium which plunged from the earth after a tectonic shift. There were very common birth defects imparted from the proto-chompers' subterranean larval stage, which manifested into an explosion of diversity.
As nature has a habit of doing things, most sub-species from this age simply became food and were lost to all history. But of all the wing and leg and coloration varieties their DNA happened upon, a dominant young male found his arm-flaps now had the engorged muscles needed to lift himself up off the ground. This little proto-chomper was happy to sew his seed all about the forest floor. And it was this one, very lucky little creature who gave birth to generations of chompers who could take themselves to the air; albeit with very little grace.
As a most fortunate part of their design, being able to travel the forest for egg pits, got them access to as many bugs and small creatures that they could ambush as well. But what was more amazing, was how this little egg kept its relation with the birds. As long as the mottled blue casing remained, the mother bird would diligently bring her wayward child back into the nest, safe from ground predators. Now, these flying proto-chompers became symbiotic with the birds, and instead of eating their prey, they stored it up, and left it on the nest floor for the mother bird.
What was the purpose of this little gift to the bird? Well, it was a little more than just a morsel of food. The proto-chomper had partially digested the creature, leaving a sweet and syrupy enzyme on it, which was also partly fermented by the natural gut flora which have taken up symbiosis with the proto-chompers. The snack was sugary and slightly inebriating from the fermentation. The mother bird who consumes this morsel, in essence, gets "the munchies," and has to go out for more food. She eats more than her fill, and regurgitates the excess to the nest occupants. Of course, all of that eventually gets to the proto-chomper.
After a time, more diversity came to these creatures as territorial bird families created a postzygotic barrier, and proto-chompers inherited their symbiotic host bird's territory limitations as well as their diet. This lead to another explosion of allopatric divergence in the little flying eggs. And that final era or exploratory modifications is how the proto-chomper turned into the apex predator it is today, the Dropper.