I’m back! I’ve wanted to do a headcanon for reformed changelings since I did Chrysalis, as well as work out changeling life-cycles to my liking. So here we have both Thorax and Pharynx!
 

 
The changeling life-cycle has three different stages. the larval stage, known as grubs, are small, not terribly mobile, and are ether adorable or horrifying, depending on who you ask. Thorax was shy and quiet, even as a grub, and often got overlooked for his louder, more aggressive sibling.  
Pharynx is special. He was born out of the same clutch of eggs as Thorax, but where his brother is a standard drone, almost indistinguishable from any other in the hive, Pharynx is a rare mutation known as a unique changeling. Unique changelings have a different appearance, and sometimes special abilities when compared to other drones. There are usually only one or two in a hive at a time. Ocellus is another unique changeling.
 
 
When a grub has absorbed enough love, they form a cocoon around themselves and undergo their first metamorphosis. Several months later, they emerge as a juvenile. Juvenile changelings have a black, dull carapace, and their chitin is brittle, leading to frequent chipping and cracking. In spite of the name, juvenile changelings are essentially fully grown in all ways but one. Unlike pony children, who have to spend ten to twenty years growing to their full size and developing an adult brain, changelings emerge from the cocoon in fully developed. They are, of course, lacking knowledge and experience, but for the first year or so after leaving the cocoon they learn incredibly quickly. Ocellus, in spite of having the intellectual development of a pony teenager, is just barely two years old when she attends Twilight’s school.
 
One thing that juvenile changelings can’t do is reproduce. That is only an option after going through a second, magically powered metamorphosis. The adult form of a changeling is brightly colored, and individuals will look very different from one another.  
It is technically possible for a changeling to remain a juvenile for their entire life. Chrysalis, in an attempt to control her hive and keep them from growing large enough to split off and form a rival group, suppressed the knowledge of the second metamorphosis. All of her subjects remained in their juvenile form until Thorax accidentally rediscovered it.
 
 
Queens are a bit of an exception to all of the above. Royal changelings have powerful magic. An adult queen, or even a juvenile with enough love stored up, can stand on equal footing with an alicorn. But this means that they require much more love to grow. To even produce the egg of a queen in the first place requires a massive outpouring of love magic, the likes of which is rarely found. After undergoing the first metamorphosis from a grub to a juvenile, a queen will grow to her final size at a rate much more comparable to a pony child. She will still learn a bit faster than a pony, but her mental growth is much slower than a drone. At the end of the process though, a queen is a powerful force to be reckoned with.  
A queen changeling is capable of reproducing even in the juvenile stage. This helps to keep the hive alive, even in harsh times when there isn’t enough love for normal drones to become adults and reproduce. The second metamorphosis of a queen is a difficult, magically taxing affair, and surprisingly few hives ever manage it. Chrysalis herself never gathered enough love to trigger it. Perhaps that is why she attacked Canterlot.
 
Or perhaps she had something else in mind.