Instead of traditional castes, why not go with castes adapted from social insects?
Minims Represented by fingers. Once the smallest workers, used for pest control. Later they took on jobs like chimney-sweeping and sewer cleaning. Over time, their role changed with the rise of technology. Now they are "applied technicians" who replace parts on those 1km high microwave towers and so on. They also deal with things like hydroponic maintenance. They are noted for their ability to hyperfocus on a task for long periods of time without boredom.
Minors Represented by hands. The most common of the working castes and are a trade-off being size, strength, and requirements for clothing and food. They are relatively flexible and can do a wide variety of tasks. Most modern rank-and-file "city" jobs would be performed by Minors. With the advance of technology, they also are used as soldiers. They are marked by a lack of curiosity and have anterograde amnesia, which prevents them from creating new memories. Typically, they are raised and educated in their future task until about age 20 learning everything they need to, including how to go to their jobs and how to get home. At age 20 or so anterograde amnesia cuts in. This prevents them from getting burnt-out on their jobs, which tend to be repetitive but necessary.
Majors Represented by the arm. Noted by for their large size, stamina, strength, and silent loyalty. Once they were used as soldiers, fieldhands, and beasts-of-burden. They're still used for tasks that require strength and as soldiers. Normally, they are dull and content doing anything they're told. Under certain stimulus, they become hyper-aware but still loyal. Majors are able to coordinate with other Majors as well as emitting a pheromone that makes Minors obey them and thus become "NCOs" leading units of Minors into combat.
Mediae Represented by legs. Once scouts and foragers, with technology they became hunters. They are noted for their high awareness, curiosity, and a high sense of self-preservation (something missing from the lower castes) - a scout needs to report back more than fight well. They usually have jobs require to wander a lot, such as couriers and troubleshooters. They have a highly developed ability to sense when things are not going well; their primary job is not to solve problems, their job figure out there's a problem in the first place so that more specialized castes become aware of it. They are marked by a high degree of intelligence and perception, but actually have pretty short attention spans but a strong sense of duty.
Drones Represented by the mouth. Once the breeding caste, at some point, the species remade itself. Drones are Mediae who have eaten the "royal jelly" which causes mutations. They are more intelligent and posses specialized voiceboxes and pheromones that the lower castes recognize as "authority." They are represented by the mouth instead as their most important job is to give orders to the other segments of society. Workers normally do not require "managers" as we think of them: they do not require oversight. However, if something has gone wrong and workers can no longer do their task effectively, they will mill around at a loss for what to do. This is when a Drone arrives, assesses the situation, and creates a new work plan.
Translators Represented by eyes. Translators are Minims who have eaten the "royal jelly" which causes mutations. Translators have greater intelligence and curiosity and posses the specialized voiceboxes and pheremones of Drones, but lack the inclination to give orders. Instead, their job is to go out to an area where a persistent problem has been identified, gather as much data as possible and return to the thinking castes. Their "authority" is used to question workers at the site or to redirect them to help the Translator gather data. Once they have finished data-gathering, they can feed the information in a way that the thinking caste understands.
Brain Represented by the brain (oddly enough). Brain caste were once the queens and kings of the hive. Since the species redesigned itself, its ability to think has increased and the reproductive role is secondary to having brain function which makes the society run more efficiently. Brains are all highly educated but are hyperfocused in a particular area so are hard to distract. Their focus tends to be abstract science and engineering problems or macro-scale social problems. They'll ignore a blazing firefight going on around them to continue their research. They require data fed to them in a certain fashion for them to recognize it so they can interrupt their own projects and research to work on a new task or address a crisis. They are, like their ancestors, too precious to move or expose to possible danger so are immobile. They use Translators as their senses to gather data. Once they have gained data, pertinent specialists gather and discuss the problem, constantly acquiring more data and coming up with solutions, refining them as more data comes in, until a satisfactory solution is achieved. If a problem goes on long enough, it will become a semi-permanent area of study and new Brains will replace the retasked Brains in their old roles.
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I might have to use that entire concept in another spot.
