Ability score increase: Your strength score increases by 2 and your dexterity score increases by 1. Your charisma score is reduced by 2. (+12,-4)
Negative ability score are not in the PHB and should be avoided.
Also, note that the Tasha's optional rules let you float these.
Next, Dex and Strength are the two least synergous stats in 5e. High dex means you don't need strength that much, as you can attack with bows/finesse melee weapons, and wear light armor for near heavy armor AC.
High strength means you can wear heavy armor, which ignores dex to AC, and attack with melee and thrown weapons.
Languages/Age/Alignment/Size aren't important to balance I don't think.
Darkvision: The dark corridors of the colony are your home. You can see in dim light within 60 feet of you as if it were bright light, and in Darkness as if it were dim light. You can't discern color in Darkness, only Shades of Gray. (+3)
I'd actually cut darkvision. It is too common, honestly. But it is a minor bump.
Speed: you have a walking speed of 30 feet and a climbing speed equal to your walking speed. (+2)
Climbing isn't bad.
Built-in armor: your tough exoskeleton makes you hard to harm. Your AC is 13+ dexterity. (+3)
This is reasonably strong. Even on a barbarian, you'd need 16 con to match this AC unarmored. And as equivalent to mage armor or +1 studded or a few class features, isn't nothing.
It does tend to make a dex-build for this race more optimal. Which makes the str boost less useful, outside of tasha's optional rules.
Ambush predator: You're proficient in the stealth and perception skills. (+4)
These are among the two most rolled skills in the game. It does sort of make sense for an ambush predator, but I might drop perception here and make it survival or athletics.
Ambush predators aren't good at spotting ambushes, they are good at setting them. Prey have better perception than predators.
Raptorial blades: your forelimbs have durable bladed appendages (finesse) which protrude from the forearms. Deal 1d6 piercing/slashing damage. (+6)
The wording here needs work.
Piercing/slashing, do you mean they can pick on each attack? There is no hybrid damage in 5e.
Is it an unarmed attack that does this, or is it a weapon?
Bug bite: the chitinous plates in your head hide powerful Jaws. Deals 1d4+strength of piercing damage. (+1)
This is strictly worse than the other natural weapon, unless you are holding items in your hands, and those are worse than your natural weapons, so you need to bite.
I'd rewrite this. Or delete it. If you keep it, it is noise, and worth 0 balance wise.
Always watching: You do not require sleep to survive. When you take a long rest, you must spend at least six hours of it in an inactive, motionless state, rather than sleeping. In this state, you appear inert, but it doesn’t render you unconscious, and you can see and hear as normal. (+3)
This seems more like a feature of prey, not a predator.
If you want to push the ambush nature, you could have a stealth torpor here. Add in a bit of hide in plain sight ness here somehow.
Like, you can hide against natural surfaces with no other cover or concealment over 10 minutes so long as you are motionless and not wearing armor. In this state, you are aware of your surroundings, and can take a short or long rest, blah blah blah.
This then lines up the built-in armor feature with your rest feature.
Ability score increase: Your strength, dexterity and constitution score all increase by 1. In addition, you can pick any one statistic to increase by 1 point, including your strength, dexterity or constitution.
Age: the Fehl-her reach maturity at 5 years old and live up to a maximum of 100 years.
Alignment: the Fehl-her strongly defend the importance of order as the most important thing to ensure proper functioning of their group, being usually lawful.
Size: a Fehl-her grows no larger than 7 feet tall, averaging at 6 feet, weighting between 160 and 180 pounds. Your size is medium.
Speed: you have a walking speed of 30 feet and a climbing speed equal to your walking speed.
Languages: you can speak, read and write in common language, as well as speak in the tremor-language of Fehl-her. Fehl-her is communicated by vibrating a surface you are both touching; it has a range similar to speech, but that produces noise as loud as normal speech. Using it silently reduces its range to the tremorsense of the communicating creatures.
Tremorsense: The dark corridors of the colony are your home. You have Tremorsense with a range of 15'.
Exoskeleton: your tough exoskeleton makes you hard to harm. When not wearing armor, your AC is 13+ your dexterity modifier.
Ambush predator: You're proficient in the stealth and athletics skills.
Raptorial blades: Your forelimbs are durable bladed appendages. When not holding an item in a hand, you can treat your hand as holding a as 1d6 light finesse weapon that deals slashing damage you are proficient in when making an attack.
Bug bite: As a bonus action when you are grappling with a creature or on your turn after you strike a critical hit with a melee attack, you can make an attack with your powerful Jaws. On a hit, you deal 1d4+strength piercing damage.
Ambush topor: During a rest, you can spend 10 minutes entering an ambush topor. If you are not wearing armor you blend into a natural background, allowing you to hide without any cover or concealment. You can stay awake and aware and rest so long as you do not move, and if spotted you appear inert. Being in this state for 6 or more hours replaces your need for sleep for that day.
Tremorsense is worse than blindsight, and at 15' the range is quite limited. It also evokes the feel of a creature living in tight corridors underground.
Making the language be a Tremor-language is fluff.
The bug bite still exists, and has impact. It isn't a huge one.
Athletics is designed to avoid synergizing with the dex-bias of the rest of the race at this point.
+1 to all physical with a floating point (which can go to mental stats) is more in line with Tashas. The tertiary +1 isn't all that useful if you allow full floating, and if you don't the lack of str/dex synergy in 5e makes that benefit weaker anyhow.
I reworded the blades so they are clearly using the weapon rules.