Jungle spiders is an idea that has been seen many times in the forum ... and it is also a redundant idea having already two types of spiders.
The truth is that I have been contemplating the idea of a monster or animal that lived in the leaves, I like the idea of the jungle spider, but not as a spider.
Today I suggest a new type of mob: acarus.
Acarus would be bigger bugs, stronger and more resistant than spiders, but also much slower and much more uncommon.
These would have the appearance of a giant mite.
Its shape and texture could be inspired in real life red velvet bugs (that are basicallly giant mites).
This mean: acarus would have a shape similar to spiders, but with a little non-mobile head, and a more fat body (middle part) than the end rear (butt part).
Also, its legs will be more separated: two pairs of legs will be placed literally in the head (being one pair larger than the other), and the other pair of legs will be placed in the end rear (being, again, one pair larger than the other). Eyes would be placed to the sides of the head instead the front.
These also would have a similar texture, but red skinned, with orange legs, more little eyes and bigger fangs.
I've tried to create a techne model for shown how it could be, but I have had difficulties and I have not been able to finish them (I will upload them soon).
These mobs will be generated at jungles and roofed forests, with an abundance of one for each three or four spiders.
In other biomes will also be generated, but with a probability as low as the husk in non-desert biomes.
Acarus also can be generated over leaves of trees (at the night), attacking to the player falling from up.
Also, acarus could be generated literally inside leaves, I mean, big jungle trees and dark oak trees could have a little chance of drop literally an acarus mob when became unstable.
Then, a big jungle tree could produce until five acarus when cut down.
Attack, movement and behaving:
Acarus will be inmune to falling damage, that is a property needed for being drop from leaves or do ambush attacks over trees, also, these would be able to climb walls and will become neutral with sun light (minimal level 7) as spiders.
These mobs would be slow as zombies or slower yet, but would have a big life, similar to endermans (40 health points), and in case of touch the player will cause a damage similar to zombies (3 hp at normal difficulty).
Acarus will have an special attack, these will jump over the player in "charged attacks" (with charge time of half second), causing a damage similar to be touched by a blaze (until 6 hp at normal difficulty, 9 in hard) and pushing or throwing out the player until three blocks.
Obviously, due to be slightly uncommon and slow, these should not be a big problem.
When killed, acarus will drop 8 experience points, will have a chance of 50% of drop an apple, another 50% of drop red wool, and will have a chance of 33,3% of drop spider eyes.
Basically these mobs would be more meanly by its gameplay impact than by its drop, although will drop 1,5 times more experience than common overworld mobs.