You listen to the soothing (and not at all annoying) buzz of <name>'s wings as he bites your opponent, extracts X damage worth of blood from it, and then injects it into you.
You watch with glee as <name> extracts X drops of blood from your enemy. Then you listen with barely-concealed horror as he squirts the blood into your ear.
<name> buzzes ominously while smiling with his wax lips
Arena Messages
When entered in a game of Hide and Seek:
<name> buzzes incessantly, making it very difficult to remain concealed.
Notes
Damage ranges from ceiling(Z/2) + 1 to Z + 3, where Z is the weight of the familiar.
The amount of HP you heal is X*2, with a bit of variation.
Specifically, you heal HP equal to a random number between X*2-floor(*X/5) and X*2+floor(*X/5).
The healing is triangularly distributed around X*2.
It acts 30% of the time, and always steals a minimum of 2 hit points.
It can act even after you deal a monster enough damage to kill it.
The mosquito acts after your attack, but before the monster's attack if any. This means that any healing is added to your HP before you lose any from the attack. The benefit is that one can be healed of damage before being knocked to 0 or less. The drawback is that if one is at or near full health and the familiar acts, the HP that would be over max are lost BEFORE you lose health from the monster.
Prior to the trivial update on February 25, 2014, the amount of damage dealt was between floor(Z/2) - 3 and floor(Z/2), where Z was the weight of the familiar. Also, HP healed by the mosquito was equal to the damage it inflicted.
References
The last line in the haiku is a spoof off of Budweiser's well-known catchphrase, which states that "This Bud's for you".