Sorry for my late reaction. Your question does make me to think very long.

Summon Mosquito is a hidden skill. You can call the mosquitoes with it and attack the enemy. But it is not for a warrior or better say "fighter", but for a mage.
All of the hidden skills of earth are magical skills. And WIS 48 is already enough for a fighter. I would to say that it is not worth, because the physical skill Scurry Beating is much stronger than Summon Mosquito.

But I don't forbid you to get the hidden skill Summon Mosquito, if you like it, then get it. Of course it needs 10 WIS more, so it means 4 levels more, then you have a strong magical skill. It would be very handy against wind users with Vanish and users who are protecting by Stone Wall. And the greatest of all is that it doesn't make you a Hybrid, because it doesn't recommend INT to get Summon Mosquito.

I hope that my answer will be pleasure you.