Mosquito is a minor antagonist in Soul Eater. He is one of Arachne Gorgon's servants. A very neat and formal person, Mosquito is one of Arachne's most loyal assistants. Though he appears to be an old man, he can assume more powerful forms by regressing to a younger state.
After Arachne's defeat for 800 years ago, where he was at the zenith of his power, Mosquito devoted himself to building up Arachnophobia. By the time that Arachne was revived, almost getting into a fight with Giriko when he destroyed his limo, Mosquito escorted his mistress to Baba Yaga where the members of their organization welcomed her. From there, Mosquito is charged with overseeing the development of the Moral Manipulation Machine, which is currently nearing its completion within a concealed location before the DWMA destroy it. Later sent to retrieve Brew, Mosquito battles Maka and the others before overpowering the group while in his muscular appearance from a century ago. But ultimately, the fight damaged Brew and made it useless. When the DWMA Students successful invade Arachnophobia, Mosquito ends up facing Death the Kid and Free when they infiltrate and enter a truce to team up against him. However, overpowered in his form from a century ago, Mosquito regresses to his long limbed speed form from 200 years ago.
But when both Free and Kid manage to hurt him, Mosquito regresses to how he appeared 4 centuries ago. From there, noting Kid's level of power as a Grim Reaper, Mosquito proceeds to torture him while proclaiming that Death is no longer fit to oversee the world and that Arachnophobia will in charge a new world created from Asura's madness. However, Kid ends up getting a power boost from absorbing Brew and Mosquito finds himself having trouble fighting the youth while Free continued the mission to destroy Lock. Realizing Arachne is in danger, Mosquito escapes to the control room where he gets into a confrontation with Noah and assumes his original form to kill him. However, Noah kills Mosquito and takes the villain's remains, a single bat, as a memento.
In the anime, Mosquito survives after Arachne's death and has a cameo in the ending credits alongside Giriko.