Around late February 1975, Mosquite was stationed on Mother Base for a planned inspection by the UAEA regarding supposed nukes. Having been informed, alongside the other MSF members, of the impending inspection, as well as the suspected reasons for the inspection, he also proceeded to keep his mouth shut about Metal Gear ZEKE.
During the inspection, however, he alongside Kazuhira Miller and some other MSF members heard an explosion, and then discovered that the "inspectors" were actually armed soldiers who proceeded to raid the place as Mother Base itself was sinking into the ocean, due to the struts being wired with C4. Ultimately, he alongside Miller were among the few who survived. Mosquite and other soldiers then helped Miller over to Morpho to escape. However, before he himself could board, Mosquite and nearly all of the remaining soldiers were shot dead. Big Boss, who witnessed his men's deaths firsthand, proceeded to attack the armed men until he ran out of ammo, grabbed Miller's hand and escape along with a single surviving MSF soldier just as the strut sank to the ocean.
Behind the scenes
Mosquite is a soldier who appeared in the ending to the main mission of Metal Gear Solid V: Ground Zeroes. Although he isn't named by any of the characters, he can be identified by the name on his backpack, which has the word "MOSQUiTE!!" on it.
The Piggyback Guide book for Metal Gear Solid V: The Phantom Pain erroneously refers to Mosquite as Mosquito. In addition, the names on their backpacks are slightly different, as the one in Ground Zeroes has an "e" on the end, while the one in The Phantom Pain has an "o" on the end.