Bosco Spider (多砲台掃討機 ボスコスパイダー Ta Hōdai Sōtō-ki Bosuko Supaidā?, lit. "Multi-Cannon Sweeping Machine Bosco Spider") is a boss in Contra III: The Alien Wars. It is fought at the end of Mission 2, Destroyed Highway.
Bosco Spider is a huge spider-like mecha armed with six round-shaped cannons, one mounted at the end of each of its six legs, and also comes with a mobile laser ray gun attached as a manner of tail. It is encountered at the end of the Destroyed Highway, and same as with the rest of the level, it is fought in overhead view mode. Its weak spot is a large red core located on its front.
It makes its introduction by falling from the sky and smashing onto the ground. Due to this boss's immense size, it may occupy a big portion of the screen for most of the battle. Its main method of attack consists in advancing toward the player while constantly shooting from the cannons mounted on its legs. Its secondary attack consists in shooting a laser ray from its tail cannon and then spin both the cannon and its whole body in order to cover a larger area. Each cannon can be destroyed separately in order to help alleviate the whole ordeal. Every time one of these is destroyed, it will leave behind a weapon powerup or even a bomb.
As more cannons get destroyed, Bosco Spider will resort to another attack where it will start spinning its whole body at great speed and then launch itself toward the player.
Once the mechanical monster has sustained enough damage, it will start jumping high in the air and attempt to land on the player throughout the rest of the fight.
While this boss may pose little to moderate threat at Easy and Normal difficulty levels, in Hard it becomes very dangerous as it gains enhanced mobility and performs all of its attacks at greater speed, with the end of the battle being a series of continuous stomps where the player must concentrate on getting out of its way while having little time to counterattack.
The Crush Gun is an overall good choice for this fight, as it deals the highest amount of damage and the explosions it unleashes remain in place for a short time, dealing additional damage while the boss slowly approaches.
In the Game Boy port, Contra: The Alien Wars, the Bosco Spider's behavior has gone through some changes; for instance, the boss itself does not spin around and instead the rounded cannons are the ones that spin around it. The tail cannon is not mobile, and instead of a laser it fires vulcan rounds in a spraying manner. In addition, the cannon itself is the boss's weak spot, and once destroyed, the whole boss will be defeated.