Insector X (インセクターＸ) is a 1990 side-scrolling shooter developed by HOT-B for the Sega Mega Drive, with HOT-B themselves publishing it in Japan and the Sage's Creation unit publishing it in the US. It is a port of the 1989 arcade title of the same name, which appears to have been meant as a followup to Cloud Master.
The game has the insect-like main character, Kai, going through a number of nature-based and cave environments. The player can collect a variety of powerups and weapon upgrades to defeat oncoming enemies and bosses. The plot is fairly simplistic and ultimately involves defeating the dark ruler queen, freeing the insect world from her power.
The game has a strange history. HOT-B were originally contracted by Taito to produce a game called Insector X for arcades. The Family Computer port is entirely credited to Taito, but the Mega Drive port is almost entirely credited to Hot-B, with a small mention on the back of the US box being the only exception. Our best guess is that HOT-B bought the rights to Insector X in 1990 and produced this Mega Drive version. A similar situation seems to have happened with the otherwise unrelated Fire Mustang.
The port itself has an even stranger premise. The original arcade game used cute graphics with cartoony expressions, as does the Family Computer port. This Mega Drive port, on the other hand, has an almost complete aesthetic overhaul, now with a more serious player character and enemy force, and a completely replaced soundtrack. At the same time, most of the basic mechanics are the same, and enemy patterns are almost identical.
The final retail version comes in 'June' and 'July' builds; differences are and release information is unknown.