From the games packaging

"The great human war of 2017 has nearly destroyed the Earth. Only a handful of simple creatures (mainly hardy insects) survive, and even they suffer severe mutations. The incredible radioactivity and chemical poisons dumped into the atmosphere were absorbed and integrated into the defecse system of the harmless Minimus Problemus beetle. Now equipped with a poison spray (and resembling very much a bug spray can of years gone by), the mutant Spraybuiis Toxicus beetle with its disticint orange color is your fiercest enemy."