well ive seen someone talking about this and i looked into it and its pretty crazy. look this up on google for yourself (Spinochordodes tellinii). the Spinochordodes tellinii is a parasite that has been recorded to be able to take control of grasshoppers and cause them to commit suicide. there are other accounts of other bugs being controlled but not as many as the grasshoppers. so i was wondering, not now but further along in evolution what if these parasites grew or gained new attributes to adapt to its environment. well look at the facts later in the future earth will have to reach its capacity and some animals, bugs, parasites may have to fight to survive just as the human nature has known to. well these creatures will adapt and there adaptions could threaten the human race. this is kind of like the movie the happening but with parasites as substitutions for plants but for all we know plants might have to adapt to survive considering humans might find a way to conserve oxygen without the need for trees, this would then threaten plants and they might counteract to save themselves. well thats it let me know what you guys think.