Help,Critter Alert.How to kill this red thing??

Das ist nicht mehr gut das wenn du trockenes ist das voll mit Spinnennetz

If you're going to be harvesting really soon, I wouldn't worry about them... if you're wanting to do something, grab yourself some Dr. Zymes Eliminator or some Spinosad.. both are organic (although Canada does not consider Spinosad to be organic for really weird reasons) and use as directed which is to mix and then spray both top and bottom of all leaves and get the stems and branches as well - which, at this point in the grow, is a massive task. These two products will kill the adult, larvae and eggs of any leaf sucking insect (spider mites, thrips, aphids, white flies) and either one can be sprayed right up to harvest. Always good to have one of them on hand! Personally, I wouldn't bother at this point because it DOES look like you're going to be harvesting relatively soon. After you chop your plants, make sure you thoroughly sterilize your tent and equipment so the little rat bastards aren't present for your next grow! Good luck!

At this late stage why worry? They won't affect this plant greatly and why spray something you are going to be smoking real soon?

They're red spider mites. Spider mites feed on chlorophyll. They disrupt the process of photosynthesis by destroying chlorophyll and it can cause starvation, and eventually death of the plant. Your going to have to get some type of insecticide to fix this or harvest it immediately, decide fast because they reproduce at a crazy rate.