std::thread from c++11 - execute class functions

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Let me past sample code:

#include <iostream>
#include <cstdint>
#include <thread>
#include <list>

class Item {
public:
    void Calculate()    {}
    void Merge()        {}
    void Send()         {}
};

int main()
{
    std::list<Item*> itemlist;
    for(uint32_t itemNum = 0 ; itemNum < 100 ; itemNum++)
        itemlist.push_back(new Item);

    while(true)
    {
        for(Item *itemOnList : itemlist)
            itemOnList->Calculate();

        for(Item *itemOnList : itemlist)
            itemOnList->Merge();

        for(Item *itemOnList : itemlist)
            itemOnList->Send();
    }

    return 0;
}

What i like to do is when program is run all time, for each item in list will be executed in diferent thread.

So for example:

for(Item *itemOnList : itemlist)
    itemOnList->Calculate();

Will run on maximum threads (std::thread::hardware_concurrency()), then when that ''Calculate'' function finish i like to call again same threads to do different job ''Merge'', then wait for all of them to finish, and call last one ''Send''.

I was think to do that o list for example:

std::list<Item*> calculateItems;
std::list<Item*> mergeItems;
std::list<Item*> sendItems;

Then create threads and assign ''list'' to make it work, so i will end up with:

3 lists + 8 threads for each list, that will do calculation all time. But problem with this concept is, that i need to finish one 'function' before i can call another.

What i have problem here is how i can manage this functions calls in multithreading way.