Get index of pandas series in data

I want to format a series of strings so that the index is somewhere in the string. Example series:

ser = pd.Series(['CT', 'NY', 'MT'], index=['Jessica', 'Eric', 'Toby'])
ser
Jessica    CT
Eric       NY
Toby       MT
dtype: object

      

        
        
        
      

    

Desired output:

Jessica    Jessica: CT
Eric          Eric: NY
Toby          Toby: MT
dtype: object

      

        
        
        
      

    

I've tried variations of this:

ser.apply(lambda x: "{}: {}".format(x.index, x))

      

        
        
        
      

    

but that doesn't work because it x.index

refers to the index method str

and not the series being iterated over.