Strange Filter Situation Power Query

Thank you so much for your fast response! In my case, I am using power query with an Excel workbook and it looks like you are referencing a JSON object. Would I add your code like below if I wanted to use it with my Excel table?

let
    Source = 
          Table.FromRows(
               Excel.CurrentWorkbook(){[Name="Table1"]}[Content], 
               let _t = ((type nullable text) meta [Serialized.Text = true]) in type table 
              [#"Insect ID" = _t, 
                    #"Insect Description" = _t, 
                    Start = _t, 
                    Finish = _t, 
                    #"Insect Value" = _t, 
                    #"Want to Keep this Row" = _t]
          ),
    #"Added Custom" = 
        Table.AddColumn(
            Source, 
            "Single", 
            each 
                let s=Table.SelectRows(
                    Source,
                    (k)=>[Insect ID]=k[Insect ID]
                ) in Table.RowCount(s)=1 
                    and s[Insect Description]{0}="Caterpillar"
            ),
    #"Filtered Rows" = 
        Table.SelectRows(
            #"Added Custom", 
                each 
                    [Insect Description] <> "Cocoon" and 
                        [Finish] <> " " and 
                        ([Insect Description] <> "Caterpillar" 
                            or [Single] = true
                        )
            )
in
    #"Filtered Rows"

I did notice that I got the below error when I used this code. What would you recommend?

"Expression.Error: We cannot convert a value of type Table to type List.
Details:
Value=[Table]
Type=[Type]"

When I asked it to show me the error, it showed me the Source step.