@JeffH answered your first question, so I will deal with the second part. Supering at that point in the season is a little late in most climates for nectar flow. The main flow is over by mid-summer, unless you are in a tropical or subtropical area. That is the simple answer, however, there may be a lot more reasons, and you can use the search tool at the upper right to find hundreds of posts dealing with this. I will get you started with one I found:
