According to “Mother Earth News,” these young bees are orienting themselves to the entrance, a good sign the hive is healthy and queenright. Since we did a hive check on Friday and counted four frames filled with capped brood and many more partly full, this would seem to be true. And we only checked one of the deep boxes.
The robber screen is to help keep keep out potential hive raiders. Like the hateful Yellow Jackets we have in abundance. For more info on this behavior, go to https://www.motherearthnews.com/homesteading-and-livestock/at-the-hive-entrance-zbcz1408