Old saying re bees on the syrup
Bees are very funny cos they walk across honey ,
Which must be very tricky cos honey's very sticky.
The bees are able towalk across the miniscus of the syrup , the surface tension supports them .
re wasps in syrup or hive , you supers are like as not wasp sealed , they often find away in throiugh badly fitting lids , broken corners or bad fitting supers , up through ill fitting /damaged hive floors as well as getting in through the front door.
I used only tray feeders on my fifty hives as it was so easy to pump 2 gallons of syrup at a time into them .
The tray feeders are designed so the only way into the feeder is up through the hive past all the bees.
The bit about reducing the hive entrance with a block of wood or foam strip is sound advice , I used to have a hive block for eachb hive ... a strip of slightly wedgeshaped oak that just fitted the entrance of the hive
One face had six double entry points .... rotate it 90 degrees and there was only one gap of 1/2 wide .
I used the six slot side once I started feeding and put a mouse guard on . After feeding up stopped around mid November I turned the block to one hole & fitted the mouse guartd to make the hole as central to the slot as possible to allow bees out on cleansing flights
If you do this sort of operation do ensure that the top vent in the hive lid is clear so there air can flow easily and it is not blocked with dead bees etc or propolis . or else your likely to get a sweating dying hive on your hands.
There is a type of feeder that mimics a hive frame . it has sides of hardboard or plywood and it is filled from the top and placed directly in the outer edgee of the brood box or the super immediately above the brood box.
whilst it's a bit late to do this for this year It can be very useful to overwinter hives on a brood & a half with the queeen excluder above the top super of the brood & a half set up.