Today the weather was great for a day in the bee yards. I've got 3 good colonies one of which happens to be in front of my truck shop which basically faces due south, maybe a bit southwest. Today I opened up the hive body and all seemed well with no SHB found. This colony sits on a limestone gravel base with the nearest dirt 20' away. There is no shade at all for this colony.
My other 2 colonies are 1/2 mile from the first colony sitting underneath 2 trees each facing the east. Each of these colonies had a good population of bees with one of them plenty strong enough to split now if I had a queen. Both had SHB,with the colony of greatest strength having a severe infestation.

IIRC some colonies have less SHB populations when in full sunshine (no shade), it seems I read or heard.

Would the full sunshine factor be the sole reason for no SHB in front of my shop or could the gravel base have an impact on the SHB reproduction abilities?