Winter vs Summer Colony Loss

I was surprised last year when a large number of my colonies lost their queen in early to mid summer.   Luckily I recognized the loss and was able to take remedial action.   Recent data has shown that summer colony losses are climbing while winter losses are decreasing.  Winter losses have usually been associated with varroa and tracheal mites.  One could speculate that mite treatments, hygenic bees and natural selection may be having a little success in the fight against the mites.  The rise in summer hive losses is still disturbing.  Do to the fact that summer losses have not been tracked until recently makes speculation on a root cause just that speculation.  It will be interesting if data from the European Union, which recently banned neonics, will show significantly different results.