I am often asked what cold weather does to insect populations.  It depends on the insect, the stage it is in and where it is located on the tree.  For moths such as citrus leafminer, the pupae survive, but many of the larvae inside the mines of tender flush leaves are killed as the flush is burned by the cold.  For California red scale, the younger instars tend to die off, leaving mostly the adult stages.  Citricola scales are in the 2nd instar stage deep inside the tree infesting twigs and experience very little mortality. Earwigs are deep in the ground waiting out the cold.  Asian citrus psyllid immatures would be killed by extended cold periods, but the adults would survive the cold and feed when the temperatures warm during the day. I guess the answer is that even in a freeze year, the cold never gets them all!