>    Do any of you know of evidence that may support (or not) the notion that
>    the first crossing of un-related, low-aggression lines often results in
>    high aggression, which then dissappears (regardless of selection) in
>    subsequent generations.
 
Well a data point of one, a hive of very nice Midnite bees I have swarmed
and the new queen and whatever she mated with (possibly the Buckfast hive
next door or another Buckfast hive in the area) has produced some of the
meanest bees I've dealt with.  I don't know about the result of the next
generation; I plan to replace that queen.
 
-Mike