I would appreciate some ideas about why I've lost two hives of bees . . .

Despite fall treatment, only one of two hives made it through the winter
this year.  This hive was looking good all spring.

Early summer I caught a swarm and re-started a second hive.  I noticed at
the time that #1 didn't have nearly the number of bees coming and going as
it had.  I didn't open it at that time.

One week after installing bees in #2 I opened it back up, re-installed the
other five frames, found good brood pattern and a nice fat queen.  They
looked good.  I also noticed no activity in #1.  Opened it up and it was
empty - no bees, no honey, no pollen.  Put that hive in storage.

I went on three week vacation shortly after that.  Came back to find the
same situation in #2.

Why am I loosing bees?  Is it way to late to order bees now?

John Taylor
Southeast Missouri