Hi All,

I've long been curious about why colonies in the North tend to build up
larger during the summer than colonies further south, as well as appear to
decline more quickly in the fall.  Our discussion yesterday gave me a
clue.  I had previously investigated this by looking at daylength and
weather conditions, and determined that bees in Canada didn't necessarily
have more foraging hours per day, due to wind and temperature.  But
differences in the daily change in hours of sunlight near the equinoxes is
striking.  Note the differences in slopes of the lines in the graph below
around the equinoxes.


*Daily change in day length*


   - ·       At 55° N around April 1st, days are getting longer by about 5
   min/day
   - ·       At 45° N around April 1st, days are getting longer by about
   3.6 min/day
   - ·       At 35° N around April 1st, days are getting longer by about
   2.5 min/day
   -       By June 21, there is zero change per day, and then days start
   getting shorter, although colonies continue to grow​

Kefuss's findings on the apparent impact of daily change in photoperiod
suggest that this may be a reason that package bees taken to Canada build
up at such amazing rates.

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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