Can anyone share their experience with absconding of well established
colonies?  What causes do you see most commonly?  What does the comb look
like afterwards?

I just lost two well-established colonies in what appears to be a mass
absconding.

These are kept next to each other in long hives (like those discussed in
the thread on alternative designs which reduce lifted weight) with screened
bottoms, with a volume equivalent to 3 deeps.  The hives were not
overcrowded - if translated to Lang terms probably 15 and 20 full frames of
bees, respectively.  One was from an April swarm, the other an April split,
both were queenright when last inspected and had good laying patterns.
 Stores were adequate, though no surplus was harvested.  No history of
disease or pest infestation. Hives are in full sun.

We had almost two weeks of abnormally high temps (100+ daytime with a peak
temp of 105, tying the local all-time record, nighttime in the upper 70s).
 This was followed by a cool and rainy week, however the local dearth
effectively started two weeks early.  Last week I noticed some robbing
activity on both hives (bees trying to enter but not knowing where the
entrances were, tussling at the entrances) and reduced the entrances.  Very
mild robbing compared to some instances I have seen in the past.  Robbing
stopped but the following days forager traffic dropped off sharply.
 Yesterday found both hives to be completely empty.

On inspection, hives were both completely empty of stores but there were
some differences.  The stronger hive had a solid layer of dead bees on the
bottom (not enough to account for the whole population) and some ripped
comb.  No evidence of brood.
The weaker hive had very few dead left, no signs of robbing, but did
abandon some capped brood.  The frame with some brood looked extremely
strange - dead pupae were standing straight out from inside their cells as
though they had burst through the capping - the capping had not been
removed.  Some adults appeared to have hatched after the colony absconded,
and these looked very sick, abdomens pale, soft, and undersized, having
trouble walking.

Can anyone comment on likely causes?  Are the strange pupae and adults
relevant?  Does it seem more likely that robbing occurred before or after
absconding?

Thanks for sharing your experience.
Catherine

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