This year (2008) Madeleine Beekman and Ben Oldroyd, two of the
foremost honey bee scientists, published a paper on the parasitic
character of certain subfamilies in the honey bee colony.

excerpts for review purposes:

Until recently, scientists
were burdened by the widespread view of insect
colonies as harmonious entities sharing
none of the strife that so often characterizes
our own societies.

Now that we have discarded most of our
historical baggage, the new facts are apparent.
Worker bees can be parasites of their
own society or those of their neighbors.

In this review we examine
these recently revealed instances of intraspecific
reproductive parasitism in eusocial bees.

We focus on different systems in which
worker reproduction is commonplace: intracolony
parasitism in queenright anarchistic
honey bee (Apis mellifera) colonies, parasitism
by Cape honey bee (A. m. capensis) workers in
colonies of their conspecifics A. m. scutellata
and in their own colonies.

Analyses have revealed the presence
of intraspecific parasites: reproductively
active workers that either have sneaked into
non-natal colonies or have managed to circumvent
the mechanisms that normally ensure
functional worker sterility.

Understanding
the ways in which these parasites avoid
mechanisms that are normally in place to prevent
the expression of selfish behavior gives us
an appreciation of the often subtle means by
which functional worker sterility is achieved.

Although at a collective
level workers agree that no worker should reproduce,
owing to the low relatedness among
subfamilies, the potential for worker-worker
competition is severe.

Workers therefore police
each other's eggs to ensure that no worker
breaks the collective agreement brokered by
evolution. As a result, intraspecific parasites
are only successful once policing has ceased
or if they manage to disguise the maternity of
their eggs.

-- 
"When Workers Disunite: Intraspecific Parasitism by Eusocial Bees"
Madeleine Beekman and Benjamin P. Oldroyd
Annu. Rev. Entomol. 2008

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