Greetings!
It appears that the word "caste" is being used in discussions
incorrectly. Caste does not seem to refer to perceived differences in
worker bees at all, but to the difference between the queen and the
workers. " Workers assume different roles in the nest as they age, a
pattern known as temporal polyethism." see below:

quotes:

A major product of the general scientific research into the ecology
of Apis Mellifera is a greater understanding of the honey bee's
"social structure" and population dynamics. In examining the
population of the colony, scientists have uncovered the existence of
a highly ordered caste system. The queen reigns at the top of the
caste, with the male drones and female workers below. ... The workers
are the second caste in the colony and perform many crucial tasks
within the hive. ... The male drones are the third caste in the
colony.

http://gears.tucson.ars.ag.gov/beepop/intro.html

* * * * *

Honey bees live in a caste system and are so highly specialized that
no individual bee, including the queen, is capable of living alone or
establishing a new colony alone. Adult honey bees consist of 3 castes
- queens, drones and workers. The queen is the only fully developed
female in the hive.

http://beelab.cas.psu.edu/P-gals/Gal3/Hymenop/hy09.html

* * * * *

Queen and worker honeybees (Apis mellifera L.) are both female, but
differ in form and function. In a honey bee colony there is one
queen, whose role is reproduction, and several thousand workers,
whose tasks are non-reproductive (cleaning, gathering food, cooling
or warming the nest, etc.). Both castes produce a characteristic
blend of functionalized 8- and 10-carbon fatty acids in their
mandibular glands.

http://www.sfu.ca/chemistry/faculty/Plettner/Bio.html

* * * * *

III. The caste system of the honey bee relegates individuals (drones,
queens, workers) into programmed roles from which there is no escape.

IV. The basis for caste determination in workers and queens has been
the subject of many studies. There is a worker to queen continuum
because intercastes can be created artificially and they are also
seen in nature, though rarely. Some theories on caste determination
follow:

A. Haydak hypothesized the quality of food the larva received had a
good deal to do with determining whether a queen or worker developed.
He also suggested hormones were somehow involved. B. Weaver believed
that the jelly fed to larvae might have a "determining substance"
incorporated into it. C. Shuell and Dixon suggested that nutrient
balance was important and shifts in this could determine caste
development. D. Dietz showed that moisture content was increased in
jelly fed to queen larvae, allowing them to consume more than
worker-determined larvae. E. Lensky found that sugar ratio of
fructose to glucose was important in caste determination, and that
juvenile hormone (J.H.) played an important role in the process.

http://bugweb.entnem.ufl.edu/eny4571/classificat.htm

* * * * *

In social Hymenoptera, the determination of sex is intertwined with
the determination of social role. For sociality to be effective, the
balance of workers and reproductives (reproductively able
individuals) must be modulated. Females develop into one of several
castes, each of which perform specific tasks. Different taxa have
different numbers of castes, and different degrees of caste
specification. In some groups caste determination is both reversible
and barely distinguishable on a morphological level, while in other
taxa caste differentiation is irreversible and marked by extreme
morphological differences. The mechanisms of caste determination may
vary widely.

Apis mellifera, the honey bee, has the best studied system of caste
differentiation. Differences in caste specific behavior have been
understood for many years (Michener, 1974), but recent molecular
studies have shed new light on the mechanisms by which it occurs. In
honey bees, the primary determination is between worker bees and gyne
(future queens). Gynes are given a special diet that activates queen
specific development. Workers assume different roles in the nest as
they age, a pattern known as temporal polyethism.

http://www.sccs.swarthmore.edu/users/99/mahowald/caste.html