Wednesday, March 20, 2013

Stingless bees

Bees with the necessary honey-storing characteristics to be exploited by humans for their honey belong either to the subfamily Meliponini that contains several genera of stingless bees, or to the single genus Apis, the honey bees, The stingless bees are  social bees that  store significant volumes of honey.  Their natural distribution is throughout tropical and subtropical areas of the world, and there are around 300 species.  They live in perennial colonies ranging from a few dozen individuals to many thousands.  Their social organisation, division of labour between workers and some of the physical structures of the adult bee (such as pollen baskets) are similar to the Apis genus of honey bee. 

However, their biology differs from honey bees in some significant ways.  For example, the feeding of stingless bee larvae is very different from the way that honey bee larvae are fed.  In stingless bees the cells are mass provisioned, which means that all the food the larva will need for its development is placed in the cell in one operation by a nurse bee.  One of the workers will then lay an egg (known as a trophic egg) into the cell.  The queen will be attracted to the group of workers laying eggs and will come and eat the egg, plus some of the food provision before laying her own egg into the cell.  After this the workers seal the cell so the larva can mature and pupate.  The queen will receive most of her nutrition in this manner.

Stingless bee cells are oval or round and are arranged in orderly groups or plates, which may be reminiscent of honeycomb.  Their nests can be found in cavities in trees or in exposed nests attached to tree branches.  Other species nest underground and may take residence in part of a termite's nest.  The nest is frequently divided into two parts - the brood chamber where the larvae are reared and, in some species, a special area for storing honey and pollen.  The nest is made of a waxy substance called cerumen, collected from resinous trees, and covered in a tougher wax known as batumen - similar to the propolis used by honey bees.
New nests are started by workers from an existing colony starting up a nest in a different site.  Eventually a young queen from the old colony goes to the new site with a few workers and gradually the colony builds up to become independent of the parent colony.  This arrangement precludes the rapid spread of new stingless bee nests to new areas, making them very vulnerable to habitat loss.  Female caste differentiation is different from the honey bee (which arises because of food quality).  Michener 2000, describes three different systems of queen determination.

1. A small number of queens are reared at the margins of the comb and the quantity of food supplied appears to be the controlling factor in queen development.
2. The second system uses clusters of specially shaped, well separated and well fed cells.
3. The third system uses no special cells but the small sized females produced mature into queens after hatching.

Mating occurs outside of the hive with the virgins entering into male mating swarms.  As in honey bees, males mate once and then die.

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