Bee in More Detail

The cranium-like head arises from fusing several primitive segments together. The head carries four pairs of appendages, the antennae, the mandibles or the bee's jaws, the maxillae and the labium. In bees, these latter two fuse into the proboscis adapted for feeding on liquid nectar and honey. The head of a bee carries a pair of large compound eyes. Between these big eyes are three smaller eyes or ocelli. The head attaches to the thorax. The cavity inside the head joins the cavity inside the thorax, and the neck tube allows the esophagus, nerves, blood vessel, tracheae and salivary ducts to pass from the head into the thorax much as cables traverse a conduit. Internally, within the cavernous space of the head, two large bars of cuticle extend from the sides of the neck into the cavity supporting and strengthening the head.

Because the thorax contains, supports and supplies the powerful motors driving her wings and legs, muscles almost fill the cavity of the thorax. These muscles are the muscles of locomotion as well as those moving the head and the abdomen. Hemolymph flows over and around these muscles, as tracheae admit air from outside and convey oxygen directly to the cells of the active muscles. Functions of the thorax depend on mass, flight activity, and load, and especially complicated relationships between metabolic activity and size, and are highly regulated (Chapter 10).

Thorax muscles: Muscular systems in the thorax are tightly and conservatively organized, as any additional weight costs dearly in terms of fuel. Cut open a bee's thorax to see that it is almost completely filled with masses of muscle fibers. You can see these with the naked eye, but if you tease the muscles apart under a dissecting microscope, you will see that the muscles are compartmentalized into units. Each set of muscles has multiple functions. Half of the muscles in the thorax, a right and left mass, course down the center of the thorax from the head back towards the abdomen. These are the dorsal longitudinal muscles that attach to a complex set of hinges and upon contraction, depress the wings. Other muscles in the thorax forming almost half the total mass of muscle, course at almost right angles to this first set. These crossing muscles, the dorsal ventral muscles, are the elevators of the wings. Depressor muscles of the back also serve a double function as they also elevate the wings. Contracting depressor muscles of the wings elevate the back and turn the wings down. During flight and preflight warm-ups, the two sets of muscles contract and relax alternately (Ref: Flight).

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