Thursday, December 30, 2010

The Compound Eye

The type of eye commonly found in arthropods, including many insects and crustaceans. A compound eye has a mesh like appearance because it consists of hundreds or thousands of tiny lens-capped optical units called ommatidia. Each ommatidium has its own cornea, lens, and photoreceptor cells for distinguishing brightness and color. Individual ommatidia guide light through a lens and cone into a channel, known as a rhabdom, which contains light-sensitive cells. These are connected to optical nerve cells to produce the image. The ommatidia are separated from each other by varying degrees of pigment.

The ommatidia are packed side by side into bulges that create a wide field of view. As each unit is orientated in a slightly different direction, the honeycombed eye creates a mosaic image which, although poor at picking out detail, is excellent at detecting movement.

Saturday, December 18, 2010

Shedding skin

The forest bug, Pentatoma rufipes, is a species of shield bug in the family Pentatomidae. It is a common and widespread species found in forests and woodlands worldwide. It is shiny dark brown with red-orange markings on its body and bright orange legs. It is shaped like an escutcheon-type shield, flat, and about 14 millimetres (0.55 in) long. Its distinguishing characteristic is a pair of plates extending forward from the shoulders at the front of its dorsal thorax.
The forest bug's main food source is any of several species of oak. It is a sap-feeder and uses piercing mouthparts to withdraw the liquid. It can also be found on other species of deciduous trees. The forest bug is also an agricultural and garden pest, as it will not hesitate to feed on fruit and nut trees. Occasionally it will consume other insects.
Adults lay eggs during the summer in the cracks of tree bark, and the larvae hatch the following spring.