The retinula ( literally, " small retina " ) cells of the ommatidium of the compound eye contain areas from which membranous organelles of conceivable size ( rhabdomeres ) extend.
12.
In all arthropods, there is always a rhabdom below a crystalline cone, on or near the center of the ommatidium, and always aligned with the path of light.
13.
Light entering at an angle passes through the thin cross-section of the photoreceptor cell, with only a tiny chance of exciting it, and is absorbed by the pigment cell, before it can enter a neighboring ommatidium.
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The inner 90 % of the ommatidium contains 6 to 9 ( depending on the species ) long and thin photoreceptor cells in the case of some butterflies often abbreviated " R cells " in literature and often numbered, e . g.
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The infraorder Cucujiformia includes the vast majority of phytophagous ( plant-eating ) beetles, united by cryptonephric Malpighian tubules of the normal type, a cone ommatidium with open rhabdom, and lack of functional spiracles on the eighth abdominal segment.
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In true flies, the rhabdom has separated into seven independent rhabdomeres ( there are actually eight, but the two central rhabdomeres responsible for color vision sit one atop the other ), such that a small inverted 7-pixel image is formed in each ommatidium.
17.
In some species there is a complete separation . for instance, one way to tell adult " Bemisia " from " Trialeurodes " is that the upper and lower parts of the compound eyes are connected by a single ommatidium in Bemisia, while in Trialeurodes they are completely separate.
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:( ec ) I found a rather cute write-up at a quirky site . First it points out the obvious : an ommatidium contains only about 8 rhabdomeres ( photoreceptor cells-see [ http : / / cistron . ca / ommatidia . shtml here for the fruit fly example ).
