The anatomy of the compound eye ofPeriplaneta americana L.

The large compound eyes ofPeriplaneta are covered with irregular rows of low relief facets (10μm high).Measurement of interommatidial angles show large variations in these angles for both horizontal and vertical planes. Trends exist, however, with horizontal interommatidial angles increasing posteriorly from 1.9 ° to 10.0 °, and vertical field angles increasing posteriorly from 1.0 ° to 4.7 °.The maximum composite field of view for each eye is 240 ° in the horizontal plane, and 198 ° in the vertical plane. This results in a dorsal overlap of 40 °, an anterior overlap of 65 ° and a posterior overlap of 56 °. Thus, the necessary anatomical arrangement is present for binocular vision.The eyes ofPeriplaneta are a very dark, uniform colour, and apparently lack pseudopupils. An alternative explanation of the pseudopupil phenomenon to that of Yagi and Koyama (1963) is given and it is postulated that virtually all insects have them, although they may not be visible.