Ommatidial Structure of the Adult Stonefly, Oyamia lugubris (MCLACHLAN) (Plecoptera : Perlidae)

The fine structure of the compound eye of the adult stonefly Oyamia lugubris (MCLACHLAN) is described and compared with that of the nymphal stonefly and other orthopteroid insects. Each ommatidium possesses a centrally-fused rhabdom and is of the apposition eye, eucone type like that of most orthopteroids with the exception of Dermaptera. Although eight retinula cells take part in the formation of the rhabdom, the rhabdomeres originating from the more distal four retinula cells are extremely short. In the cytoplasm of these distal retinula cells a large quantity of lipid-like material and cytoplasmic processes were noticed. Proximally, the rhabdom is of triangular shape in cross section and consists of the three rhabdomeres of the remaining slender retinula cells. An eighth basal retinula cell with a very small rhabdomere is present. The surprising paucity of screening pigment granules is noted.