Fine Structure of the Compound Eye of Mallada basalis (Neuroptera: Chrysopidae)

Abstract

The morphology of the compound eye of the lacewing Mallada basalis (Walker) was investigated by scanning and transmission electron microscopy. The optical superposition eye is composed of ≈600 ommatidia that are identical in both sexes. The length of an ommatidiumis ≈100 μm. Each ommatidium contains a lens covered with small corneal nipples, 4 cone cells forming a crystalline cone and tract, 2 principal pigment cells that encompass the crystalline cone, and 8 retinula cells (numbers 1–8). Each ommatidium is surrounded by 12 accessory pigment cells, some of which are located in the center of a triangle formed by 3 adjacent ommatidia. Thus, accessory pigment cells belong to part of 3 different ommatidia. The proximal part of the ommatidium is tightly enclosed by the tracheae. In dark adaptation, 7 retinula cells (numbers 1–7) are arranged in a circle at the tip of the crystalline tract. The rhabdomere of retinula cell number 7 lies at the proximal end of the crystalline tract, and number 8 lies at the distal end of the rhabdom column. All 8 retinula cells penetrate the basement membrane and continue as 8 axons. Each ommatidium shows the fused-type rhabdom that is of great advantage to spectral sensitivity. The fine structure of the ommatidia is further discussed in detail.