Three types of ovaries are found among insects. The panoistic ovary appears to be the ancestral type. Here, all oogonia (except stemline oogonia) are eventually transformed to oocytes. In meroistic ovaries, both oocytes and nurse cells (q.v.) are generated. These may be organized within the ovariole in two ways. In the polytrophic meroistic ovary, the nurse cells and oocytes alternate along the length of the ovariole. In the telotrophic meroistic ovary, the nurse cells are restricted to the germarium and are connected to oocytes in early stages of their development by cytoplasmic processes called nutritive chords. Panoistic ovaries are found in insects belonging to the more primitive orders (Archeognatha, Zygentoma, Ephemeroptera, Odonata, Plecoptera, Phasmida, Orthoptera, and Dictyoptera). Polytrophic meroistic ovaries occur in the Psocoptera, Phthiraptera, Hymenoptera, Trichoptera, Lepidoptera, and Diptera. Telotrophic ovaries occur in the Hemiptera, Coleoptera, Raphidioptera, and Megaloptera.
Subjects: Genetics and Genomics.