THE SIGNIFICANCE OF GERMARIA IN DIFFERENTIATION OF OVARIOLES IN FEMALE APHIDS

¹ From the Department of Biology, Wittenberg College, Springfield, Ohio

Winged parthenogenetic female aphids produce both parthenogenetic emale and gamic female aphids.

The ovarioles of adult gamic female and parthenogenetic female aphids differ primarily in the nature of the eggs developing within them and secondarily in the size and secretory activity of the germaria. Gamic female germaria are large and secrete much yolk; parthenogenetic female germaria are small and secrete little yolk.

The ovariole differences apparent in the adult aphids are also eident in the embryos. In parthenogenetic female embryos of a late stage of development the embryonic ovarioles already contain oöcytes and eggs undergoing parthenogenetic development while in the gamic female embryos of the same stage of development the germ cells have not yet entered the vitellarium. The germaria of parthenogenetic female embryos are smaller than the germaria of the gamic embryos of the same stage of development.

In both gamic and parthenogenetic female embryos the germaria are the first reproductive structures to develop.

The theory is proposed that determination of the ovariole type (either gamic female or parthenogenetic female) affects the germaria only. Each germarium, thereafter, controls the development of the ovariole to which it is attached.

Aphids intermediate between gamic female and parthenogenetic female aphids with respect to the ovarioles are described and analyzed to support the above theory.