GERMARIAL DIFFERENCES AND THE PRODUCTION OF APHID TYPES

¹ Department of Zoology, Michigan State College, East Lansing, Michigan

The areas of the center cross-section of adult germaria of parthenogenetic female aphids producing different types of offspring were measured and compared. From this comparison it is evident that the center cross-sections of the germaria of male-producing wingless parthenogenetic females are larger than those of wingless females producing parthenogenetic females, and these in turn are larger than the cross-section of winged female germaria. All winged females have the same cross-sectional area whether they are producing parthenogenetic or gamic females.

A comparison of the volume of the nurse cell nuclei shows that the nuclei of gamic female germaria are larger than any of the others; those of wingless females producing males are smaller than the gamic nuclei, but larger than any other parthenogenetic nurse cell nuclei. The wingless and winged females producing parthenogenetic females have nurse cell nuclei of the same size, while the nurse cell nuclei of winged females producing gamic females are the smallest of all.

A correlation of the nurse cell nuclear volume of winged-wingless intermediates with the embryos contained in the ovarioles supports the thesis that size of nuclei and type of young produced are interdependent. Those intermediates that contained gamic embryos have the smallest nuclei; those with the next in nuclear size have both parthenogenetic and male embryos. The largest contain males only or males and gamic eggs.