Abstract 1. 1. Lipid is stored in both the ovaries and fat body of female Leucophaea maderae during the 20-day period of oögenesis and is a major substrate for the developing embryos during the ensuing 2 months of embryogenesis. 2. 2. The lipid picture for the period of embryogenesis is characterized by a decreasing content of embryonic triglyceride and an increasing proportion of phospholipid. 3. 3. Both the fat body and ovaries (maturing oöcytes) are capable of incorporating labelled palmitate into glyceride and phospholipid. 4. 4. In vitro studies demonstrated the transfer of labelled lipid from the fat body to ovaries and it is likely that this takes place in vivo as well. The metabolic activity of the fat body is influenced by the stage of the reproductive cycle, particularly in reference to lipid metabolism. 5. 5. In vitro studies with active corpora allata suggest that one reason the juvenile (gonadotropic) hormone is indispensable for oöcyte maturation is its ability to enhance lipid synthesis in the ovary (maturing oöcytes) during oögenesis. 6. 6. These studies suggest that the juvenile hormone may act to depress the lipid synthetic ability of the fat body at this stage and thus make more substrate available to the developing oöcytes.