How do dilatations form in mosquito ovarioles?

Ovariolar dilatations have been used to estimate parity status in mosquitoes for over 40 years. The theoretical basis for this parity-diagnostic method, which was established for mosquitoes by Polovodova 1, has been challenged by a number of Russian researchers. The findings of this new school of researchers have elicited little response from those currently using the method outside Russia, except for a recent paper by Hoc and Charlwood2. This has stimulated Andrew Fox and Reinhart Brust to review the formation of ovariolar dilatations here, and compare what they term the Old and the New Schools. Although the basic application of Polovodova's method is unaffected by the premise of either School, a clear understanding of ovarian dynamics is needed to understand the method and its limits.