OVARIAN DEVELOPMENT AND PARITY DETERMINATION IN CULISETA-MELANURA (DIPTERA, CULICIDAE)

A laboratory colony of Culiseta melanura (Coquillett) was used to foll ow ovarian development from emergence to oviposition and to validate t he accuracy of using follicular dilatations to age grade females. We o bserved no change in the size of the primary follicles in unfed female s from emergence to 3 d of age. Sugar feeding stimulated follicular gr owth and produced the following 3 types of ovarioles: (1) large primar y follicles that eventually developed into functional ovarioles; (2) l esser numbers of small primary follicles that developed small amounts of yolk after blood feeding but degenerated in the latter stages of de velopment; and (3) small primary follicles that did not develop yolk a fter blood feeding, exhibited accelerated growth, and became rogue ova rioles with multiple false dilatations. The yolk of the small primary follicles that degenerated after blood feeding was resorbed during sta ge IV of egg development, and the degenerating follicles resembled gon otrophic dilatations in the latter stages of the cycle. This process p roduced gravid females with some secondary follicles that appeared to possess a gonotrophic dilatation. Other authors have termed these arti facts false or agonotrophic dilatations. Degenerating ovarioles bearin g these artifacts were used to determine physiological age in blood fe d and gravid Cs. melanura. Nulliparous females in the latter stages of gonotrophic development have single false dilatations on degenerating ovarioles, l-parous females have 2 false dilatations on degenerating ovarioles. In unfed, nulliparous females, false dilatations can be dis tinguished from true dilatations because they are attached to secondar y follicles that are much smaller than the primary functional follicle s that fill most of the ovary. In blood fed and gravid females, follic les that support false dilatations always lack yolk. Rogue ovarioles a re unreliable indicators of physiological age and should not be used f or diagnostic purposes.