Transovarial transmission of Rickettsia-like microorganisms in mosquitoes.

The wolbachiae found in Culex pipiens and the Tafahi strain of the A. scutellaris group are small rickettsia-like symbionts of the gonads. They are extrachromosomal self-replicating units that are vertically transmitted through the ovaries. Their presence in the only two groups of mosquitoes known to exhibit incompatibility, the fact that they are found in only the Tafahi strain, and the loss of incompatibility after removal of Wolbachia in C. pipiens are compelling evidence for the role that Wolbachia plays in incompatibility.