Morphological changes in female reproductive organs in the African monarch butterfly, host to a male-killing Spiroplasma .

We showed that although the general morphology of the organs is conserved in , female genitalia vary in size and shape between and within populations. The virgin females have smaller organs, while the same organs were expanded in mated females. Females from highly female-biased populations, where the male-killing is prevalent, also have a larger area of their bursae covered with signa structures. However, this pattern occurs because a larger proportion of the females remains virgin in the female-biased populations rather than because of male depletion due to the symbiont, as males from sex-ratio distorted populations did not produce significantly smaller nutritious spermatophores.