Additionally, sexual antagonistic co-evolution can be the cause of rapid evolution, as is thought to be the case in seminal proteins known as Acps in species of Drosophila melanogaster.
Consistent with the arms race theory, DNA analyses reveal a two-fold increase in Acp divergence relative to non-reproductive proteins.
In the family Tingidae, pseudospermatheca are located at the base of the oviduct and are hypothesized to have functioned as spermatheca at one point in time.
In Drosophila species, a large group of enzymes known as serine proteases have been associated with female sperm storage organs (most notably, the spermatheca) through genetic sequencing and analysis.
[9] This would result in females choosing for males that can overcome these digestive enzymes, whether through genetic variation or physiological ability to produce greater quality or quantity of sperm.
In the case of water striders (genus Gerris) males will harass females and try to grasp them by chasing and lunging at them.
In seed beetles, a positive correlation exists between the degree of harmfulness of the male's genitalia and the thickness or reinforcement of the wall of the bursa copulatrix in the female's reproductive tract.
[citation needed] Male bed bugs have a unique way to copulate called traumatic insemination.
Female bed bugs have also evolved physiological by the presence of phagocytic cells in the mesospermalege that ingest sperm after mating.
[13] In females, genes associated with long development time lead to high fecundity and mate immediately upon eclosion.
This discrimination is reminiscent of the Fisherian runaway model, as females may choose for long tails based solely on inherited desirability, and would want to pass on that trait, which would improve the sexual success of their male progeny.
This also could be an example of the “good genes” model of sexual selection, as correlations have been found between sperm tail length and the physiological condition of the male.
[citation needed] In the case of the Neriid fly, Derocephalus angusticollis, males have been observed to have coevolved to have a flexible aedeagus.
In this species females have coiled oviducts that lead to the spermatheca that in turn make it hard for males to reach the area needed to release their sperm.