Well, I looked it up.
The mating behaviour of the hen flea Ceratophyllus gallinae is described and analysed. The sequence begins when the male accidentally collides with a female and his maxillary palps receive a contact-chemical stimulus. This sexually stimulating substance is present on the abdominal cuticle of both males and females. It causes the male to run and to erect his antennae. He then pushes against the female, who responds by running forwards, thus correctly orientating the partners. Tactile stimuli probably received by the receptors on the head lead the male to clasp the ventral surface of the female's abdomen with his antennae. The resulting tactile stimulation of the inner surfaces of the antennae allows the male to raise his genitalia to meet those of the female. Correct linkage of the genitalia is probably detected by the male's sensilium.
The sequence of behaviour shown by the male is a series of fixed acts each producing the specific stimulus situation necessary for performance of the next act. Absence of the required stimulus results in the behaviour reverting to an earlier point in the sequence. The integration of the sequence is thus under rigid stimulus control.
Owing to the complexity of the male's genitalia, many minutes elapse between pairing and the passing of sperm to the female. The chances of the fleas accidentally separating during this period are reduced by the male stimulating the female's sensilium and so inhibiting her movements.
