Methyl 3‐chloro‐4‐methoxybenzoate, a new candidate semiochemical inhibiting copulation behaviour of Ixodes ricinus (L.) males

Females of Ixodes ricinus (L. 1758) emit several semiochemicals influencing copulatory behaviour in males. One of these candidate compounds, methyl 3‐chloro‐4‐methoxybenzoate, is emitted exclusively by engorged females, and shows a copulation inhibiting effect in males. In Y‐tube experiments, the synthetic analogue of this compound at a concentration of 100 µg/mL in ethanol, attracted males in only 25.6% of tests, whereas it repelled them in 74.4% of cases. However, unengorged females do not respond to this substance at all. The number of contacts between males and unengorged females treated with methyl 3‐chloro‐4‐methoxybenzoate (250 µg/mL in ethanol, 1 µL per female) decreases to 28% compared to a control level of 80%, and the percentage of copulating pairs decreases to 12% compared to control (49%) over 2 h. Possibly, a fertilized engorged female with mature eggs uses this semiochemical to send a signal to males indicating that another copulation is no longer needed.