SEXUAL BEHAVIOUR OF THE SHEEP TICK, IXODES RICINUS (L.) (ACARI, IXODIDAE)

Abstract:
The pattern of pre-copulatory and copulatory behaviour of the sheep tick, Ixodes ricinus (L.) was studied. Male attraction to female and subsequent copulation operate under the control of pheromones. Both engorged and unengorged (questing) females emit volatile substances which attract males, causing their pre-copulatory behaviour. About 90.6-97.6 % of active males are attracted to engorged females in a four-arm olfactometer, whereas 76.4-78.3 % in an Y-tube olfactometer. Unengorged females cause positive reaction in 55.6-62.5 % of males in the four-arm olfactometer and 57.3-70.9 % in the Y-tube. Reactions of ticks from our laboratory colony were less intensive than of those from nature. The attracting substance was trapped in an U-tube submerged in liquid nitrogen and then deliberated into an olfactometer. About 86,7 % of active males were attracted with such trapped and deliberated attractant. This attractant probably plays the role of the attractant sex pheromone (ASP) in the sheep tick. A high stimulatory effect of semi-engorged females on male sexual behaviour was observed. The following steps of mating were recognised in male behaviour: (1) excitation with ASP and localisation of the female as an emitting source, (2) contacting the female, (3) mounting onto her dorsal surface, (4) crawling over the female opisthosoma to the ventral surface, (5) location of the female gonopore, stretching out the palps and inserting chelicerae and hypostome into the gonopore, (6) repeated copulatory movements, (7) lifting of male opisthosoma, shifting the genital opening above the female gonopore and ejaculation of the spermatophore, (8) fixation of the spermatophore in the female gonopore.