It is perhaps well known that the males of the genus Phlebotomus are purely “sexual forms,” i.e. their main function in life being to fertilise the females; they die after having copulated. In laboratory-bred strains of argentipes, it was found that the females were sought by freshly emerged males. I have observed that when a male approaches a female he sways his slender abdomen to and fro laterally and when close to her an unerring lateral swing of his abdomen links the two horizontally through the agency of the male terminalia. The couple remain in this horizontal position facing oppositely with the wings of the male placed ventrally to those of the female for about a minute, after which the insects separate. In several instances a couple in conjunction was seen to move or make short flights in a direction at right angles to their line of linkage.