Observations were made on male S. slriolalum at my pond at Swavesey, Cambridge, England, in the autum of 1989. The pond, which is 40 m long and 15 m wide, has a varied shore line. Male S. striolatum were found to perch in the warmer and more sheltered places round the edges of the pond. The distribution of these basking spots, and hence the distribution of the males, varied according to sun and wind direction. 1 marked some males individually and found that they perched in different parts of the pond’s circumference at different times. By providing an artificial basking spot in the form of a wooden basket, I could induce individual males to perch on it. By moving the basket very gently and slowly I was able to carry it, with the male still perched on it, to places by the shore up to 15 metres away into areas occupied by other males. Subsequent observations showed that the male which 1 had moved attacked intruders from its new position. This confirms the general observation that males "defend” the area round themselves rather than a particular locality. In autumn in England, when there is considerable variation in ambient and ground temperatures at different parts of the pond edge, it is probable that competition is primarily for basking places. These are then used as bases from which the male insects seek females and attrack intruders.