Observations have been made on the distribution of adult and pupal keds over the body of sheep and lambs, and the seasonal changes in density and distribution have been followed by a series of counts on the same sixteen sheep throughout a period of 13 months.

The method of assessing the adult population by counting the living keds was checked by killing and subsequently counting them, and is believed to give approximately correct results. Pupal estimations by the ‘live-count’ method gave results apparently 50 % below the actual values.

The ked population builds up rapidly during late winter and early spring to a maximum in April and early May. A decline begins in May, and by June the population has decreased very considerably. During summer the unshorn lambs show a continued decrease, which may be due in whole or part to loss by transference to the shorn sheep.

The greatest concentration during the peak infestation is on the chest, lower shoulder and lower rib wool. In winter and spring the population is more generally distributed, and may show a preference for the upper over the lower side wool. In summer the back is practically deserted and the upper sides only sparsely populated. The throat and chest region is a favoured site the year round, and there is some indication that the throat may be a breeding area.

Generally speaking, the adult and pupal populations are proportionately distributed. In late spring, however, puparia tend to be laid to a greater extent, relative to the adult population, in the lower than the upper surface fleece.

The significance of the seasonal population shifts is discussed, and a method of eradicating keds from a flock by summer dipping of the lambs is outlined.