Although three other Ixodes species were found, Ixodes ricinus L., when it occurs, is by far the most important tick parasite of wild and domestic animals on hill and moorland grazings in northern England. In the following, ‘tick’ or ‘ticks’ refer to I. ricinus.

The previous list of British mammal hosts, wild and domestic, to the tick (any stage) is largely confirmed, and increased approximately from twenty-three to twenty-nine species; and birds, similarly, from twenty-one to thirty-nine species. The preponderance of small mammals and birds among the twenty-four new-recorded host species confirms the impression that previous workers tended to confine their attentions to the larger animals. The host list is still incomplete, and the suggestion that the tick will parasitize any bird or mammal it may meet is strongly reinforced.

No host occurs below the reptile level among vertebrates; and among British reptiles, only the common lizard is a host—rarely. There appear to be no hosts among invertebrates.

All the farm and domestic mammals from horse down to cat are hosts to female ticks, but poultry have never been recorded—probably because they do not much frequent the tick-infested pastures.

Only the larger wild mammals and birds are hosts to female ticks. In northern England these include eight mammals and three birds. For Britain as a whole two other mammals are known, while a further four mammals and one bird are likely hosts.

With or without the inclusion of domestic animals, proportionately more mammal than bird species are hosts to female ticks. This is because there are more mammal than bird species large enough to be hosts.

All the recorded British hosts, except shrew and possibly mole, are hosts in some degree to nymphs, and all, without exception, are hosts to larvae.

A certain amount of self-deticking is practised by birds, and very probably by some of the smaller mammals. Birds never have ticks attached within beak-reach.