Although the majority of the _Sylviidæ_ are fruit-eaters, the species now under consideration are almost entirely insectivorous;[7] they are also more strictly arboreal in their habits, and as regards the character of their nests, they differ remarkably from other members of the _Sylviidæ_ in building domed nests on or near the ground, instead of cup-shaped nests at a distance from it. The Yellow-billed Chiff-chaff—or Icterine Warbler, as it should now be called[8]—however, forms an exception to the rule, as will be seen later. As these little birds make their appearance at a season when caterpillars and destructive larvæ begin to be troublesome, the good they do in ridding the young leaves and buds of these pests is incalculable. I have watched a Willow Wren picking the green _aphis_ off a standard rose-tree, and have been as much astonished at the quantity which it consumed as at the rapidity of the consumption. The Wood Warbler is not nearly so sociable as either the Willow Warbler or the Chiff-chaff. It keeps to the tops of trees in woods and plantations, and seldom comes into gardens; hence it is not so often seen. Although not rare, it is somewhat local, and in the British Islands, it appears, is confined exclusively to England and the south of Scotland. Mr. Thompson has included it with hesitation amongst the birds of Ireland; for although the description given to him of certain birds and eggs seemed to apply to this species, it was stated that the nest which contained the eggs was lined with feathers. Now, the Willow Wren invariably makes use of feathers for this purpose, but the Wood Warbler does not. The nest of the latter is composed entirely of dry grass and leaves, occasionally mixed with a little moss; and although I have sometimes found horsehair inside, I do not remember to have seen or heard of an instance in which any feathers were employed. The eggs, five or six in number, are white, closely freckled over with reddish brown.