They are generally of a somewhat dingy appearance, the prevailing colours being dull shades of grey, drab, and brown. So closely, in fact, do certain of them resemble each other, that the greatest care has to be exercised in the identification of species--a task that is rendered still more difficult by the variations that we observe in the tints and markings of certain species. These moths have generally rather stout bodies. Their fore wings are somewhat narrow, and, when the insects are at rest, these are brought close to the body, and the hind pair are folded up beneath them. Family--BRYOPHILIDAE _The Marbled Beauty_ (_Bryophila Perla_) Our first family--the _Bryophilidae_--contains only four British species. These are small and slender-bodied moths, whose larvae feed in early morning on the lichens that cover stones and old walls, and conceal themselves by day in holes and chinks and under stones. The Marbled Beauty is the only moth of this family that may be described as common with us. It is abundant in nearly every English county, as well as in parts of Scotland and Ireland. [Illustration: FIG. 138.--THE MARBLED BEAUTY.] Its wings are very pale grey, marked with a darker bluish grey, as shown in the engraving. These markings are variable, but the bases of the fore wings have always a dark blotch, followed by a patch of pale grey or white, extending the whole width of the wing. The moth may be found from the beginning of July to the middle of September. The larva feeds from February to April. It is black above, with a broad orange-bordered stripe down the back; and its body is covered with small warts, each of which bears a single hair. Family--BOMBYCOIDAE In this family there are sixteen British moths, several of which are exceedingly common. They are much larger than the _Bryophilidae_, and of a much stouter build. The larvae are covered with little hair-bearing warts, and are, indeed, often so hairy that they may be mistaken for the caterpillars of the _Bombyces_. _The Grey Dagger_ (_Acronycta Psi_) This is the commonest of all the _Bombycoidae_. It may be found at rest on tree trunks and palings during the daytime throughout the summer. Its fore wings are pale grey, with four conspicuous black marks, one of which--that in the anal angle--resembles the Greek letter _psi_ ([psi]) placed sideways. [Illustration: FIG. 139.--THE GREY DAGGER.] The larva is black or very dark grey, with a pale yellow line down the back, and a black hump on each of the fifth and twelfth segments, that on the fifth being much larger than the other. It feeds in the autumn on lime (_Tilia vulgaris_), blackthorn (_Prunus spinosa_), whitethorn (_Crataegus oxyacantha_), fruit trees, and various other trees, shrubs, and herbs. The moth called the Dark Dagger (_Tridens_) is hardly to be distinguished from _Psi_. It is not really any darker, and its markings are almost exactly similar; but the larva is very different.