The Common Blue, as well as the Chalk Hill and the Adonis Blues, are to be found, often commonly and sometimes in large numbers, in their favourite haunts. Each of them is subject to a considerable range of variation on the under side, and this seems to be of a similar character in all. Very striking aberrations are, perhaps, not often obtained, but still many modifications are to be found, and the possibility of a really good thing turning up, induces one to give attention to the business of overhauling these butterflies. A very good method of conducting this kind of work is to first ascertain the places where they chiefly congregate, and then to visit there on dull days or late in the afternoon, when the butterflies are asleep or, at all events, resting. They can then be easily examined as they sit on the long grass stems, etc. (Plate 27), but only the under sides can be viewed in this way. So to avoid passing over a good upper-side variety, it will be needful to take each specimen between the finger and thumb of the right hand, seizing the closed wings gently, but firmly, near their base, and then quickly secure the thorax from underneath with thumb and index finger of the left hand, when the upper as well as the under side becomes available for inspection. There is no reason whatever to damage the insects in any way, and those that are not required may be set free again none the worse for their short detention. Work against the wind, and to avoid a second interview, turn rejected specimens to the rear. [Illustration: _Pl._ 108. =Chalkhill Blue.= _Egg enlarged; caterpillar and chrysalis._] [Illustration: _Pl._ 109. =Chalkhill Blue.= 1, 2, 8, 10 _male_; 3, 4, 5, 6, 7, 9, 11, 12 _female_.] The Chalk Hill Blue (_Lycæna corydon_).