The earliest of the butterflies make their appearance on the wing in April, or, if the weather is mild, towards the end of March; and from this time you can find employment up to the end of September or the beginning of October--a period of about seven months. But it must not be supposed that all parts of this long season are equally prolific, and will yield equally valuable catches. Remember the short term of a butterfly's life, and bear in mind that each one has its own regular season in which to spend the winged state; you will then see that anyone who wishes to 'work' as many species as possible must arrange his outings in accordance with the insects' own times. Some butterflies are double-brooded, and the two broods may not come forth at certain fixed times. Hence they seem to be on the wing almost without cessation for several months together, and therefore need not have a special day set apart for them. But others are more uniform in their date of appearance, and die off at about the same time. To catch such as these you must be careful to watch the weather, make allowance for any severities that may tend to cause a delay, or an unusually high temperature that may hasten their emergence, and then select a day in which you may expect to find them fresh and unworn. A week too early, and none are to be seen; a week too late, and nearly all you catch are worn and worthless. A glance at our Calendar (Appendix II) will give you a few illustrations in point. Thus you will observe that May is a month for the 'Whites,' early 'Blues' and certain of the Fritillaries; July for most of the Hairstreaks and Browns, and so on. Before you have been long collecting you will have captured the very common species, and then you will find that your butterfly hunts are very unproductive unless you make it a point to try for certain species at the proper times. Time, however, is not the only thing to take into account when preparing for a day with the butterflies. It is equally important that we should carefully select our locality in accordance with the known haunts of the various species. As long as you are simply working up the common kinds, you may wander almost at random in waste places, flowery meadows, corn fields, railway banks, &c.; but when you have secured a few specimens of each of these, you must search out the favoured resorts of the more local and the rarer species. For instance, wooded spots must be visited if you are to take certain of the Fritillaries, oak woods for the Purple Emperor and the Purple Hairstreak, fenny districts for the beautiful Swallow-tail, and so forth. In some cases the butterflies are closely restricted to certain isolated localities, to which you must travel if determined to obtain them.