At first you will find the leno rather stiff and harsh, but a damping and good rubbing between the hands will soften it down; or, if you prefer it, you may soften the material by a slight washing before cutting out the net. The latter is perhaps the better plan, for the washing will remove the objectionable 'dressing' that renders the material rather hard and stiff. Of the three colours mentioned above, green is the one most generally chosen, because it is more in harmony with the surroundings of a butterfly catcher; but many prefer the white leno to the green, as the insects are more easily seen in a net of this colour. Yellow is certainly not a desirable tint. As a rule it will be necessary to kill an insect as soon as it is captured. This is always the case with butterflies unless you require to keep them alive either to watch their movements or to obtain eggs. For this purpose you will require a killing bottle or box containing some volatile substance. The selection of this necessary piece of apparatus is a point deserving of much consideration, for so many different forms are in use by different entomologists, and so many advocates each declare that his own plan is far superior to that of any of the others, that the final decision is not to be worked out in a moment. The best thing for a beginner is to try as many as he can, and then, after some considerable experience of his own, he will be able to decide which apparatus suits himself best. I recommend this because it is impossible to say of any one plan that it is the best, for that which gives perfect satisfaction to one individual will often fail to give anything but annoyance in the hands of another. To enable my young readers to follow the advice I have just given, I will describe some of the commonly used killing arrangements and show how they should be used. I will take first the 'cyanide bottle.' This is a wide-mouthed bottle, containing a very poisonous substance called _cyanide of potassium_. It is fitted with a good sound cork. The 'cyanide' is a solid substance, and must be fixed in some way or other at the bottom of the bottle so that it cannot shake about and damage the butterflies. [Illustration: FIG. 43.--THE CYANIDE BOTTLE.]