For indoor use insecticide methods are more suited; and the best of these are immensely more effective than some popular devices, which make a remarkable display and sell well, but which the purchasers soon become neglectful to keep in constant use. Traps in the form of wire-gauze cages, and glass non-return bottles belong to this latter class of contrivances; when seen crowded with struggling victims, the employment of such articles captivates many observers; but their real efficiency will be found to fall far short of general expectation. The explanation will be apparent when the use of the wire-cage trap is contrasted with the success of a good fly poison. Given, say, a dwelling room on a midsummer day containing ten female flies and ten idle dancing male flies; in such cases not more than half the females and one quarter of the males will get imprisoned within four or five hours by the employment of the wire-cage trap, but with a good method of setting poison nine-tenths of the females and half the males may be killed within the same period. In the case of poisoning, the dead have to be swept up, whilst fly traps have the advantage of collecting the victims; but, unless the inmates are carefully destroyed, a few will manage sometimes to escape from the traps, especially as side window light changes and daylight fades. In these fly traps it is only the perseverance of the prisoners in struggling towards outer light which prevents their exit by the entrance aperture. Stickfast adhesive papers and suspended tapes and strings look very effective when seen crowded with accumulated captures; but, again, these "exhibition" appearances are as deceptive in suggestions of real efficiency as are the crowded cage traps last mentioned; moreover, sticky messes are not commendable or convenient articles for placing where most wanted. Truly, suspensory strings are attractive resting resorts for dancing males, but the worst agents of Beelzebub are the females, which have a keener appetite for food and for pestering humanity. There remain for consideration insecticide poisons. A great choice of materials can be supplied by the chemist's shop, and various methods of using them have been recommended. In old times country people prepared decoctions of _Amanita muscaria_, the fly toadstool, a large orange-scarlet, or crimson, mushroom-shaped fungus commonly appearing in autumn in woods where birch trees abound. Strange to say, such decoction will poison flies of many kinds, although they, and many different creatures, feed with impunity on other fungi which are more deadly poisonous to mankind.