_Polietes lardaria_ is a fly sometimes mistaken for the blue-bottle; its specific name is rather too suggestive of resemblance in habit. It may be recognised by its having four black stripes on the thorax, by its large white squamæ, and its tesselated glaucous abdomen; its wing pattern classifies it as belonging to the _Anthomyidæ_, whilst the true blue-bottles belong to the _Muscidæ_, and the grey blow-flies to a section (_Sarcophagina_) of the _Tachinidæ_. There are some other outdoor flies which are not very dissimilar to the common blue-bottle, but they are more soberly coloured, ranging from bluish black to speckled and tinted greys; some of these have a pattern on the shiny upper surface of the abdomen which is conspicuously and beautifully chequered. Closely akin to these latter is the large grey blow-fly, or flesh-fly, _Sarcophaga carnaria_; it is much referred to in entomological books as of marvellous fecundity. The female deposits not eggs in a few hundreds, but already hatched maggots to the number of many thousands. Amongst half-a-dozen rarer kinds of smaller grey blow-flies the females differ in their striped markings, but their respective males seem quite indistinguishable apart. Notwithstanding the prodigious fecundity of the grey blow-fly, the credit of being a practically useful scavenger of carrion must be given only to the blue-bottle, which is of a more robust habit, and which so promptly monopolises available matter that _Sarcophaga carnaria_ and her congeners are sometimes, perforce, compelled to give their larvæ a mere vegetarian diet. The yellow cow-dung fly, _Scatophaga stercoraria_, is inoffensive, and one of the commonest flies observable in the course of a country-side ramble. It and its congeners are distinct in habits and appearance from any of the other flies above-mentioned. In this species the male is larger than the rather more smooth and dull-coloured female. Its body is furry but slender; it has small eyes and head parts. In repose it holds its wings parallel close above the abdomen, more like the "breeze-flies," or true "gad-flies," than the ordinary muscid flies. Although its proboscis does not seem as formidable as that of more insectivorous flies, yet it may sometimes be observed pouncing upon some small fly, which it holds with its powerful legs. This fly does not appear to be very predaceously inclined; perhaps it is only "acting a part," like some other creatures, including the amorous male of the common frog, which, failing to secure a more natural and complacent "partner in the dance," will in springtime seize upon and very persistently cling to an astonished carp.