cc. Palpi nearly as long as the proboscis. Smaller species than the house-fly. The horn-fly (fig. 167) _Hæmatobia irritans_ bb. Mouth-parts blunt, fitted for lapping. c. Thorax, particularly on the sides and near the base of the wings with soft golden yellow hairs among the bristles. This fly is often found in the house in very early spring or even in the winter. The cluster-fly, _Pollenia rudis_ cc. Thorax without golden yellow hairs among the bristles. d. The last segment of the vein M with an abrupt angle. (fig. 108). The larvæ live in manure, etc. House-fly, _Musca domestica_ dd. The last segment of vein M with a broad, gentle curve (fig. 102). e. Eyes microscopically hairy; each abdominal segment with two spots. Larvæ in dung. _Myiospila meditabunda_ ee. Eyes bare; abdomen gray and brown marbled. _Muscina_ f. With black legs and palpi. _M. assimilis_ ff. With legs more or less yellowish; palpi yellow. Larvæ in decaying vegetable substances, dung, etc. _M. stabulans_ It is almost universally believed that the adults of _Musca domestica_ hibernate, remaining dormant throughout the winter in attics, around chimneys, and in sheltered but cold situations. This belief has been challenged by Skinner (1913), who maintains that all the adult flies die off during the fall and early winter and that the species is carried over in the pupal stage, and in no other way. The cluster-fly, _Pollenia rudis_, undoubtedly does hibernate in attics and similar situations and is often mistaken for the house-fly. In so far as concerns _Musca domestica_, the important question as to hibernation in the adult stage is an open one. Many observations by one of the writers (Johannsen) tend to confirm Dr. Skinner's conclusion, in so far as it applies to conditions in the latitude of New York State. Opposed, is the fact that various experimenters, notably Hewitt (1910) and Jepson (1909) wholly failed to carry pupæ through the winter. [Illustration: 108. The house or typhoid fly (Musca domestica (×4)). After Howard.] The house-fly breeds by preference in horse manure. Indeed, Dr. Howard, whose extensive studies of the species especially qualify him for expressing an opinion on the subject, has estimated that under ordinary city and town conditions, more than ninety per cent of the flies present in houses have come from horse stables or their vicinity. They are not limited to such localities, by any means, for it has been found that they would develop in almost any fermenting organic substance. Thus, they have been bred from pig, chicken, and cow manure, dirty waste paper, decaying vegetation, decaying meat, slaughter-house refuse, sawdust-sweepings, and many other sources. A fact which makes them especially dangerous as disease-carriers is that they breed readily in human excrement.