The House Fly (_Musca domestica_, Fig. 62) is about three lines in length, ash coloured, with the face black, the sides of the head yellow, and the forehead yellow with black stripes; the thorax is marked with black lines; the abdomen is pale underneath, and a transparent yellow at the sides, in the males, and is speckled with black. The feet are black; the wings transparent, and yellowish at the base. This species is extremely plentiful throughout the whole of Europe. Every one knows how annoying it is towards the end of the summer, and especially so in the South of France during the hot season. The Ox Fly (_Musca bovina_), a near relation of the house fly, is also very common. It settles on the nostrils, the eyes, and the wounds of animals. The Executioner Fly (_Musca carnifex_), which is not rare in France, also attacks oxen. It is of a dark metallic green colour with a slight ash-coloured down. Its forehead is silvery at the front and sides; the abdomen is edged with black; the wings hyaline, and yellow at the base. _Section of the Anthomyides._--The section of _Anthomyides_ comprises insects which appear to be _Creophili_ whose organisation has become weakened by almost insensible degrees. Their colours vary very much--black, grey, and iron-colour are everlastingly shaded and blended together. To that may be added reflections which are above the ground colour, and which change the hues of the little animal according to the incidence of the rays of light. The _Anthomyides_ resemble the genus _Musca_ very closely in their habits as well as in their organisation. In this group of Diptera we will first say a few words about the _Anthomiæ_. These flies are to be found in most gardens, and on all flowers, particularly on the heads of Compositæ and Umbelliferæ. They often unite in numerous bands in the air, and indulge in the joyous dances to which love invites them. The females deposit their eggs in the ground, and their larvæ are there quickly developed. The latter suspend themselves to certain bodies, the same as some lepidopterous chrysalides, in order to transform themselves into pupæ. The _Anthomyia pluvialis_ (Fig. 63) is from two to four lines in length, and of a whitish ash-colour. Its wings are hyaline, the thorax has five black spots, and the abdomen three rows of similar spots. [Illustration: Fig. 63.--Anthomyia pluvialis.] We will stop a moment with the _Pegomyiæ_, which are very interesting in the larva state, and which excited the interest and sagacity of Réaumur.