IN a letter which appeared in your issue of September 29, Captain Traherne writes under the heading of “Horn-feeding Larvae,” of maggots of about half an inch in length and of a white colour, having been found in the horns of a newly killed sheep, which he had obtained in India, but where there were no perceptible signs of perforation. These were not the larvae of a Lepidopterous insect, but of one of the Diptera, known as AEstrus ovis, a well-known parasite. The fly lays her eggs in the region of the anterior nares, and the larvae penetrate the nasal passage, finding their way into the turbinal bones, and from thence into the frontal cavity to the base of the horns. Captain Traherne does not say how far up the horn he found them; they are not usually found beyond the base, but as a rule locate themselves at the back of the throat, where they feed on the mucous substance. They are not horn-feeders. AEstrus ovis is distributed pretty generally wherever sheep are to be found.