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308 condition, dark damp places dried, whitewashed, and ventilated. By these and similar measures much can be done to control the infection. Unfortunately, a mosquito-net having a mesh sufficiently small to keep out sand-flies is intolerable to a white man in a hot climate, and the influence of the essential oils is too evanescent to be of practical value.

Small hairy flies from 1.5-2.5 mm. in length, easily recognized by their form and thick hairy coat. The females only suck blood; in some people the bite causes a considerable local disturbance, in others little or none. The greater part of the body is covered with long yellow hairs, for the most part, probably, modified scales. The antennæ have sixteen joints. The proboscis is as long as the head and contains a number of piercing organs. The wings are definitely pointed, and on removal of the outer coating of scales the venation can be seen. The insect possesses six slender legs. The abdomen is divided into ten segments. In the female the abdomen is spindle-shaped, and is provided with an upper and a lower pair of small claspers. In the male there are five pairs of sexual appendages— the upper and lower claspers, and various other structures known as the " submedian lamellæ," "intermediate appendages," and "intromittent organ" (Newstead). The female lays her eggs in rubble walls and in caves. The eggs, six to nine days after being laid, hatch into twelve segmented caterpillar-like larvæ (Fig. 63), further characterized by two pairs of bristles on the posterior extremity and by the absence of eyes or organs of locomotion. In six to eight weeks the larvæ are 5 mm. in length, and feed on organic detritus and algæ. The pupæ are fixed in crevices of stones, slates, etc., the imagines emerging after fourteen days (Marett). In the classification of these insects, entomologists have relied on the slender differences afforded by the venation of the wings, the length of segments of the palps, the number and arrangement of the bristles or spines on the claspers. Up to the present there has been little agreement on this subject. A synoptical table of the genus follows; but it should be remembered that this classification must be regarded as temporary until the group has been more extensively studied. Great care must be exercised in the preservation of specimens for identification. The insects should be placed in a web-like layer of teased cotton-wool, but must not be covered with the wool, as even such slight pressure breaks their appendages.