150 ENTOMOLOGY FOR MEDICAL OFFICERS 



acid, and, for the fearful stench, a solution of permanganate 

 of potash. 



It has to be remembered that house-flies and blow-flies, 

 which the civilised man — who does not and cannot live 

 according to nature and the recommendations of Stoic 

 philosophy— has now learned to regard as dangerous, are, 

 from the natural point of view, by no means altogether a 

 curse. Their maggots are unceasing scavengers, consuming 

 a vast amount of unconsidered filth, and if they are kept 

 in their proper place, quite remote from dwelling-houses, 

 may do good service in parts of the world where sanitation 

 is of a primitive kind. 



In the Muscidae which we are now considering the arista 

 is feathered both dorsally and ventrally ; the 4th longitudinal 

 vein is bent abruptly forwards at an angle, so as nearly to 

 close the ist posterior cell; and the proboscis (Fig. 10) is 

 broad, for the most part soft and retractile, and ends in 

 large fleshy expansile labella. In each labellum there is 

 a radiating arrangement of numerous tubules which in 

 structure and appearance resemble tracheae : these, which 

 are known as pseudotrachecB (Fig. 3), open on the under 

 surface of the labellum and are used for absorbing nutri- 

 ment, their bases being furnished with Y-shaped teeth for 

 abrading the food. The other features of the proboscis 

 are represented in Fig. 3. 



There are numerous genera of Muscidae which are 

 domestic pests ; the commoner genera, which the medical 

 officer should be able to recognise, may be tabulated as 

 follows : — 



Table of Important Genera o/MuscidEe. A. 



Hypopleura without any tuft or comb of bristles ; tibias of middle 

 legs without any bristle near middle of inner surface Musca. 

 Hypopleura with a vertical row of bristles ; tibiae of middle legs 

 with a large bristle or bristles near middle of inner surface 



= 2 

 'Thorax and abdomen bluish-black, not lustrous ; cheeks hairy 



Calliphora. 



Thorax and abdomen green, or bluish-green, or bronze-green, and 



of a brilliant metallic lustre ; cheeks not thickly hairy = 3. 



Thorax and abdomen dirty brownish-yellow, cheeks very sparsely 



pubescent _ r 



