58 ENTOMOLOGY FOR MEDICAL OFFICERS 



Dr Atkinson, of Hongkong, reports that the adults of 

 a water-haunting Dolichopodid fly (p. 141), and of an Antho- 

 myid fly of the wide-ranging genus Lispa (p. 180) devour 

 mosquito-larvse. And Dr Annandale, of the Indian Museum, 

 mentions the common fresh-water polyp Hydra as a chance 

 foe. Another mortal enemy is a fresh-water Amphipod 

 Crustacean (p. 322) of the genus Gammarus (Fig. 136). 



Floating plants of the duckweed order {LemnacecB) are 

 supposed, when they form a very thick growth, to crowd 

 out mosquito-larvae and prevent them coming to the surface 

 to breathe. Possibly some zealous reformer may some day 

 suggest that the Utricularice should be cultivated for the 

 purpose of catching mosquito-larvae. 



(b) Defence against Adult Mosquitoes. — It is generally 

 agreed that in swampy tracts, where it is impossible to make 

 much impression on larvae, the adults must be attacked. 



Ross, arguing for the prevention of malaria, very properly insists 

 that in all circumstances, even when active measures are taken against 

 larvse, the adults (and the prophylactic use of quinine) must not be 

 forgotten. 



Wind and sun are very bad for mosquitoes, so that 

 everything that is likely to give them shelter from either — 

 creepers, undergrowth, ruins, tumble-down outhouses, etc. — 

 should be cleared away from the immediate vicinity of 

 dwellings. 



Dark corners, cellars, sheds, etc., are very good for 

 mosquitoes. All such hiding-places should be looked to, and 

 if necessary, fumigated with sulphur, or sprayed with dilute 

 solution of formalin, or strong solution of crude carbolic acid, 

 or crude petroleum. 



Mosquito - proof houses and even mosquito - neits are 

 supposed to be a luxury for the white man, but in the island 

 of Minnikoy, where the population scrapes a precarious living 

 from the coco-nut, everybody — when I was there in 1891 — 

 used mosquito-nets. 



Mosquitoes can certainly be kept off by petroleum ; but a 

 lotion or emulsion of some aromatic oil (clove, anise, pepper- 

 mint, lavender, bergamot, turpentine, eucalyptus — or a taste- 

 ful combination of them) in strong spirit-and-water with a 

 little quassia or quinine is much pleasanter for personal use. 



