The culex solicitans and stegomyia look very much alike to the naked eye, so much so that one of our most experienced inspectors at Panama, on returning from a vacation spent on Long Island, told me that the stegomyia was the common mosquito on Long Island. As a matter of fact, the stegomyia never appears farther north than Norfolk, Virginia, unless as a matter of accidental introduction during warm summer weather. As the inspector deals with the mosquito in the larval stage principally, he must be familiar with the habits of the larvæ, and the habits of the different larvæ differ about as much as the habits of the adult mosquitoes. They also differ much in size and shape; for instance, the larvæ of the anopheles can readily be recognized by the way it comes to the surface to breathe. During this process it lies horizontal to and in contact with the surface of the water. The culex larvæ, when breathing, lies with its tail up and head down. The anopheles is a long, very slender larva; the culex, short and chunky. The anopheles larva is most noticeable from its superior intelligence. It will dive and seek shelter in the grass at any sound or shadow thrown upon the water; the culex larva is sluggish and pays little attention to such things. [Illustration: Old French Engine Tender Used as Storage Tank for Oil] [Illustration: Mule for Packing Oil to Oilers.] The inspector must become very familiar with the half-dozen most frequently occurring larvæ in his district; he must recognize them easily when he sees them, and must know the kind of locality in which to seek for them. He must learn the peculiarity of ditching as applied to drainage intended to prevent mosquito breeding. This is quite an art in itself. Take, for instance, an ordinary depression between two small hills; if we want merely to get the water away for ordinary drainage purposes, a ditch through the center will accomplish this, but sometimes where the water is oozing through the surface on the hillside, you still have soft moist places on each side of your ditch which makes most excellent breeding-places for mosquitoes. Mr. Le Prince discovered that for mosquito work ditches would have to be run along the hillside to cut off the water from this soft ground and to catch it when it came to the surface. Where the ordinary engineer does ditching, such a detail as this is overlooked by him. Wherever possible, I insisted upon the sanitary inspector who was instructed in these matters doing his own work, using men employed directly by himself and under his orders and supervision. I think it is of the utmost importance in mosquito work that the health officer should have direct control of the men doing this work. The ordinary engineer has no special knowledge of the life history of the mosquito, and as the ditching and brush-cutting are done to prevent mosquito-breeding, it is not surprising that it is not successfully done by a man who has no knowledge of the mosquito.