Surcouf has noted that these fly larvae have been found cemented to mosquitoes of the genus Janthinosoma by a glue-like substance. These mosquitoes are vicious biters and evidently the young larvae escape from the eggs attached to the mosquito and enter the wound made by the biting parts of the mosquito. Some have thought that D. cyaniventris deposits its eggs in a glue-like material on the leaves of plants and that they stick to mosquitoes flying about such plants. From the facts that these eggs apparently only become attached to this particular mosquito, and further in that the eggs are attached in a constant manner with the hatching end outward, it would seem that the mother fly must in some way seize the mosquito and deposit her eggs on it. As the larva grows in the subcutaneous tissues of man or other animals a tumor-like swelling develops with a central orifice, toward which the posterior extremity of the larva points and through which it takes air into its spiracles.
It has been stated that the eggs of D. cyaniventris may be conveyed by ticks.
The swelling somewhat resembles a blind boil and may be as large as a pigeon’s egg.
These botfly boils tend to break down and discharge a sero-purulent fluid and it is supposed that the larva, when mature, escapes as a result of the disintegration of the tumor.
In Brazil they make tobacco juice applications which cause the larva to protrude and then squeeze it out. The injection of a little chloroform into the larva with a hypodermic syringe, prior to its extraction with a forceps, makes the process less painful.
The Screw Worm.—This is the larva of a bluebottle fly, Chrysomyia macellaria, which differs from the common bluebottle fly, Lucilia, by having 3 black lines on scutum. This muscid fly lays 200 to 300 eggs in wounds or orifices having offensive discharges, as from nose, ears, etc. The larvae burrow into the adjacent tissues and cause frightful destruction of all soft parts. The mature larvae are a little more than ⅔ inch long and have circlets of spines around each of the 12 segments.
This infection is especially common in tropical and subtropical America and is important in animals as well as man.
In Yount’s 23 cases 18 were of nasal myiasis; the mortality for the 23 cases was 15% and for the nasal ones 22%. Irrigation with chloroform water or a 5% carbolic acid or compound cresol solution gives the best results in treatment. If the larvae reach the sinuses it may be necessary to open them to get at the parasites.
Creeping Eruption
This is a skin affection which is also called larva migrans on account of its being due to the burrowing of more or less undetermined fly larvae in the subcutaneous tissues. In their advance, which is at the rate of from one to several inches daily, they leave a raised pinkish line. The burrow is approximately ⅙ inch in diameter. The disease is most common in Southern Russia but is also found in Africa, Asia and South America. Looss considers that hookworm larvae, when penetrating the skin, may produce similar lesions.