266 ENTOMOLOGY 



This disease of tropical and subtropical regions is caused by a thread- 

 worm, or nematode, known as Filaria bancroftij which occurs in the 

 blood of man and of several of the lower animals as a slender larva 

 (micro filar id) about one-quarter of a millimeter in length. At night 

 these larvae swarm in the peripheral circulation, from which they are 

 taken into the alimentary canal of a blood-sucking mosquito (chiefly 

 Culex quinquefasciatus) . In the mid-intestine of the mosquito the larvz 

 escapes from its sheath and penetrates into muscular tissue, where il 

 grows and develops for two or three weeks, after which it goes to som< 

 other part of the mosquito's body, often, to the base of the proboscis, 

 whence the larvae are carried into the blood of some vertebrate host, 

 there to develop to sexual maturity. 



The larvae are often common in human blood without seeming tc 

 injure the host in any way, but the adults (three or four inches long am 

 often found in groups) and ova that have escaped from the parent 

 female sometimes obstruct the lymphatic canals and cause enormous 

 swellings of feet, legs, arms or other parts of the human body; this 

 condition being known as elephantiasis. 



TYPHUS 



War and typhus have always gone hand in hand. Crowded an< 

 uncleanly conditions in camps and prisons are most favorable to the 

 propagation of the disease. 



Recent History.- The last scourge of typhus in Serbia began in 

 October, 1914 among Austrian prisoners, who spread the disease ovei 

 the country. No adequate means of checking the disease existed, and 

 in January, 1915 the epidemic was raging. In April there were 9,< 

 deaths per day; the total mortality for the first five months of 1915 

 being more than 100,000. This epidemic was checked largely by the 

 energetic efforts of Dr. R. P. Strong and his fellow- workers. 



Syria suffered from typhus in 1916, with more than 1,000 deaths 

 daily. In Roumania, 1916-1919, the mortality was 26,000. Mexico 

 City had 11,000 cases of typhus in December, 1915. In the Unit( 

 States the disease occurs now and then in a small way, but especially 

 among immigrants. 



Cause. The specific cause of typhus can not as yet be named wit] 

 certainty. It may be a certain spirochaete discovered in 1917- by 

 Futaki, who found it in the liver and urine of typhus victims, as well 

 in a monkey after inoculation with infected human blood. Others 

 have ascribed the disease to bacilli. 



