Injurious to Man. 25 



mite and also by inoculation. The causative organism is not yet 

 known with certainty. Larval forms closely resembling the one 

 which conveys the disease are parasitic on small mammals in 

 other uninfected districts in Japan, but their bite does not give rise 

 to any fever. It has been suggested by Ashburn and Craig that 

 this disease exists in the Philippines, and according to Dr. Schuffner 

 a very similar complaint occurs at Deli, Sumatra ; he gives photo- 

 graphs of a larval Trombidiid which may perhaps transmit the 

 disease, but it is possible that it is conveyed by a true tick 

 (Ixodidae). 



In France two or even three different larval forms belonging 

 to this group (Microtrombidium autumnale, Shaw ; Metathrom- 

 Helium ppriceps, Oudemans ; and perhaps also Trombidium 

 striaticeps, Oudemans) attack human beings during the hot and 

 dry montbs of "the year. So far, only one of these species, 

 Microtrombidium autumnale, Shaw, popularly known as the 

 " harvest bug," has been found in Great Britain. It fixes itself at 

 the base of a hair on the limbs or body, and its bite gives rise to 

 great irritation, which may last for days if not attended to, some- 

 times even causing insomnia. If a little ammonia is applied to 

 the wound it soon alleviates the pain, however. Gilbert White 

 gives the following graphic account of this Acarus in his " Natural 

 History of Selborne " : — " There is an insect with us, especially on 

 chalky districts, which is very troublesome and teasing all the 

 latter end of the summer, getting into people's skins, especially 

 those of women and children, and raising tumours which itch 

 intolerably. This animal (which we call an harvest bug) is very 

 minute, scarce discernible to the naked eye ; of a bright scarlet 

 colour, and of the genus of acarus. They are met with in gardens 

 on kidneybeans, or any legumens ; but prevail only in the hot 

 months of summer. Warreners, as some have assured me, are 

 much infested by them on chalky downs ; where these insects 

 swarm sometimes to so infinite a degree as to discolour their nets, 

 and to give them a reddish cast, while the men are so bitten as 

 to be thrown into fevers." 



In North America these larval Trombidiid mites are called 

 Jiggers or Eed Bugs (Leptus = Microtrombidium ? americanus, 

 Eiley, and L. irritans, Riley) ; Mr. Nathan Banks states that they 

 are a source of great annoyance in parts of the Southern States. 



Theobald recommends oil of citronnelle applied to the limbs 

 before walking as a preventive against harvest bugs. 



Another preventive is flowers of sulphur rubbed over the legs 



