抄録
Clinical observations were made on the bite of horsefly larvae which was seen on hands and feet of farmers working in the paddy-fields mainly in the period from the time of rice-planting to weeding, usually from May to July and biology of the larvae was also studied. Their bites were almost found at the exposed extremities sticking in the mud. The results obtained are summarized as follows : 1) In all of twenty cases observed in the paddyfield there occurred momentary sharp pain left with small puncture wound at the site of bite, being accompanied with raised hyperemic swelling which was intensely itching. Some of them had to be given medical treatment. 2) Predisposing sites of the lesion were ankle region, fingers, legs and dorsum of the hand, in that order. 3) Hypoesthesia was revealed in the area distal to the wound corresponding to a certain nerve supply in six cases in which sites of bite were lateral surface of fingers or ankle region. 4) Experimental bites using the larvae carried out in six volunteers led the same symptoms produced by natural bites. 5) The poison-pouring mechanism by the bite of the larvae was believed as follow. Puncturing of the skin by mandibles with sawtoothed margins, function as a pair of scissors in snipping the skin, produces a wound through which the saliva is introduced. 6) Differential diagnosis of this entity from other dermatitis caused by the work in paddy-field is easy in typical cases in which sharp pain at the moment of bite followed by the irritating local pruritus is characteristic. 7) Eight species of Tabanidae (six of Tabanus and two of Chrysops) were obtained by individually rearing of the horsefly larvae collected in paddyfields where the bite occured frequently. 8) The larvae were more numerous in the mud of "Nawashiro" (beds for rice-plants) than "Honden" (common paddy-fields) and many moulting pelts of pupae were found in ridges between fields. 9) It was very interesting that many overwintering larvae were left exposed on the mud of paddy-fields just after snow-break in spring.
