Chrysops is a genus of Tabanid fly. The Florida species is the deer fly or Chrysops discalis, which may be one of the transmitters of tularemia. This fly is probably familiar to those especially who do any hunting or fishing, as in the spring of the year they certainly can bite. REPORT OF CASE In 1938 L. D., a white man aged 45, came into my office complaining that the deer fly bites he was receiving while working in his grove were getting to a point where they were disabling him. He had never been particularly bothered by them until that spring, although he had been in Florida in the grove business since 1926. However, now when he received a bite, which was mostly on his wrists, as he had begun to protect his face and neck with mosquito netting and his hands with gloves, his arm would swell and become painful. The flies, which in previous years had not bothered him, now seemed to be attracted to him and preferred him to any other person working in the grove. They had become so bothersome that it was hard to work in the grove on their account, even though he had protected himself with screening.His physical examination was negative and he had no history of any allergy. I gave him some ephedrine sulfate and suggested that he use oil of citronella or some other insect repellent. A few days later he came back to the office and his right hand, forearm and arm were swollen to what seemed to me to be twice the normal size. The wrist had areas of erythema, and red streaks radiated upward on the forearm, which was very painful. This was about 11 a. m. and he gave a history of having been bitten by a deer fly the previous morning about 10 o'clock and his hand had begun to swell, continued to swell and became quite painful until the swelling had reached his shoulder by the following morning, when he became alarmed and came to the office. His physical examination again was negative, except for his right upper extremity. I prescribed a wet magnesium sulfate dressing, epinephrine hypodermically and continuation of the ephedrine sulfate, and I advised him to stay indoors. I also asked him to get me some deer flies to make an antigen. He brought me 35 deer flies the next day. His arm was somewhat better, but I told him to continue the wet dressings and to return the following day.I had not had any previous experience in making insect antigens. I macerated 30 of the flies in 30 cc. of a buffered solution, making a strength of 1 deer fly to 1 cc. of the buffered solution, and put it through a Seitz filter. The solution was clear and colorless after filtering and was cultured on plain agar and Loeffler's medium and in bouillon for one week. No organisms were found, so 0.1 cc. of antigen was injected intracutaneously in my arm. There was no reaction, so in twenty-four hours 0.1 cc. was injected into the arm of my technician, with no reaction. In the meantime the patient's arm had become normal and he was given 0.1 cc. intracutaneously of the antigen. The injection caused a red wheal about 1 cm. in diameter, which had practically...
