M 129
III. THE CATCHING AND DISSECTION OF MOSQUITOES.
46. In the dissections done throughout the year the following Anophelines were found infected—A. minimus, A. jeyporiensis, A. maculatus, A. hyrcanus, and A. tesselatus.
47. The infected A. hyrcanus and A. maculatus were obtained from the Shing Mun catches, the A. tesselatus from the Little Hong Kong catches.
Night catching in cattle sheds.
48. Hitherto A. maculatus adults have only been obtained in insignificant numbers in day or night catches done under ordinary circumstances in human habitations although large numbers of their larvae could be readily obtained in the neighbourhood.
49. It was decided to try catching in the Dairy Farm cattle byres but as they are well lighted and well ventilated buildings, there was little possibility of obtaining Anophelines in morning catches, therefore catching was tried for one and a half hours from dusk onwards.
50. A beginning was made at the end of April. The General Manager of the Dairy Farm when approached on the matter, gave all possible assistance. A cattle attendant who was provided with a catching bottle and electric torch, worked at first under the supervision of one of the Staff of the Bureau. Catches were done in the byres along Sassoon Road, and above Victoria Road north of Sassoon Road.
51. A. maculatus were caught feeding on the cattle, or resting on the walls of the byres, usually gorged with blood. On windy or rainy nights, few or none were captured, but on still nights catches of 50 were not unknown, sometimes the collection exceeded 100. During 164 nights, 2819 A. maculatus, 19 A. hyrcanus, 31 A. vagus, 6 A. minimus, 1 A. jeyporiensis were captured. Of the 6 A. minimus, 5 were caught in December.
52. The mosquitoes were brought to the Laboratory, blood taken from the midguts and sent to M. Toumanoff, Chef du Laboratoire d'Entomologie de l'Institut Pasteur de Saigon, who kindly had the samples examined for precipitin reactions. A report has been received that positive reactions for cattle blood have been obtained from 234 midguts of A. maculatus. A further report regarding the remainder is being awaited.
53. The salivary glands of 712 A. maculatus whose midguts had been used for precipitin tests, were examined for sporozoites, but none were found. No infections were found in the salivary glands or midguts of another batch of 597 A. maculatus.