Huckettomyia watanabei n. gen. and n. sp. is described from material of both sexes from the Japanese islands of Hokkaido and Honshu. A specimen from the Krasnoyarskiy district of Central Siberia is provisionally assigned to this species. The genus belongings to the tribe Hydrotaeini of the subfamily Muscinae, and differs from the other genera of the tribe by the setulose prosternum.

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Segregation of the siphonal hair types was observed in the progenies which were produced from the parent populations composed of type 5-4 larvae of the siphonal hair type in Culex pipiens molestus (Tables 3 and 4). When the selection continued ; the frequency of type 4-4 decreased, but not falling down to 30% ; that of type 5-4 changed in the opposite direction to that of type 4-4 ; that of type 5-5 fluctuated between 4.5 and 25.4% ; and those of types 4-3 and 3-3 rarely occurred. Viability of the type 5-4 populations did not show an apparent decrease, even though the selection was repeated under the experimental conditions.

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The mesostigmatid mites as predators of muscid flies were collected during 1967 to 1969 from experimentally deposited live-stock dungs in Chiba. At least 8 species of mites belonging to 3 genera of the family Macrochelidae were identified in the samples. In addition, some parasitid and uropodid mites were abundant.

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Mosquitoes were collected by light traps equipped with a 6 watt black-light-blue fluorescent lamp, in the National Institute of Animal Industry, Chiba, in the summers of 1967 and 1968. The females of Culex tritaeniorhynchus collected were dissected to determine the physiological age composition. Most of the females collected throughout a night had the follicles of N〜I.II stages, i.e., just before or after feeding. However, the parous rate of the population was higher in the later part of the night ; especially females just after oviposition, which are indicated by sac-like ovarioles, were more abundantly collected in the later part of the night. Also, the physiological age composition of females varied with the environmental conditions at collection sites. The females collected at the place near to the breeding site were observed to have the follicles of various stages at No, N〜I.II, II, III or V, but the follicles in most of the females collected near the pigsties were at N〜I.II stages.

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This study was made to observe the mode of breeding and hypopus formation in Lardoglyphus konoi (Sasa et Asanuma 1951) under the different temperature and relative humidity. About 300 mites were bred in diet which consisted of 4 parts of dried yeast and 6 parts of fish meal powder (niboshi), under the following experimental conditions. A series of relative humidity was prepared using 5 kinds of saturated salt, K_2SO_4(98%), KNO_3(94%), KCl(87%), NaCl(76%) and NH_4NO_3(66%). Each of series was set at 20℃, 25℃, 30℃ and 35℃. In each series of temperature, the highest count of mites were observed under 87% R.H. The Optimum temperature for the breeding of mites was 30℃. The time to reach the highest count of mites was shortest at the 35℃. The counts of escaped mites from diet had a tendency to increase with the total number of the mites in diet. Mites escaped most actively from the diet under the condition at 35℃ and 76% R.H. Hypopi less appeared under unfavorable condition for breeding. The hypopi in the diet appeared most in 94% and 66% R.H. at 30℃ (optimum temperature for breeding), whereas those in the escaping colony were most abundant in 87% R.H. at the same temperature.

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Feeding preference and lethal dosage of Norway rats on warfarin baits were studied in laboratory. The accumulated lethal dosage with 5 day successive feeding of warfarin baits were 3.13-8.00mg/kg and the lethal dosage with one day feeding was 264mg/kg. The feeding preference on 0.03% and 0.1% warfarin baits was equal to non-poisonous bait. This means that their avoidance of warfarin dry baits is not shown, if the concentration is as low as 0.1% or 0.03%. Days necessary to kill the rats by successive feeding of warfarin baits were 3 to 8 days from the initial feeding, independent of the total dose consumed, if the concentration is in the range of 0.03% to 0.1%.

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During the period from July 1968 to August 1970, some species of trombiculid mites, microtigroup and Acomatacarus yosanoi, were collected from the Northern part of Honshu, Japan, which have been considered to be uncommon species in this area. The places of collection recorded are as follows : Neotrombicula pomeranzevi Schluger, 1948 : Fuketsu, Hanaya-cho, Akita Pref. ; Mt. Hakkoda, Aomori Pref. ; Yakeyama, Towada City, Aomori Pref. ; Zato-ishi, Hirosaki City, Aomori Pref. N. microti Ewing, 1928 : Mt. Iwaki and Mt. Hakkoda, Aomori Pref. A. yosanoi Fukuzumi et Obata, 1953 : Mt. Taihei, Akita Pref. In view of the investigations recorded above it can be suggested that the distribution of these species of trombiculid mites are more extensively in Japan.

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[in Japanese]

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