Studies on the environmental factors for the breeding of grain mites : XII. Observations on the mode of breeding and of hypopus appearance of Lardoglyphus konoi (Sasa and Asanuma, 1951) in various kinds of diet

The studies were made on the mode of breeding and of hypopus formation of Lardoglyphus konoi (Sasa and Asanuma, 1951) in various kinds of diet. Two groups of diet prepared are as follows : Diet group A was based on the mixture of same weight of fish powder and yeast powder (control diet) with additional process. Some of them were added with 5% weight of soy bean oil. Diet group B was the mixture of yeast powder and one of the various kinds substances. Approximately 1,300 mites were inoculated on 20g of the diet and they were kept at 25℃ and 85% R.H. (regulated with KCl saturated solution). Number of mites in 0.5g of diet and number of mites escaped from the container were counted every week. The appearance rate of hypopus in the diet and in the escaped population were observed. The period of observations was separated into following 3 stages : 1st stage was from 1st to 3rd week, 2nd stage from 4th to 7th week, and 3rd stage from 8th to 10th week. Number of mites in Table 2 is the mean number per week in every stage. 1) The mode of breeding of L. konoi in A group diet. When soy bean oil was added in the diet at 5%, number of mites in these diets and of escaped mites rose up in the beginning of the experiment. Considering the nutritional contents of the diets may be classified in three types as follows : (1) fat abundant type; When the fat and other nutriments were contained enough in the diet, the mites counts were high even in the 1st stage and the peak of number of the mites was revealed in the 6th week and later population density of the mites decreased rapidly. This was the type that increasing speed of the mites population was high in initial period (for example, diet (1), (2), (4), (8) and (10)). (2) fat deficient type; when the fat was deficient but other nutriments were abundant in the diet, population density of the mites was low in the 1st stage. It ascended rapidly in the 2nd stage and was slowly down in the 3rd stage. This type was that the increasing speed of the mites population density was slow in the 1st stage (for example, diet (3) and (7)). (3) nutrient deficient type; when the nutriments were deficient in the diet, number of the mites was the highest in the 1st stage and decreased thereafter (for example, diet (5), (6), (11) and (12)). It was noticed that hypopus rates were higher in the nutrient deficient diets than in other diet of A group. In fish powder diet hypopus rate was the minimum in this study. 2) The mode of breeding and hypopus rate of L. konoi in the diet of B group. The maximum count of the mites was observed in the diet that whale meat extract was added to yeast powder at 5%. But in this diet, hypopus rate was low as well as in control. In the mixture of yeast powder and soy bean powder, milk casein, geratin or egg alubumin, population densities of the mites were lower than in yeast powder only. This fact may indicate that the various kinds of protein, added in yeast powder, were worse than yeast powder as a nutriment for the mites. The hypopus rate in these diets were higher than it in control diet or yeast powder. By the fact that increase of mite number was low in these diet, hypopus rate possibly increase due to deficiency of protein or unfit protein as a diet. Paticularly the mite density in soy bean powder was low, while the ratio of hypopus in that population was the highest.