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Since Baker and Wharton (1952) regarded the genus Mealia Trouessart, 1897, as a synonym of the genus Dermatophagoides Bogdanoff, 1864, many authors (Sasa, Dubinin, Baker et al., Hughes, Fain and others) have adopted the genus Dermatophagoides for the free-living mites which abound in the house-dust and other sources. When Fain (1966) redescribed Dermatophagoides pteronyssinus (Trt.) which was a dominant species in the house-dust, he suggested that it was impossible to define with certainty that D. pteronyssinus (Trt.) is not a synonym of D. schermetewskyi Bogdanoff, 1864. He did not, however, regard the former as a synonym of the latter, and stated that "Nous proposons donc de maintenir les deux especes et d'attendre que la decourverts de nouveau materiel puisse nous fixer sur le statut de D. scheremetewskyi". When he completed a monograph (1967a) on the genus Dermatophagoides, he could not include the redescription of the type species of the genus, i. e., D. scheremetewskyi. This means that the genus Dermatophagoides was reestablished without defining type species. That the dominant form found in the housedust is identical with Trouessart's Mealia pteronyssina seems highly probable on the following grounds : 1) Dr. Fain ascertained that his materials (D. pteronyssinus) was identical with the type series of M. pteronyssinus which was actually preserved in Berlese Collection of Florence with data written by Trouessart (1901) "Habitat : Sur des peaux de Mammiferes preparees et attaquees par des Insectes rongeurs (par M. Petit aine, de Paris", 2) we ascertained the identity between our materials from the house-dust and D. ptronyssinus sensu Fain, and found that our material falls within the category of the genus Mealia Trt., and specifically coincide with M. pteronyssina Trt. according to the original description. In Bogdanoff's original description of D. scheremetewskyi, we found that D. scheremetewskyi is definitely distinguishable morphologically from the species of the genus Mealia Trt. In the female of Bogdanoff's D. scheremetewskyi, 1) palpal tarsus is rather slender and pointed forwards, 2) a pair of external vertical setae are present and are provided with some ten pectinations, 3) a pair of pores which may be traces of internal vertical setae (which must have fallen off) are present, but are drawn by mistake between epimera I and II of ventral view (1B), 4) the propodosmal shield is lacking but that part is carefully and finely striated, 5) both posterior ends of epigynium (lesextremites de l'arc superieur) turned slightly outwards and reached the same level of the scapula of trochanter III, 6) the posterior ends of lateral vulva (les extremites posterieures de ce second arc) reached the same level of the scapula of trochanter IV. In the female of Mealia pteronyssina Trt., 1) palpal tarsus is rather short and turned strongly inwards, 2) both external and internal vertical setae absent, 3) a distinct propodosomal shield is present, 4) the epigynium is likely crescent or house-shoe shaped and the posterior ends do not reach the level of the scapula of trochanter III but may or may not reach the level of the anterior ends of epimera III, 5) the posterior ends of lateral vulva exceed beyond the level of the scapula of trochanter IV. Thus, it is clear that Bogdanoff's genus Dermatophagoides differs from the genus Mealia Trt. We propose, therefore, that the genus Mealia Trt. should be revived for the forms of free-living mites in the house-dust instead of the genus Dermatophagoides, which should be maintained for the true exoparasitic forms as like as the original habitat. It was also emphasized in the present paper that the male mite (described in the Bogdanoff's paper at the same time with the female of D. scheremetewskyi) is not concerned in the problem of the identity of D. scheremetewskyi Bogd., because he only sta

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Two myobiid mite species, Protomyobia brevisetosa Jameson, 1948 (known from U. S. A.) and Amorphacarus elongatus (Poppe, 1896) (known from Europe), were reported from shrews (Sorexunguiculatus, Sorex caecutiens saevus) of Hokkaido, Japan. Both of these mites showed minor host specificity and are often found together on a same shrew. Hokkaido specimens of A. elongatus differ slightly from the descriptions of A. elongatus by Poppe (1896) and by Radford (1948), but more specimens are needed before we can confirm the difierences between Hokkaido population of A. elongatus and those of Europe.

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The difference of larval period between the male and the female was observed on Culex pipiens pallens. In both sexes, period of 2nd instar larva was the shortest, 1st, 3rd instar larval and pupal stage came next and 4th instar was the longest. No differences were observed between the male and the female in the length of periods of the 1st, 2nd, 3rd instar larval and the pupal stages, but that of the 4th instar of females was longer than that of males. Generally speaking, the male emerges 1-2 days earlier than the female, and this phenomenon seemed to depend on mainly the difference in the length of 4th instar larva.

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Following the studies reported in the previous paper on the relationship between hypopus production and the environmental factors in grain mites, a series of experiments were carried out to observe the reproductivity and the stage composition of a a population of Lardoglyphus konoi (Sasa et Asanuma, 1951) when exposed to conditions of different relative humidities. The material used in the present experiment was a colony of L. konoi in a diet composed of a mixture of dried yeast and fishmeal powder at the ratio of 4 : 6, for 4 weeks at the temperature of 25℃ and the relative humidity of 75%. The material contained an average mite count of 256 per 0.5g at start of the experiment. Each 10g of the mite containing diet was divided into small glass vials and were placed in glass dessicators containing saturated solutions in water of various salts giving different relative humidities, such as 98% with K_2SO_4, 94% with KNO_3, 87% with KCl, 82% with Na_2SO_4, 76% with NaCl, 66% with NaNO_2, and 51% with NaHSO_4・H_2O. All the containers were kept at 25℃. 1. The population density and the stage composition of mites in the diet. The trend of increase in the density of mites were seen at relative humidities above 75%, with the maximum of 912 per 0.5g at 82% after 7 days, while the population density was found to decrease gradually at lower humidities of 66% and 52% from as early as 2 days after the exposure. As for the stage composition of the populations, reduction in the ratios of adults as well as increases in those of protonymphs was seen from after 2 days at lower humidities, while the composition remained almost unchanged for about 2 weeks at the higher humidity conditions and the ratio of adults began to increase from after 17 days. The appearance of the hypopus was observed from about 10 days at all humidities, and its highest ratio was seen at the optimum reproductive condition of 82%, forming a peak in the range from 87% to 76%. 2. The numbers and the stage composition of the escaped mites. The containers of the mites were placed each on petri dish containing saturated solutions of the respective salts, and the numbers as well as the stage composition of mites escaped from the diet and water surface were examined everyday. Large numbers of the mites were found to escape from the containers at lower humidities seen after start of the experiment, while the beginning of such migration was delayed for one to two days in containers exposed to humidities higher than 94%. In all the cases, the peak of the numbers of escaped mites was seen during the period when the population density of the mites in the diet began to decrease. The ratios of the numbers of escaped mites to the density in the original diet were the lowest in the optimum reproductive conditions of 82%, 94% and 98%, and the highest at the lowest relative humidity conditions. In the initial stage of the mite culture, most of the escaped mites were the adults, but mites of younger stages were found also to migrate in later stages, and the ratios of the latter stages gradually increased along with the increase in the population density in the original diet. The appearance of the hypopus among the escaped mites was seen from about the 8th day in most cultures, but was delayed for a few days at the highest humidities. It was also observed that the period in days required for the ratio of the hypopus reaching to above 10% became longer at the humidity increased, and the highest hypopus ratios were seen at 76 and 87% R. H., same as that observed with the populations in the diet.

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The duration of egg-larval and pupal stages, percent pupation, percent emergence, sex ratio and body weight of pupae in resistant and susceptible strains of the house fly were compared. Three strains of house flies are as follows; Musca domestica domestica CSMA : Susceptible strain; 213-ab : DDT, Pyrethrins-Resistant strain Musca domestica vicina Takatsuki : No insecticidal pressure in the laboratory LD_<50> values by the topical application method are shown in table 1. The duration of egg-larval stage of Takatsuki strain was found to be significantly longer than those of CSMA and 213-ab strains. Also, pupal body weight of Takatsuki strain was observed to be significantly heavier than CSMA and 213-ab strains.

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Survey of insecticide resistance in Blattella germanica was carried out with the insects collected from 16 localities in Kawasaki City, Japan, in the period from September 1966 to August 1967. The configuration ratio of three phenotypes, i. e. SS, RS, RR, was evaluated by the lt-p lines after contact to dieldrin residue. All the populations collected from restaurants, bars, etc. showed high resistance to dieldrin. One population from a pig pen, however, was estimated to be nearly susceptible to dieldrin. As the results of preliminary tests on diazinon resistance, all the populations were proved to be susceptible to the chemical.

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A field test of the effect of Hempa, Hexame-thylphosphoramide, C_6H_<18>N_3OP on the common housefly, Musca domestica vicina, by the milk-bait method was carried out at Sei Island in Seto Inland Sea from August to October in 1967. As the result of the test, comparatively good controlling effect of this chemosterilant on the appearance of housefly in autumn in the treated area was observed, though some problems seem to have remained in the technique of application.

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