The immigrant populations of Hyphantria cunea in Japan are variable in larval colour, ranging from light yellow to black in the last instar. In the native country (North America) a similar variaiton has been described, and temperature has been known as a factor involved However, the seasonal variation in larval colour that is found in the invading bivoltine populations is not accounted for by this factor alone. The results of laboratory experiments demonstrated that photoperiod was a main factor causing the seasonal variation in colour. At 25°C there was an abrupt shift in coloration around a photoperiod of 14 hr 45 min. Photoperiods shorter than this predominantly gave melanistic larvae while those longer than this produced a small number of such ones. A few light-coloured larvae occurred only at photoperiods of 15 or 16 hr. It was also found that a high temperature was comparable in its effect to a long photoperiod and a low temperature to a short photoperiod.

View full abstract

The relationship between the mean monthly normal temperatures at 116 geographical locations in Japan and the minimum temperatures below which development ceases was established theoretically for major species of stored product insects. In unheated premises monthly mean temperatures of 17°C or higher were considered minimum for the development o most injurious stored product insects including Callosobruchus chinensis, Sitophilus spp., Cadra cautella, and Plodia interpunctella, 20°C or higher for Tribolium spp., Oryzaephilus surinamensis, and 24°C or higher for Trogoderma granarium, Rhizopertha dominica, and Cryptolestes ferrugineus. From these relationships the number of months when storage premises have conditions favorable for the development of certain species or groups of species were calculated for various areas in Japan. Maps based on these evaluations show that Sitophilus and most other stored product insects can cause serious problems throughout Japan except in the central and northern part of Hokkaido. Rhizopertha dominica can attack stored food in Sikoku, Kyushu and the soluthern coastal areas of south-west Honsyu. But the severity of its infestation is likely to be minimised due to competition from Sitophilus spp. Triborium spp. and O. surinamensis are likely to occur in all parts of Japan except Hokkaido and most of north central Honsyu. Trogoderma granarium, because of its need for hot and dry conditions and pressure of inter-specific competition from Sitophilus spp. and R. dominica, was thought unlikely to be a serious pest of stored grain in most areas of Japan except in large warehouses along the coast of Seto Inland Sea, especially around Kobe and Kure.

View full abstract

Morphological observations on Ceroplastes pseudoceriferus GREEN, one of the common scale insects in Japan, were carried out throughout the postembryonic development with a special interest on the relations of the dermal gland pores and ducts to the wax secretion. The progress of morphological changes during the development from the first instar larva to the adult was described in detail, with reference to the external appearance of the waxy coverins of each instar. The dermal gland pores and ducts could be classified into six types : Simple pore, cuciform pore, quinquelocular disc pore, multiocular disc pore, tubular duct and filamentous duct. On the basis of the distribution and the time of apperance on the body surface it is inferred that the simple pore is responsible for the secretion of wet wax which is produced after the third instar, the quinquelocular disc pore for powdery was in the stigmatic furrows, and the multilocular disc pore for powdery wax around the vulva. By the method used, no type of pores or ducts which are responsible for the secretion of dry wax in the first and second instars, was found.

View full abstract

The patterns and changes of nucleic-acid synthetic activity during the course of nuclear-olyhedrosis were demonstrate in the fat body and some other tissues of the silkworm larva (Bombyx mori L.) by means of autoradiography with tritiated thymidine and uridine as nucleic-acid precursors. The results indicated that both activities of DNA and RNA syntheses in the infected nucleus of the fat body increased progressively up to a point just prior to the polyhedra development. Beyond this period, there was a sudden breakdown of DNA synthesis, while the activity of RNA synthesis decreased gradually with the polyhedral growth. Some of the newly synthesized RNA in the diseased nuclei seemed to be adsorbed onto polyhedra during their formation. Essentially the same pattern of nucleic-acid synthesis was noted in the other infected tissues such as hypodermis, muslce and tracheal epithelium.

View full abstract

The bioasasy experiments were carried out with pyrethrum alone and the pyrethrum synergised with piperonyl butoxide, MGK-264 and a mixture of both the synergists. The median response concentrations calculated and the regression lines drawn, indicate that MGK-264 is slightly inferior to piperonyl butoxide as pyrethrum synergist, but if the cost of MGK-264 is taken into consideraiton, it appears to be more economical than piperonyl butoxide. A mixture of piperonyl butoxide and MGK-264 appears to be a better synergist on being mixed with pyrethrum and the mixture may be prepared at a saving cost, because of the lower cost of MGK-264.

View full abstract

By means of agar gel electrophoresis esterase zymograms of extracts from various tisues, singulary of individual larvae, were compared using a number of silkworm strains. Six major bands moving toward the anode were found with β-naphythyl acetate as the substrate and naphthanil diazoblue B as coupler. The fastest migrating intense bands A and B were detected in the mid-gut, and the less mobile esterase C was present in the silk gland. Esterases (E, F) detected in tracheas completely corresponded to integument esterase types. This phenomenon suggests that esterase bands in the integment and tracheas may be controlled by the same genes. The bands detected for the esterases in the integument correspond with the slow migrating bands of the Malpighian tubules. No similarity was noted among the esterase patterns obtained for the blood, mid-gut and silk gland and those of the integument or tracheae.

View full abstract