• International Journal of Industrial Entomology and Biomaterials
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• v.5 no.1
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• pp.1-12
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• 2002

Ecophysiologically diapause represents a syndrome of physiological and biochemical characteristics, all of which ensure survival during a long period of dormancy. Since, silkworm enters diapause as embryo at the early embryonic stage, the duration of egg life depends on the duration of embryonic diapause. The nature of diapause in silkworm, Bombyx mori, is primarily determined by genetic characters and endocrinologicnl mechanisms, mediated by environmental factors such as temperature and photoperiod. Hibernating potency value besides nucleic acid and carbohydrate metabolism, production and utilization of sorbitol are also equally responsible for induction, initiation, determination, maintenance and termination of diapause. Embryonic diapause in Bombyx moir, induced by active secretion of sub-oesophageal ganglion is attributed to hormonal system and metabolic adjustment, which serves to bring about a new physiological state. Metabolic conversion of trehalose to glycogen at induction, glycogen to sorbitol at initiation and sorbitol to glycogen at termination of diapause is correlated and in each metabolic shift a key enzyme becomes active in response to hormonal and environmental stimulation. An attempt has been made in this review article to discuss briefly the nature of embryonic diapause, influence of various factors on diapause nature, hormonal mechanism of diapause besides biochemical composition of egg, nucleic acid and carbohydrate metabolism, production and utilization of sorbitol in relation to induction, determination, maintenance, initiation and termination of diapause in the silkworm, Bombyx mori.

• Korean journal of applied entomology
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• v.29 no.4
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• pp.277-285
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• 1990

Laboratory and field studies were conducted to investigate the initiation and termination factors for pupal diapause in the Oriental tabacco budworm, Heliothis assulta Guenee. Diapause induction was dependent of photoperiod and temperature experienced by 4th and 5th instar larve. One hundred percent of pupal diapause was obtained when larvae were grown at 10L/14D or shorter and $20^{\circ}C$. But at $25^{\circ}C$ the maximum rate of diapause was only about 85% at 8L/16D, the shortest photoperiod tested in this experiment. Adults, eggs or pupae did not respond to diapause-inducing environmental conditions. The critical photoperiod was 12-12.5 hr at $25^{\circ}C$and 14-14.5 hr at $20^{\circ}C$. In the field-collected sample 100% of diapuse rate was observed on Sept. 20 and thereafter in Suwon and middle part of Korea. Cold temperature treatment was not necessary in the termination of pupal diapause, but accelerated adult development.

• Journal of Sericultural and Entomological Science
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• v.27 no.1
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• pp.24-30
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• 1985

The effect of some organic solvents on interrupting diapause of Bombyx mori eggs was examined to provide a clue to the mechanism of diapause initiation. Methyl alcohol and benzene proved to be efficient in developing the prospective diapause eggs upto the stage of hatching or body pigmentation of the embryos. On the other hand, most of the eggs soaked in chloroform and mixture solution of chloroform-methyl alcohol (2:1) died in the early embryonic developmental stage with yellow or red brown colours, and the egg weights decreased upto ca. 40% of the original weight 8 days after the treatments. Methyl alcohol treatment for 2, 5 and 10 min to the 5hr-old-eggs led to empergence of the larvae, with high incidence (70∼80%) in the race of Kumchu X Chonghwa and with low indidence (1∼4%) in Daezo. The effect of same treatment to 20hr old eggs decreased to ca. 10% in the emergence of larvae in Kumchn X Chonghwa and increased to 20∼30% in Daezo, while the effect disappeared shortly after the diapause initiation (48hr-old-eggs). Considering the high dependency upon the egg age of the sensitivity to solvents, it was supposed that initiation and termination of diapause may be controlled by different mechanism. It was also suspected that the solvents exert their effect on the permeability of the eggshell.

• Korean journal of applied entomology
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• v.27 no.1
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• pp.6-13
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• 1988

Studies were carried out to investigate the diapause-sensitive stage, the effect of 20-hydroxye- cdysone on diapausing pupae and the changes in pupal proteins of the fitll webworm, HYPha¬ntria cunea Drury. The stage sensitive to diapause-inducing photoperiod lies between 5th and 15th day of the larval development. And the oxygen consumption rate of diapausebound pupae decreased to a mean level of $30mu$l $O_{2}$/g/hr. The 20-hydroxyecdysone was effective in raising the respiratory acivity of 2.5% homogenate of the diapausing fall webworm pupae and in causing a normal adult development of the diapause-bound pupae. The soluble protein content rapidly declined in normally-developing pupae, but in diapause-bound pupae it was more or less static with much higher quantity. And protein bands separated from fat body of diapause¬bound pupae were different from those of nondiapausing pupae.

• Korean journal of applied entomology
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• v.26 no.3 s.72
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• pp.139-144
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• 1987

This study was carried out to investigate the incidence and termination of pupal diapause in the fall webworm, Hyphantria cunea Drury. Larvae obtained from overwintered pupae were reared on Morus alba leaves at $25{\pm}1^{\circ}C$ with the relative humidity of 60% or higher in a laboratory. The critical photoperiod for pupal diapause initiation is between 14hrs and 14hrs & 30 minutes at $25{\pm}10^{\circ}C$. The developmental period of larvae was shorter under longer photoperiod at $25{\pm}1^{\circ}C$. In nature. diapause termination seems to begin in late December. The diapausing pupae did not emerge at all when they were transferred to a favorable environment before the time.

• Proceedings of the Korean Society of Sericultural Science Conference
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• 1997.06a
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• pp.51-72
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• 1997

Diapause hormone (DH) is a neuropeptide hormone which is secreted from the suboesophageal ganglion (SG) and is responsible for induction of embryonic diapause of the silkworm, Bombyx mori. DH is isolated from SGs and determined to be a 24 amino acid peptide amide. The cDNA encodes the polyprotein precursor from which DH, pheromone biosynthesis activating neuropeptide (PBAN) and three other neuropeptides are released and become matured. The C-terminal FXPRL-NH2 sequence of DH is essential but not sufficient for expression of full activity. Recently, we have isolated a unique hydrohobic peptide (VAP peptide) with a slight diapause egg induceing activity from organic solvent extracts of the male adult heads of the silkworm. The VAP peptide itself has no diapause inducing activity, but enhances DH activity through reducing ED50 value and the threshold concentration of DH. The DH-PBAN gene is composed of 6 exons interrupted by 5 introns and is expressed in 12 neurosecretory cells of the SG. The incubation of eggs at 25$^{\circ}C$, which induces embryonic diapause in the progeny, caused DH-PBAN mRNA content to increase at 5 different stages in the life cycle. By contrast, a 15$^{\circ}C$ incubation only induced expression of the gene at the late phrase adult stage. The temperature-controlled expression of DH-PBAN gene is closely correlated to the incidence of diapause, indicating that DH-PBAN gene expression is the initial event leading to diapause induction. DH acts to stimulate trehalase activity in developing ovary to bring about hyprglycogenism in mature eggs, a prerequisite metabolism for diapause initiation. Using in vivo and in vitro systems, DH is clearly shown to induce trehalase gene expression in developing ovaries. New protein synthesis is not needed for this process, but a Ca2+-dependent proteinkinase seems to be involved. Quite recently, we have sucessfully applied a new and potent trehalase inhibitor (Trehazoline) to reudce glycogen content in developing ovaries. The eggs deficient in glycogen were also able to enter diapause as the natural eggs do, so that we could provide the new egg system to reconsider the diapause associated metabolism other than the glycogen-sorbitol metabolic system.

• Proceedings of the Korean Society of Sericultural Science Conference
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• 2003.10a
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• pp.95-96
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• 2003

We investigated the proteins that are associated with initiation, maintenance, and termination of diapause in silkworm eggs by means of 2D-gel electrophoresis. 1. Materials : Bombyx mori: unfertilized eggs, diapause eggs, non-diapause eggs, cold-treated egges. 2. Methods: isoelectric focusing, SDS-PAGE, silver staining. (omitted)

• International Journal of Industrial Entomology and Biomaterials
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• v.23 no.2
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• pp.207-213
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• 2011

The diapause of $Telegryllus$ $emma$, the Emma field cricket, was investigated to study the ecological characteristics of the species. Changes in the volume, oxygen consumption, and water content of T. emma eggs were followed from oviposition. An increase in volume, oxygen consumption and water uptake occurred from 7 to 8 days following oviposition. The oxygen consumption of the eggs increased slowly for 7 days following oviposition, but then decreased until 15 days following oviposition. These results showed that a physiological change at diapause initiation affected the volume, water content, and oxygen consumption of the $T.$ $emma$ eggs. An experimental investigation of egg hatching showed that the eggs could be stocked at $10^{\circ}C$ for 40 days with a 14 day pre-period after laying and yield, 62.1% hatchability under these conditions. Maintaining the temperature at approximately $10^{\circ}C$ was favorable for hatching. Another experiment on egg hatching showed that the storage of eggs at $10^{\circ}C$ from 40 to 180 days would ensure satisfactory, hatching capacity.

• International Journal of Industrial Entomology and Biomaterials
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• v.15 no.1
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• pp.75-78
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• 2007

To define the molecular mechanism of initiation and termination of diapause during the embryogenesis of silkworm, Bombyx mori, mRNA transcripts from diapausing eggs and diapause activated eggs were compared with differential expression using cDNA array. Among those clones, mRNA transcript from hsp20.8A, which was expressed at a high level in diapausing eggs that had been incubated at $25^{\circ}C$ for 30 days after oviposition, whereas, in the eggs exposed to $15^{\circ}C$ for 30 days, $5^{\circ}C$ for 60 days, the expression of mRNA decreased. On the other hand, the expression of mRNA during embryogenesis observed abundantly at 4 to 6 days after heat-HCl treatment and later at 9 to 10 days after just before hatching. This result was suggested for us that hsp20.8A was expressed in response to embryogenesis as well as physical stress.

• International Journal of Industrial Entomology and Biomaterials
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• v.22 no.2
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• pp.29-37
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• 2011

Commercially managed bees are available for pollination services and are used in large commercial fields, small gardens, or enclosures such as greenhouses and screen houses. This paper describes the current status and agricultural utilization of commercially managed bumblebees as well as bumblebee rearing techniques in Korea. We surveyed the use rate and number of bumblebees for the pollination of 10 major horticultural crops and fruit trees in Korea; in 2009, the use rates were approximately 7.9% and 2.8%, respectively. The use number of bumblebees as pollinators was more than 64,345 colonies, which included 51,400 colonies for 10 major horticultural crops and 12,945 colonies for 10 major fruit trees in 2009. The value of bumblebees as pollinators in 2009 in Korea was estimated at more than 5,100,000,000 won. We also describe feeding, rearing room conditions, colony initiation, mating and diapause breaks to establish year-round mass rearing techniques of the bumblebee Bombus ignitus.