ヒメコガネの大量飼育法について

Results of the experiment concerned with a rearing method for mass-production of successive generations of the soybean beetle were as follows.<BR>1. Use of the dried leaf mold powder for incubation bed of the eggs in a petri dish kept under wet condition ensured high hatchability, and it was favorable also to escape biting each other by hatched young larvae.<BR>2. In an attempt to improve feeding habit for rearing the first instar larvae, the dried leaf mold powder kept under 60 percent of water content was unfit to larval survival and the rate of living larvae at the 15 th day after rearing was very low. The highest suvival rate of the larvae recorded 82.6 percent when the first instar larvae reared on the modified material of leaf mold which was prepared by passing the natural material with a 6 mm mesh sieve and kept under wet condition. However, the sterile modified material of it was unsuitable to rear for the first instar larvae.<BR>3. On purpose to shorten the duration of larval stage, the second and the third instar larvae were exposed respectively at 10°C for different periods on various developmental stage after molting. When the third instar larvae were exposed to 10°C for 30 to 40 days following the 30 th day after second molting, the mean duration of their larval stage required 170 days, which was shortened about 60 days than that of the larvae treated continually at 25°C through the experiment. A low temperature treatment to the just molted larvae of the third instar influenced unfavorably for the larval development. When the second instar larvae were exposed to low temperature following the 15 th day after first molting, the duration of their larval stage shortened extremely, but their survival was considerably poor.<BR>4. Longevity of the adults reared on an artificial diet was prolonged almost twice to those on the natural fresh leaf, and they produced the eggs about three times to its number oviposited by the naturally growing adults. The artificial diet is available and able to supply easily all the year round for mass-rearing.<BR>5. Considering of the practical circumstance on space, work and cost etc. for rearing the larvae, use of the plastic cups is superior to the plastic cases in saving work and cost.