Primary Study On The Diapause Characteristics Of Locusta Migratoria Manilensis Meyen From Reservoir Region Of Panjiakou

Locusta migratoria manilensis(Meyen) is one of the most serious pest of agriculture. Whether it is in diapause period or not by winter is an important factor which influent their propagation next year. However, it is not systemic about the research of diapause. The thesis studied the diapause characteristics of Locusta migratoria manilensis(Meyen). The results are as follow.1. According to our experiment, Locusta migratoria manilensis(Meyen)which belongs to Hebei Province Kuan Cheng population have diapause period. The diapause periods starts at the end of anatrepsis. The ovums entering diapause does not revolution, even if they are hatched under proper condition. However, there is the red belt of half-moon shape in the back-margin of compound eyes. The ovums entering non-diapause incubates under 30℃and the embryo revolution from the end of 6th day to the beginning of 7th day. After that, the red belt of half-moon shape will occur in the back-margin of compound eyes.2. The parental generation of Locusta migratoria manilensis (Meyen)are fed in the different photoperiod and temperature and the ovums are incubated under the different temperature. It is discovered that photoperiod is the major factor which induce the parental generation of Locusta migratoria manilensis (Meyen) to produce diapause ovums.Locusta migratoria manilensis (Meyen) raised in long illumination gives first place to producing non-diapause ovum. If the photoperiod is shortened, ovum's diapause rate will increase obviously. The temperature used to feed the parental generation don't have obvious effect to ovum's diapause rate. The temperature used to incubate locust ovum has an adjusting effect to ovum's diapause rate, which diapause rate is reduced above 26℃and diapause rate is increased greatly below 24℃.3. It is also found that locust ovums have very strong resistance against nature when they enter sufficiently diapause period. (1) in the field of winter resistance: when the ovums which are yielded by the locust raising 10 hours under illumination are incubated till 13 day or 17 day under 24℃, they are handled under 0℃, -5℃, -10℃. After 15 days, rate of hatch are 82.3%, 69.5%, 62.5% and 86.2%, 72.8%, 64.3% respectively. While the temperature is reduced to -15℃and -20℃, the rate of hatchability is 0 without exception. But after the non-diapause ovums are handled 15 days in 0℃and below, their rate of hatchability is 0 without exception. (2) in the respect of being able to bear cold: The non-diapause ovums hatching 6 day and 12 day under 30℃are handled on 9℃and above 50% ovums died right away after 40 day and 50 day. 100% death time is 60 and 70 day respectively. But diapause ovums have 94.5% survival rate after handling 70 day under 9℃. (3) in the respect of being able to bear dry: The ovums hatched 0 day,6day,12day on 30℃are handled 10 days under 1% moisture content condition. It is found that exceeding 50% locust ovums die. After dry treatment arrives at 15 days, the ovums produced in that very day all die, while the survival rate of the ovums hatched to to 6 day and 12 day comes down to 12.5% and 14.5%, the diapause ovums still have 41.8% survival rates. When dry treatment arrives at 20 days the non-diapause ovums developing to the 6 day incubated by 2.2% but those developing to the 12 days all die. The diapause ovums are incubated by only 7%.4. By the inquiry on developing status of the open country ovums liveing through the winter, we found that the development of locust ovums yielded in the early time before winter all stopped in the end of anatrepsis, but red belt of half-moon shape appears at back edge of compound eye; while the development of locust ovums yielded later stopped at the beginning of anatrepsis period. It was found in the inquiry after winter that only the locust ovums stagnating sufficiently before winter cound survival through winter, but those not enter diapause sufficiently would die. When the locust ovums surviving through the winter are hatched under proper conditions, disregarding spawn times before winter, they are hatched in the same time.