荔枝蒂蛀虫幼虫龄数及各发育阶段在不同温度下的发育历期

Determination of larval instars and developmental duration of each stage at different temperatures of the litchi fruit borer,Conopomorpha sinensis( Lepidoptera: Gracillariidae)

【目的】荔枝蒂蛀虫Conopomorpha sinensis Bradley是荔枝龙眼上的主要害虫,以幼虫蛀果为害。本研究旨在明确荔枝蒂蛀虫幼虫龄数及不同温度下各虫态和各龄幼虫的发育历期,为该虫发生规律、预测预报和防控技术研究提供基础生物学数据。【方法】定期收集处于不同发育时期的荔枝蒂蛀虫幼虫,测量幼虫头壳宽度,对其进行频次分析,Crosby指数验证和曲线回归分析,以确定幼虫龄数。通过室内群体饲养的方法,测定了17~38℃区间8个温度梯度下荔枝蒂蛀虫各虫态和各龄幼虫的发育历期,并采用线性日度模型对其发育速率与温度的关系进行回归分析。【结果】根据荔枝蒂蛀虫幼虫头壳宽度频次分布图,其头壳宽度的频次分布可明显分为5个区域,说明其幼虫分5个龄期,符合Dyar定律。1-5龄幼虫的头壳宽度分别为:0.092~0.120,0.140~0.206,0.217~0.319,0.356~0.523和0.582~0.728 mm。温度对荔枝蒂蛀虫卵、各龄幼虫和蛹的发育历期有明显影响,其发育历期均随温度的升高而缩短,其发育速率均与温度呈显著正相关,并符合线性回归模型。在20~32℃,荔枝蒂蛀虫可完成世代发育;在17℃时,该虫只能发育至3龄幼虫;在35℃时,蛹多不能羽化;在38℃时,卵多不能孵化。在20~32℃,其世代历期为41.16~19.34 d,蛹期为12.74~5.38 d,而产卵前期为4.75~4.22 d,温度对产卵前期无明显影响。在20~35℃,荔枝蒂蛀虫幼虫可正常发育,其1龄幼虫龄期为4.50~1.17 d,2龄幼虫期为2.09~1.40 d,3龄幼虫期为2.84~1.00 d,4龄幼虫期为3.41~1.18 d,5龄幼虫期为3.00~1.37 d,预蛹期为2.41~0.69 d。在17~35℃,荔枝蒂蛀虫卵可正常孵化,其卵期为7.73~2.09 d。【结论】荔枝蒂蛀虫幼虫分5个龄期,不同于前人所报道的4个龄期。在20~32℃温度范围内,卵、各龄幼虫和蛹的发育历期均随温度升高而缩短。本研究结果有助于荔枝蒂蛀虫预测预报方案的制定和实施。

【Aim】The litchi fruit borer,Conopomorpha sinensis Bradley,is the most serious pest of litchi and logan in China. The objective of this study is to determine the number of larval instars of C. sinensis and the developmental duration of each stage at different temperatures. 【Methods】The head capsule width of C. sinensis larvae was measured to determine the number of larval instars. The developmental duration of each stage at 17- 38℃ was determined in the laboratory via artificial rearing,and the correlation between developmental rate and temperature was analyzed through the linear regression model.【Results】The results in the frequency histogram of the head capsule width showed that the frequency distribution could be obviously divided into 5 areas,suggesting that C. sinensis has five larval instars,which follows the Dyar's law. The average head capsule width of the 1st- 5th instar larvae was 0. 105,0. 170,0. 265,0. 435 and 0. 652 mm, respectively. Temperature had significant effects on the developmental duration of egg, larva and pupa, and their durations all reduced with increasing temperatures,while the correlation between the developmental rate and temperature fitted with the linear regression model. C. sinensis could complete a whole generation from 20 to 32℃,but the larvae only developed to the 3rd instar at 17℃,few pupae could complete eclosion at 35℃ and few eggs could hatch at 38℃. The duration of one life cycle,pupa and preoviposition was 41. 16- 19. 34,12. 74- 5. 35 and4. 75- 4. 22 d, respectively. However, temperature had no effect on the preoviposition period.Appropriate living temperature for C. sinensis larvae was from 20 to 35℃. The duration of the 1st,2nd,3rd,4th and 5th instar larva and prepupa at 20- 32℃ was 4. 50- 1. 17,2. 09- 1. 40,2. 84- 1. 00,3. 41- 1. 18,3. 00- 1. 37 and 2. 41- 0. 69 d,respectively. The egg could normally hatch at temperatures from 17- 35℃,and its duration was 7. 73- 2. 09 d. 【Conclusion】C. sinensis has five larval instars instead of four instars reported in the previous research. Within the temperature range of20- 32℃,the durations of egg,each instar larva and pupa reduce with increasing temperatures. These results will provide data support for the forecast of C. sinensis.