松墨天牛成虫雌雄体型差异及蛹和成虫大小与越冬幼虫体重的关系

【目的】本研究旨在明确松墨天牛Monochamus alteratus成虫及越冬幼虫体型大小的差异,探讨该虫越冬后成虫体型大小和越冬幼虫体重大小关系及原因。【方法】于2014年5月1日至10月31日在浙江富阳野外诱捕松墨天牛,通过测量野外诱捕到的松墨天牛成虫体长、体宽,确定林间松墨天牛成虫体型的差异;松墨天牛越冬幼虫的采集和称重测量明确越冬幼虫的组成和体重大小差异;进而通过对越冬幼虫单头跟踪饲养至化蛹、羽化,确定越冬幼虫体重大小与发育所得蛹和成虫大小的关系,阐明林间松墨天牛成虫体型差异的原因。【结果】浙江富阳野外诱捕发现,松墨天牛的活动期间很长,从5月中旬到10月初一直能诱捕到松墨天牛成虫,高峰期在6和7月份。松墨天牛雌雄成虫体型差异很大,雌虫平均体长和体宽分别为20.59±0.19和6.59±0.06 mm;雄虫平均体长和体宽分别为19.90±0.26和6.44±0.08 mm;雌虫的平均体长明显高于雄虫,但二者体宽没有显著差异;并且雌雄成虫体长和体宽呈显著正相关。越冬幼虫的头宽测定表明头宽的变化很大,最小为2.20 mm,最大为4.24 mm,经比对越冬幼虫由4龄和5龄幼虫组成;幼虫体重差异大,平均体重为304.2 mg,介于71.6~858.0 mg之间,其中5龄越冬幼虫显著重于4龄越冬幼虫。进一步将越冬幼虫单管饲养跟踪研究发现,越冬幼虫体重大小决定蛹和羽化后的成虫的大小,二者存在显著的正相关,并且由4龄越冬幼虫发育所得的蛹和成虫显著轻于由5龄幼虫发育所得的蛹和成虫。【结论】松墨天牛成虫体型差异很大,这与越冬幼虫体重差异相关;越冬幼虫的体重大小决定了其化蛹后的蛹重和羽化后成虫的体型和体重的大小;造成越冬幼虫体重差异的可能原因包括松墨天牛成虫扬飞周期长导致的产卵期长而使得天牛发育进度不一致以及寄主不同部位营养的差异。

Body size difference of male and female adults as well as the relationship between the sizes of pupae and adults and the body weight of overwintering larvae in the Japanese pine sawyer,Monochamus alteratus (Coleoptera: Cerambycidae)

【Aim】 This study aims to determine the size variation of adults and the overwintering larvae of the Japanese pine sawyer, Monochamus alternatus, and to explore the relationship of the body size of adults and the body weight of overwintering larvae of this species. 【Methods】 Field trapping of M. alternatus adults was carried out from 1st May to 31st October in 2014 in forests of Changdong, Fuyang County in Zhejiang Province, and the body length and width of adults trapped were measured with micrometer to determine the size variation. Overwintering larvae were collected also in Changdong forests in March 2014 and then taken back to the laboratory and reared with artificial diet until adult emergence, during which the weight and width of head capsule of larvae, pupal weight and adult size were recorded to analyze the relationship between the size variations of adults and the overwintering larvae. 【Results】 Trapped M. alternatus adults varied in body size. The body length and width of female adults averaged 20.59±0.19 and 6.59±0.06 mm, respectively, while those of male adults averaged 19.90±0.26 and 6.44±0.08 mm, respectively. Female adults were significantly longer than males. Furthermore, body length was significantly correlated with body width for both female and male adults. The investigation of overwintering larvae showed that M. alternatus larvae overwinter mainly at the 4th and 5th instar by measuring the width of head capsule, which ranged from 2.20 to 4.24 mm, and larval body size also varied, ranging from 71.6 to 858.0 mg with the average of 304.2 mg among which the 5th instar overwintering larvae was significantly heavier than the 4th instar overwintering larvae. Further analysis showed that the size of pupae and adults was determined by the size of overwintering larvae. Regression analysis showed that the pupal weight, adult weight, adult length, and adult width were significantly correlated with the overwintering larval weight, respectively. Pupae and adults reared from the 4th instar overwintering larvae were significantly lighter than those reared from the 5th instar overwintering larvae. 【Conclusion】 The body size of M. alternatus adults is quite varied, which is related to the size variation of overwintering larvae. Variation in larval size may be attributed to the long flight period of adults. Oviposition lasts the whole flight period, causing the difference in larval development time, and this difference as well as nutrition difference in different parts of host pine trees results in the variation in larval body size until overwintering.