垂叶榕果内寄生瘿蚊的发生规律

Occurrence pattern of an undescribed gall midge in the fig of Ficus benjamina

在云南西双版纳热带地区,一种还未被描述属和种的瘿蚊寄生于垂叶榕果内的雌花子房里,并膨大形成虫瘿,靠取食花胚组织完成发育。通过2010年定时定点的系统观察和研究瘿蚊的发生规律,结果发现:该种瘿蚊在垂叶榕上发生频率较高,抽样的18批果有17批被瘿蚊寄生,其中有13批果的寄生比率超过了60%,部分甚至达到100%。瘿蚊寄生雌花的平均比率不超过6%,平均每个榕果内有瘿蚊1～40只不等。瘿蚊寄生不仅降低了垂叶榕的种子数,还致命性地影响着传粉榕小蜂的繁殖。在对瘿蚊的羽化、交配行为及其成虫的活动规律观察中,结果显示:寄生在一个榕果里瘿蚊需要5～7 d才能羽化完,其羽化高峰期出现在第2～3天;一天内羽化的高峰出现在上午8:00—10:00及晚上20:00—0:00;而羽化后瘿蚊活动高峰期出现在上午8:00—11:00。雄蚊会帮助雌蚊离开榕果并优先获得交配权,雌蚊交配后飞离繁殖自身的榕树,去寻找适合产卵的榕果繁殖后代,雄蚊不离开羽化树,而死在繁殖自身的榕树附近。这些结果为深入研究瘿蚊的防治技术提供了科学依据。

In Xishuangbanna tropical region, an undescribed species of gall midge on Ficus benjamina lays its eggs in the ovary of female flowers, producing a large gall in which the larva feeds on the gall＇ s tissue to complete its life cycle. We investigated the occurrence of gall midge on F. benjamina through systematic sampling at a fixed time and location in 2010. Eighteen crops were sampled and gall midges found to occur in 17 of them. The percentage of figs attacked by gall midges was over 60% in 13 of the crops, reaching as high as 100% . Gall midges parasitized only up to 6% of female flowers and on average produced fewer than forty individuals in a single fig. The occurrence of gall midges reduced the number of seeds produced and had a deadly effect on the reproduction of pollinators. We observed the behaviour of eclosion, mating and flight of the gall midge. We found that all gall midges colonizing a single fig took 5--7 days to complete eclosion, and that the eclosion peak appeared in the 2nd--3rd day. In one day, eclosion peaks occured at 8：00-- 10：00 in the morning and 8：00--12：00 at night. The peak of activity after eclosion was at 8：00--11：00 in the morning. Male gall midges emerged first and assisted female gall midges to emerge. Once a female had emerged, a male would mate with her. Female gall midges left the natal fig trees after mating to search for appropriate trees for egg-laying. However, after mating, male gall midges died under the natal trees. Our results provide a basis for future study of the technology of gall midge control.