光肩星天牛幼虫排粪规律调查

天牛幼虫排出的虫粪在指示天敌寻找寄主的过程中起着重要的作用。通过在光肩星天牛幼虫发生期定期收集幼虫虫粪的方法,首次研究了林间天牛幼虫排粪量的变化规律。结果显示,光肩星天牛成虫羽化前,排粪总量呈现由上升到下降的过程,单个排粪孔的日平均排粪量为(0.030 2±0.002 1)g,单排粪孔的日最大排粪量可以达到0.319 4 g。同时研究了幼虫排粪量与寄主树的胸径、树皮厚度、树皮含水量和排粪孔大小的关系,结果表明,在调查期内,无论是各个排粪孔的排粪总量还是日均最大排粪量,均与排粪孔的大小有直接关系,而与其他几个因子无关。通过在树干上缠绑胶带形成的微栖境,采集到了光肩星天牛的天敌花绒寄甲成虫,表明花绒寄甲的发生与寄主天牛的发生紧密相关。

Study on Frass Extruded by Larvae of Anoplophora glabripennis

Frass of longhorned beetle larvae plays an important role in natural enemies searching for their cerambycid hosts. By periodically collecting larval frass of Anoplophora glabripennis in field from April to June, the quantities of frass extruded by longhorned beetle larvae were studied. The result showed that the quantity of frass extruded by larvae firstly increased then decreased during investigation period before adult emergence. The average quantity of frass per hole per day was (0.030 2±0.002 1)g, and the maximum of frass quantity per hole per day was 0.319 4 g. The relationship between frass quantity, diameter at breast height of host tree, thickness and water quantities of bark, and diameter of frass-extruded hole were studied. Results showed that total frass quantity or maximal frass quantity per day of every frass-extruded hole only had direct relation with the size of hole during investigation period and were independent of other factors. In order to collect frass during investigation, adhesive tapes were used to cover frass holes, so micro-habitats under tape were established. More than thirty adults of Dastarcus helophoroides, an important natural enemy of A. glabripennis, were collected under tape during the investigation period. Results indicated that occurrence of D. helophoroides were consist with host mature larval stage or pupae stage for more parasitizing chances.