中华甲虫蒲螨对寄主的选择性初探

Preliminary study on host selection of Pyemotes zhonghuajia

中华甲虫蒲螨Pyemotes zhonghuajia Yu，Zhang＆He是我国近年来发现的一种寄生性天敌，对吉丁、天牛、小蠹等林木钻蛀性害虫控制效果显著。为了解中华甲虫蒲螨对不同寄主的选择性，室内利用自制的六臂架，选取双条杉天牛Semanotus bifasciatus（Motschulsky）和沙蒿大粒象Adosomus sp．幼虫为对象，比较其对寄主种类和龄期的选择性。结果显示，对于双条杉天牛不同龄期的幼虫，中华甲虫蒲螨对1龄幼虫有明显的趋性，8h时选择1龄幼虫的蒲螨数量显著地高于3龄幼虫，之后（12～24h）选择2、3龄幼虫寄生的中华甲虫蒲螨才逐渐增多。中华甲虫蒲螨对双条杉天牛和沙蒿大粒象的2龄幼虫随着时间推移也表现出不同的选择性，中华甲虫蒲螨接人六臂架内8～12h对双条杉天牛表现出明显的偏好，差异显著；24～36h逐渐倾向于沙蒿大粒象，第48小时选择沙蒿大粒象的蒲螨数量显著地高于双条杉天牛。上述结果说明，中华甲虫蒲螨对不同寄主和同一寄主不同龄期的幼虫有明显选择性，并且在不同时间段选择差异会有显著变化，倾向于选择龄期较低、表皮硬度低、活动能力低的幼虫。

Pyemotes zhonghuajia Yu, Zhang ＆ He is one of several species of recently discovered natural parasites which have been broadly applied in biological control of forest wood borers in China, such as Buprestidae, Cerambycidae and Scolytidae. In order to determine the host preference of P. zhonghuajia, experiments were conducted indoors using a specially constructed six-armed frame. Two species of pest larvae, Semanotus bifasciatus （Motschulsky） and Adosomus sp. were used to assess host species and host instar selection by the parasite. It was found that female adult mites displayed signficant orientation towards first instar larvae of S. bifasciatus, Within 8 h, the number of female adult mites choosing 1^st instar larvae was significantly higher than those choosing 3^rdinstar larvae. After 12 -24 h, the number of female adult mites choosing 2^nd and 3^rd instar larvae increased. Differential selection of 2^nda instar larvae of the two host species was also observed. The mites showed a significant preference for S. bifasciatus over Adosomus sp. during an 8 - 12 hour period in the six-armed frame. After 24 - 36 h the mites inclined towards the larvae of Adosomus sp. , showing a significant difference at 48 h. It is concluded that P. zhonghuajia shows obvious selective preferences for host species, as well as for specific instars of that host, but that these differences change significantly with time. The mite prefers early instar larvae when their skins are soft and hosts which display low activity.