Department of Entomology, Michigan State University, East Lansing, MI 48824, USA.
J Econ Entomol. 2011 Feb;104(1):81-6. doi: 10.1603/ec10283.
The biological control agent Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) is a gregarious larval endoparasitoid of the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an invasive cambium-feeding species responsible for recent, widespread mortality of ash (Fraxinus spp.) in North America. T. planipennisi is known to prefer late-instar emerald ash borer, but the cues used to assess host size by this species and most other parasitoids of concealed hosts remain unknown. We sought to test whether vibrations produced by feeding emerald ash borer vary with larval size and whether there are any correlations between these cues and T. planipennisi progeny number (i.e., brood size) and sex ratio. The amplitudes and rates of 3-30-ms vibrational impulses produced by emerald ash borer larvae of various sizes were measured in the laboratory before presenting the larvae to T. planipennisi. Impulse-rate did not vary with emerald ash borer size, but vibration amplitude was significantly higher for large larvae than for small larvae. T. planipennisi produced a significantly higher proportion of female offspring from large hosts than small hosts and was shown in previous work to produce more offspring overall from large hosts. There were no significant correlations, however, between the T. planipennisi progeny data and the emerald ash borer sound data. Because vibration amplitude varied significantly with host size, however, we are unable to entirely reject the hypothesis that T. planipennisi and possibly other parasitoids of concealed hosts use vibrational cues to assess host quality, particularly given the low explanatory potential of other external cues. Internal chemical cues also may be important.
生物防治剂四纹豆芫菁（膜翅目：长尾小蜂科）是一种绿斑萤叶甲（鞘翅目：扁甲科）的群居幼虫内寄生蜂，绿斑萤叶甲是一种入侵的形成层食性物种，导致北美近期广泛发生的白蜡树（Fraxinus spp.）死亡。已知四纹豆芫菁更喜欢绿斑萤叶甲的晚期幼虫，但这种物种和大多数其他隐蔽宿主寄生蜂用来评估宿主大小的线索仍然未知。我们试图测试绿斑萤叶甲幼虫在进食时产生的振动是否随幼虫大小而变化，以及这些线索与四纹豆芫菁后代数量（即育雏大小）和性别比例之间是否存在任何相关性。在将幼虫呈现给四纹豆芫菁之前，我们在实验室测量了不同大小的绿斑萤叶甲幼虫产生的 3-30 毫秒振动脉冲的幅度和频率。脉冲频率不因绿斑萤叶甲大小而变化，但大幼虫的振动幅度明显高于小幼虫。与小宿主相比，四纹豆芫菁从大宿主中产生的雌性后代比例明显更高，并且在之前的研究中表明从大宿主中产生的后代总数更高。然而，四纹豆芫菁后代数据与绿斑萤叶甲声音数据之间没有显著相关性。然而，由于宿主大小与振动幅度有显著差异，我们无法完全拒绝四纹豆芫菁和可能其他隐蔽宿主寄生蜂使用振动线索来评估宿主质量的假设，特别是考虑到其他外部线索的低解释能力。内部化学线索也可能很重要。
