Morphological characteristics for distinguishing the instars of Acyrthosiphon pisum
Author of the article:ZHAO Huai-Zhi YANG Yang ZHANG Jia-Le LI Jiang-Jie ZHAO Chuan-De SHI Yan LIU Tong-Xian
Author's Workplace:Laboratory of Insect Ecology and Molecular Biology, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, China
Key Words:Acyrthosiphon pisum; instar; morphological characteristics; cauda length; antennae
Abstract:
[Objectives] The objective of this research was to identify morphological characteristics that can accurately distinguish the instars of Acyrthosiphon pisum. [Methods] Seven morphological indices of winged and wingless morphs, including body length, body width, head width, cornicle length, cauda length, antenna length, number of antennal segments and hind tibia length, were measured under an ultra-wide area, 3D microscope. [Results] Although the morphological characteristics measured differed among both wingless and winged instars contiguous instars overlapped in all except cornicle length, which was therefore the only morphological characteristic that could reliably distinguish different instars. Hind tibia and antenna length are, however, useful as auxiliary characteristics. Additionally, the number of antennal segments can be used to differentiate between 1st and 2nd instar nymphs, and cauda shape to differentiate between nymphs and adults. [Conclusion] The instars of A. pisum can be accurately and quickly identified on the basis of cornicle length. Hind tibia length, the number of antennae and degree of cauda development also facilitate distinguishing the instars of this species.