Wizen Gil, Gasith Avital
Tel Aviv University, George S. Wise Faculty of Life Sciences, Department of Zoology, The National Collections of Natural History, Tel-Aviv 69978, Israel.
Zookeys. 2011(119):37-52. doi: 10.3897/zookeys.119.1451. Epub 2011 Jul 15.
Species identification using the characteristics of developmental stages is challenging. However, for insect taxonomy the coloration of larval stages can be an informative feature. The use of live specimens is recommended for this because the color fades in preserved specimens. In this study we examine the possibility of using variation in coloration and color pattern of larvae in order to distinguish between twoground beetlesspecies Epomis dejeani (Dejean, 1831) and Epomis circumscriptus (Duftschmid, 1812). We present an atlas and describe the coloration and body size of the three larval stages of the above species based on live specimens. An identification key is given for the three larval instars of the two Epomis species.The first instar larvae of the two Epomis species can be easily distinguished based on their color. From the second instar on, the variability in coloration and color patterns increases, creating an overlap in these attributes between larvae of the two species. Except for minor differences in color of the antennae and the base of the mandibles, larvae of the two species are indistinguishable at the second and third larval stages. To the best of our knowledge this is the first attempt to use variation in coloration and color pattern in live larvae in order to identify coleopterans. The color atlas of the larvae enables simple separation of the two Epomis species without requiring sophisticated magnifying devices, although it is less straightforward at the second and third larval stages.We found similar body lengths between the two species for all developmental stages, except for third instar larvae prior to pupation. In the two species the difference in larval body length before pupation positively correlated with that of the adult beetles. More than 70% of the adults' length can be explained by the length of the late third-instar larva; i.e. the large larvae develop into large adults. The larger specimens are the females.
利用发育阶段的特征进行物种鉴定具有挑战性。然而，对于昆虫分类学而言，幼虫阶段的体色可能是一个有用的特征。为此建议使用活体标本，因为保藏标本的颜色会褪去。在本研究中，我们探讨了利用幼虫体色和色斑变化来区分两种步甲——德氏埃氏步甲（Epomis dejeani，德让，1831年）和环纹埃氏步甲（Epomis circumscriptus，杜夫施米德，1812年）的可能性。我们展示了一幅图谱，并根据活体标本描述了上述物种三个幼虫阶段的体色和体型大小。给出了这两种埃氏步甲三个幼虫龄期的检索表。这两种埃氏步甲的一龄幼虫可以根据其颜色轻易区分。从二龄幼虫开始，体色和色斑的变异性增加，导致两个物种幼虫在这些特征上出现重叠。除了触角和上颚基部颜色的细微差异外，这两个物种的幼虫在二龄和三龄阶段无法区分。据我们所知，这是首次尝试利用活体幼虫的体色和色斑变化来鉴定鞘翅目昆虫。幼虫的彩色图谱能够简单地区分这两种埃氏步甲，无需复杂的放大设备，尽管在二龄和三龄幼虫阶段不那么直观。我们发现，除了化蛹前的三龄幼虫外，这两个物种在所有发育阶段的体长相似。在这两个物种中，化蛹前幼虫体长的差异与成虫体长的差异呈正相关。成虫体长的70%以上可以由三龄后期幼虫的体长来解释；即大幼虫发育成大成虫。体型较大的标本为雌性。
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