Relative advantages of slide-mounted vs pinned, chalcid specimens
Author of the article:ZHANG Chen, ZU Guo-Hao, LI Er-Feng, XUE Hao
Author's Workplace:College of Horticulture and Landscape, Tianjin Agricultural University, Tianjin 300384, China
Key Words:College of Horticulture and Landscape, Tianjin Agricultural University, Tianjin 300384, China
Abstract:[Objectives] Parasitic chalcid wasps are widely used biological control agents
in agriculture and forestry and consequently have significant economic value. Because of their small size, most of their
morphological characteristics can only be observed on slide-mounted specimens.
Preparing such specimens is, however, relatively difficult, and the quality of
preparation directly affects the value of specimens for species identification
and research. This article summarizes different methods of preparing chalcid
specimens in order to provide clear diagnostic features for identifying the
species of this taxon. [Methods] Chalcid
specimens were prepared using an updated Arabic balsam sealing method, neutral
balsam (Canada balsam) sealing method and the pinning (needle-insertion)
method. All three methods are described in detail, including how to optimize
the steps of cleaning, dissection, transparency and tableting, in the
production process. [Results] The
preparation of Arabic balsam was relatively simple, complex dehydration steps
could be avoided and slides could be adjusted at a later stage. However, slides
cracked easily during long-term storage. Neutral balsam (Canada balsam) glass
slides were more permanent, but specimens were prone to shrinkage and
deformation during the dehydration process. Furthermore, neutral balsam dries
slowly, has a pungent odor, and slides are extremely difficult to readjust.
Pinned specimens retain accurate body color, grooves and other gross
morphological features, but many morphological details are hard to observe.
Furthermore, specimens are easily damaged by insects during storage. [Conclusion] Different preparation methods should be
chosen based on the size of specimen, its intended use and the degree of
ossification of the integument. (1) Specimens with body length < 2 mm should
be made into glass slides for observation and identification. The Arabic balsam
method is relatively convenient and has a high error tolerance rate, which
makes it suitable for practice and the preparation of ordinary specimens. The
neutral (Canada) balsam sealing method allows specimens to be more permanently
preserved, prevents corrosion and is highly transparent, and is therefore more
suitable for preserving type specimens of new species. (2) Specimens with a
body length > 2 mm are suitable for pinning, which allows body color and
other gross morphological characteristics to be readily observed.