Stains for entomological microtechnique: simple stains for whole mounts and dissection

Slide mounted entomological specimens often require the aid of contrast techniques to improve the clarity of morphological characteristics. Methods can involve the use of techniques such as Phase contrast, Dark field or differential interference contrast microscopy (DIC), however where an entomologist may only have access to simple brightfield microscopy chemical staining of the specimen may be used to improve contrast. For whole mounts of entomological specimens, a single stain, occasionally two, are often used, in comparison to histological sections that often employ multiple stains in complex protocols. A number of authors have proposed different stains and staining methods for a number of insect groups with few considering the long term qualities of the stain, it has previously been shown that aniline dyes are prone to fading in Canada Balsam mounts, and that some stains fade even when protected from sunlight. This paper aims to summarise the knowledge of stains used for entomological specimens and provide details on the archival qualities.