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Frozen hydrated aphid

There are more than 300 species of aphid within the UK, feeding on a variety of plants. Identification can be difficult and highly dependent upon subtle taxonomic structural features.
SEM is an ideal technique for the isolation of these features, but the aphids themselves present problems in preparation for the technique. Unlike many insects that can be readily prepared for SEM by air-drying with artefact, aphids are highly hydrated and susceptible to shrinkage and distortion.
Even critical-point-dried specimens undergo considerable gross structural changes. The abdomen shrinks and collapses and most of the thin ribbons of wax which are present on many aphid species are entirely dissolved away by acetone dehydration.
Low temperature SEM is therefore an ideal method of preparing these very delicate organisms. The images show that there is no distortion of the abdomen or any other parts of the aphid. The delicate patterns (arrows) on the surface of the abdomen (probably chitin or wax – and an important taxonomic feature) are well preserved.