Cassida viridis is a leaf beetle found throughout England and Wales feeding on White dead-nettle and related species; its common name is the Green tortoise beetle because, like its reptilian namesake, it can retract its antennae and legs beneath its head shield and wing case when disturbed, before tightly gripping onto the substrate. When resting on a leaf, its green colour matches the leaf and helps to avoid detection by predators.
The early growth stage of this beetle, the larva, also has fascinating methods of avoiding predation. As well as having a spiky exterior, it has a double spine-like process (which can be seen if the image of the larva is enlarged) at the end of its abdomen – faeces, as well as shed exoskeleton from previous moults, are placed onto this fork-like structure to produce a ‘faecal shield’. This faecal material also contains various chemicals originating from ingesting plant tissues, and these enhance the deterrent effect of the shield. It is suggested that the faecal shield may offer some protection against desiccation as well as the elements.
