Malachius bipustulatus - Male antenna w. excitators
The males of Malachite beetles (Malachiidae) carry excitatory glands ("excitators") on their body - special organs that attract females. In the various genera these excitators are located at different positions on the body. In Malachius the excitators are placed on the first antenna segments, making it easy to recognize males of Malachius by these conspicuous protuberances.
An example of excitators on the tip of the fore wings can be seen here:
More images of same individual:
''Malachius bipustulatus'', the malachite beetle, is a species of soft-winged flower beetles belonging to the family Melyridae subfamily Malachiinae. In case of necessity, this beetle can release a smell that deters predators. The males attract females producing special secretions from its antennae.