A Beautifully Bejewelled Predator - the Ruby-tailed Wasp

Look carefully on sunlit walls, old dead tree trunks or anywhere that solitary bees may nest, and you may be lucky enough to spot one of these beautiful little wasps. Often called Ruby-tailed Wasps or sometimes Jewel Wasps, these are parasitic "cuckoo" wasps that lay their eggs in the nests of other solitary bees or wasps, such as the Red Mason Bee, Osmia bicornis (=Osmia rufa).

Classed a parasitoids (as they actually kill their hosts), these wasps are in the Family Chrysidae. There are several species in the UK, the commonest being Chrysis ignita. They can be difficult to tell apart though, but all are characterised by having a brilliantly-coloured metallic-like cuticle in iridescent blue, green and red. The cuticle is also very tough, thought to provide some protection should they be attacked by their host bees or wasps. Some also have a concave abdomen that enables them to roll into a protective ball.

They are often very active and somewhat challenging to photograph, as they investigate potential host nest sites. Their antennae are constantly "twitching" as they search, helping them to detect potential nest sites. Once found, they will check that the host adult is absent and then enter the nest hole to lay their own eggs. Later, the Ruby-tailed Wasp larvae will hatch and devour the host's egg or larva and then the food stocks. They then complete their development and emerge as adults next season.



Above (left and right), Ruby-tailed Wasps showing typical colouration and down-turned antennae. Centre - a Ruby-tailed Wasp investigating an old screw hole in my house wall. Posted on Day-6 of National Insect Week.