The Sabre Wasp
If you find yourself in some coniferous woodland with log piles during the summer keep your eyes peeled for the huge and astonishing Sabre Wasp. You may spot it tapping on wood with its antennae in search of extremely well hidden insect larvae.
Latin name: Rhyssa persuasoria
Notable feature: The longest British parasitoid wasp. White marks along the abdomen, extremely long egg-laying tube (ovipositor) in females
Conservation Status: Not Evaluated
Where in the UK: Widespread but localised, particularly in coniferous woodland
Eating things alive
There are an amazing 5,000+ species of parasitoid wasps in the UK and the Sabre Wasp belongs to a group of them known as the Ichneumons. The name Ichneumon comes from a Greek word which means ‘ones who follow foot-steps’, referring to their habit of persistently following intended victims.
The Ichneumons lay their eggs in, or near a living host insect which is usually a caterpillar or other insect larvae. When the egg hatches the grub begins to eat the host alive, starting with their muscle tissue first, and the vital organs last. This keeps the host alive for as long as possible and therefore ensures the food supply is fresh. After this somewhat macabre act, the grub pupates and awaits adulthood. Once it emerges as an adult wasp it will likely feed on a diet of nectar or honeydew.
Ichneumons often locate their host species by ‘smelling’ them and this is exactly what Sabre Wasps do. Female Sabre Wasps locate the wood-boring larvae of the huge and beautiful Horntail Wasp (Uroceris gigas) by using their antennae to detect scents that emanate from the larvae’s wooden tunnels.
When a female Sabre Wasp has located a promising site, she starts tapping on the surface of the wood with her antennae. She then uses her long egg-laying tail to drill a ‘probe’ hole. She may drill a few probe holes before deciding on an appropriate position, and then drills as deep as she can. After 30-60 minutes, if successful, she will breach the tunnel wall, sting the larvae and then lay an egg on its body. With the larvae paralysed by the sting, it awaits the inevitable demise of being consumed alive by the Sabre Wasp grub.
As scientists learned about the amazing lifestyles of wood-boring wasps a question arose: How can such small and seemingly fragile animals drill through wood?
It turns out that the cuticle (outer ‘skin’) on their wood-boring body parts contain Zinc and/or Manganese metals, which can make up to 10% of the weight of the body part. These metals make the cuticle strong and prevent it wearing down during drilling.
Parasitoid wasps have made their cultural mark as well. The blockbuster film Alien depicted the horrors of a spaceship crew who were demonised by an extra-terrestrial which grew inside their bodies and eventually burst out of their stomachs in a flurry of blood and gore.
Even Charles Darwin was affected by their grisly habits, in writing to a friend on the topic of God, Darwin once noted: “I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae [Ichneumons] with the express intention of their feeding within the living bodies of caterpillars.”
For more info on Sabre Wasps and other Ichneumons contact Buglife directly or check out The Royal Entomological Society or The Natural History Museum.