August 8, 2009
Wasps of the genus Tachysphex (Hymenoptera, Sphecidae) hunt grasshoppers, not for themselves but as a living source of food for their larva. When they manage to catch a grasshopper it is paralysed with the stinger and then brought to a nest hole in the ground where the eggs are laid on it. This particular wasp dragged its prey up a slope of sand for over 8m (about 24′) before I lost track of it: amazing when you consider the grasshopper is twice the size of the wasp.
On one occasion I startled the wasp and it dropped its prey. It flew about and managed to relocate it, when it went through the behaviour of subduing it again. Photographs in the video show it biting at the base of the fore and mid leg coxa.
Unfortunately, I was equipped for smaller insects at the time – I had a small flash unit attached to the camera when I came across this wasp and its prey. It fairly skittered across the sand leaving me no choice by to follow after it as best I could, but with the flash being unable to freeze much of the action. Many of the photos are blurred, but the video slideshow below gives a fair representation of the journey. I lost site of the pair before I could determine if the grasshopper became ‘safely’ entombed.
May 10, 2009
This is the last of my previews of the In the Womb: Extreme Animals documentary. For me, the parasitic wasp, Cotesia glomerata, was the most fascinating of all the creatures featured.
This bizarre life cycle begins with the female wasp laying eggs in the caterpillars of the cabbage white butterfly. Eggs are pumped in and the caterpillar’s immune system responds and attacks the eggs. However, the wasp eggs are defended by a virus which are in the wasps own DNA. The virus coats the eggs which allows them to disable the immune system of the caterpillar.
About 30 eggs are laid in each caterpillar, and the wasp’s antenna can detect which has eggs and which are still available to form another surrogate womb. The wasp larva survive on the blood in the caterpillar, while avoiding the internal organs so that they do not kill their host. After 14 days it is time for the wasp larva to pupate. They cut their way out of the caterpillars body and spin silken cocoons on the still living host.
The wounded caterpillar now spins its own silk over the wasp cocoons, adding a further layer of protection. The caterpillar will now protect the wasps until it starves to death. When the wasps complete metamorphosis and emerge, the life cycle begins again.
For more information and fascinating photographic and CGI effects, see In the Womb: Extreme Animals Sunday at 7 PM on the National Geographic Channel. (Check your local listings for the time in your region)
Not exactly typical Mother’s Day fare, but perhaps it will make her realise just how lucky she is…
(CGI image of wasp larva in the caterpillar courtesy of the National Geographic Channel)
May 8, 2009
A preview from In the Womb: Extreme Animals, showing this Sunday on the National Geographic Channel. This video features a parasitic wasp (Cotesia glomerata) which uses a caterpillar as a surrogate womb: