EPOW - Ecology Picture of the Week

Victim of the Thread-waisted Wasp

Thread-waisted Wasp (unidentified species), Family Sphecidae, with caterpillar
Democratic Republic of the Congo

Explanation:  This scene is even more gruesome than it looks.

This is not just a predator-prey relationship.  This is a thread-waisted wasp, characterized by its very long abdomen attached by a stalk (or "petiole") to the thorax.  And it is doing what thread-waisted wasps do, to maintain their species.

It has not killed its caterpillar prey; it has paralyzed it with a sting.  And it is slowly, laboriously, dragging it back to its riverside sand burrow, as most thread-waisted wasps nest solitarily in the ground.  

There in the burrow, it lays an egg on the prey.  The larva feeds on the paralyzed body of the caterpillar until the larva pupates and is free to fly away to repeat the cycle of life.  (The wasp is thus correctly termed a parasitoid, not a parasite per se.  Its immature stage uses the caterpillar insect host and eventually kills it.)

Thread-waisted wasps procure not just caterpillars but also spiders, grasshoppers, and other arthropods for this purpose.  The adults can feed on the internal tissues and fluids of their prey, but also on flower nectar and honeydew from aphids.  

I was in the very remote Salonga National Park of the Congo River Basin in tropical Africa, in a clearing on the banks of the Luilaka River, when I happened to look down at my feet and saw this remarkable tiny drama unfold.  

There are over 700 species of thread-waisted wasps worldwide.  However, if you see one in your garden or yard, let it be; they can be beneficial, as they can help control spiders, especially black widows.  
  

This caterpillar had no chance!