Last weekend on a hike up a local trail with my oldest daughter, we encountered one of the more interesting displays of insect behavior I have ever seen. At the top of the large, flat volcanic plateau or table there is a path about one mile long leading across to great lunch eating places on the other side. While walking on this hard, dirt path I noticed a very interesting wasp, carrying a green inch worm, land on the dirt and walk over to a small hole in the ground. This wasp then stuck its head down the hole and pulled out a small stone which was evidently blocking the hole. Then it returned to the alive but paralyzed worm and flew over to the edge of the hole. Depositing the worm on the edge of the hole, the wasp then backed into the hole, pulling the worm down with it. A few seconds later the wasp emerged, picked up the stone and put it back in the hole to block the entrance. Then it flew off in search of another worm.
As amazing as this was to watch, what I soon realized was that there were lots of wasps doing the same thing. Then all had their own hole and they all somehow knew how to get back to it every time. The wasps would fly off into the distance, only to soon return to the same hole and repeat the process. The holes all looked the same to me, spread out by the hundreds, only a few inches or feet apart, on a vast dirt path that looked the same in all locations. How on earth do they home in on their specific hole? Nature is amazing eh?
As to what was going on under ground, I can’t be sure without a nano camera, but here is my theory. These wasps were probably parasitic wasps that use the worms as a breeding ground for their young. This is actually a very common behavior, with the Tomato Hornworm being the most recognized victim of parasitic wasps. Under the ground was a female wasp ready to lay her eggs in these little green worms. The eggs would then hatch and feed on the insides of the worm, eventually emerging through the skin of the worm. Remember the movie Alien? Here are a couple more photos. I wish I had more good ones, but it was too difficult to catch the wasp in the air with a worm or its stone. A video camera would have worked well, but of course I had left that at home!