We have a strange phenomenon occurring in our backyard. It started a few weeks ago when I noticed a pair of wasps engaged in a death match on our deck in the back yard. This event happened with regularity over the next few mornings, but I didn’t think much of it at the time.
Later that week we ate outside on the deck and were impressed by the huge numbers of wasps visiting our maple tree. I should say that my husband and I were impressed; our kids were very uncomfortable.
Fast forward to last weekend when I went outside to do some internet surfing on my tablet. The first thing that I noticed was the huge number of black ants running around our deck and all over the patio chairs and table. Being a biologist I also noticed that the table was covered with aphids and that the tree was infested with them. As I sat there for several minutes, it felt like a very mild rain shower was taking place. I realized that the aphids were excreting excess sugar in the form of honeydew and that there were so many of them that the screen of my tablet was covered in aphid poo in a matter of a few minutes! I’m guessing that the ants were going wild for the honeydew and that explains why they were running frantically all over the deck and furniture. Once I figured this part of the mystery out, I was also able to see a large number of ladybugs and their eggs in the maple tree. Ladybugs love to eat aphids and were taking advantage of this buffet opportunity.
But what’s the deal with the wasps? I’m not an entomologist, but there appear to be two species visiting the tree: the common yellow jacket wasp and something that might be a bald-faced hornet. Be doing some quick reading I discovered that the adults of both of these species eat nectar, tree sap, and fruit pulp. Perhaps the aphids have made tree sap readily available by feeding on the maple tree, or perhaps the wasps are eating the honeydew waste of the aphids deposited on the leaves. The other possibility is that the wasps are preying on the aphids and chewing them up to feed to larvae back at the nest. The wasps don’t appear to be a parasitoid species preying on the aphids.
It’s very cool as a biologist to see a food web occurring in your own backyard. This phenomenon has also served to remind me of the importance of observations in solving biological mysteries and testing hypotheses.