Monday, August 27, 2018

Pipe Organ Mud Dauber Wasp and Parasitic Fly

About two weeks ago, while sitting on the front porch cleaning my boots, I heard the unmistakable buzz of a female Pipe Organ Mud Dauber, Trypoxylon politum, sealing up a brood chamber inside her nest. This species of wasp uses mud to construct a long tube which it divides into individual compartments, each of which will be loaded with a collection of venom paralyzed spiders to be used as a food source for a developing wasp larva. I looked over and saw that the female wasp was in the process of sealing off the bottom chamber of a long tube nest.

I was not the only one interested in this activity. A female Tachinid fly was stalking around the entrance to the nest, waiting for an opportunity to sneak in and leave one or two of its eggs inside the brood chamber. Gaining access was not an easy process. While the female wasp was away gathering more mud, the male wasp moved in to guard the nest entrance.

Eventually, as the female wasp put the finishing touches on the bottom seal of the brood chamber, the male wasp moved away and allowed the fly to slip in.

The video above shows the female wasp bringing in mud to seal the last brood chamber, the male wasp performing its guard duty and attending to the female, and the fly skirting around the entrance to the nest and finally seizing its opportunity to enter. A longer version of this video can be seen on YouTube by clicking HERE.

Yesterday I spotted this fly resting on the outside of the tube nest. It was obviously freshly emerged and its appearance was marred only by a few crumbs of dry soil matching the color of the nest.

Not far away from the fly was the hole through which it had escaped the wasp brood chamber.

I scraped a bit of soil away from the site of the exit hole and discovered the empty pupal case left behind by the fly.

Further excavation revealed what was left of several spider carcasses and what looked to be additional fly pupae.

Here’s what was inside the chamber. There was evidence of three Tachinid fly pupae.  The larvae had feasted on the spiders, leaving only empty husks behind.

Two pupae were intact, containing flies that would probably soon be emerging. A single empty case was left by the fly I had observed earlier.

Pipe Organ Mud Daubers frequently construct their nests on my porch. Some of the holes in this nest from last season were probably made by emerging wasps, but I know that several were made by foraging woodpeckers.

Closer examination of the old nest reveals smaller holes that are just the right size for an emerging fly. I imagine this fly and wasp a game is a common occurrence on my front porch.

Tuesday, August 21, 2018

2018 Teasel Pulling Results

My Teasel removal activities took so little time this year that I can’t even describe the activity as an event.  I spent about four hours walking fields with a history of Teasel infestation and pulled all of the Teasel plants I found.  A total of about 12 acres was searched.

This is my second year of pulling Teasel plants.  Prior to that I collected ripe seed heads on an annual basis.  Last year’s effort occurred about a week prior to expected seed ripening.  This year I began pulling when most plants were just beginning to bloom.  Teasel plants stood above most other plants in the field and were easy to see.  The Teasels were widely distributed across the field as individual plants.  No clusters of plants were found.

This is last year’s harvest of Teasel plants.

This is what I collected this year from the same area, a significant reduction.  There are always a few plants that show up late in the season because they were slow to begin growth or are recovering from injury.  I’ll walk the fields again in the next week or two to search for those late developing plants, but I doubt if I’ll find many.

Pulling is now my preferred method of dealing with Teasel plants.  I can begin pulling when field vegetation is relatively short, so it’s easier to move around and find the plants.  Pulling the plant takes much less time than removing all of the seed heads.  Pulling before seeds are ripe eliminates the chance of spreading seed to other parts of the field.  I think I’ve reached the point where annual Teasel control is going to take very little of my time.  It’s nice to see the fields devoid of invasive Teasel plants.