Thursday, October 15, 2020

Jagged Ambush Bug


Ben Caruthers shared this picture with me and I was hooked. So was he as he continued the pursuit of this extraterrestrial bug which is always perched on a flower head, preferably a yellow or white blossom.  I will let him tell the story of this incredible set of his photos.


"I captured photos of some Rose Pink flowers on July 21. When I went back to edit the photos on August 9, I noticed a funny white blotch on one of the flowers. A closer look revealed a white color morph of a Jagged Ambush Bug! By the time I discovered the insect in the photo the flowers had already mostly wilted. A visit back to the flowers and general area did not reveal the ambush bug. From there forward I started paying more attention to the details of each flower photo in case I had another sighting similar to this one.

On September 19 I noticed a lot of insect activity on the New England Aster in my front yard. I waited for some good lighting and decided to try to collect some images of the participants. In that group of insects I spotted another Jagged Ambush Bug! This one displayed a more typical color pattern than the white one earlier. I collected several photos of that one example. I did not capture the insect, but I plucked the bloom that it was on and rotated it to get all angles. Then I placed the bloom next to another to allow it to move to a fresh bloom still attached to the main plant.

After thinking about it overnight I thought if there was one, maybe there would be more. I went back out again on September 20 and found two more on the same aster flowers. I took a few photos of those two with as little disturbance as possible. I also found the ambush bug from the previous day, but it had died upon the flower where I left it. 

Other naturalists on iNaturalist identified the insect on the aster as Phymata fasciata, a member of the ambush bug family Reduviidae. Ambush Bugs sit motionless on flowers, waiting to clutch other insects with their hooked front legs. Tiny and well camouflaged, they often take prey larger than themselves, including bees and large flies. Apparently the bugs I was watching weren’t hungry. I watched several bees and flies land on top of them and the ambush bug did not even flinch."


P. fasciata is a member of the Phymatinae family, called Jagged Ambush Bugs (JAB).  Their camouflage is incredible, allowing them to perch on a flower head undetected by a flower fly or bee which lands beside them.  Their powerful forelegs grasp the prey and they stab them with a beak that injects digestive juices into the insect, using what is essentially an external stomach until they suck up the goodies.

"They share many traits with assassin bugs but can be separated by their hooked forelegs with greatly widened femur sections; clubbed antennae; and widened back portion of the abdomen (so wide that it usually extends outward beyond what the folded wings cover). Most species have jagged body contours, disrupting the outlines of their bodies against the textured background of flower heads.  MDC Field Guide"

You can see Ambush Bugs in action in this Youtube video.  Then see this video where the bug is digesting a bee at least ten times its weight.

Lots of insects are called "bugs" but JAB is a legitimate member of the true bug order Hemiptera.  In this photo you can see the defining characteristic of Hemiptera, literally "half-wing."  Their forewings have two different textures—the proximal half (closest to the body) is leathery, and the distal half (away from the body) is membranous, like a fly’s wing as seen in this photo.  They have incomplete metamorphosis, meaning that the young look like wingless versions of the adult.



This is my favorite photograph.  The JAB appears to be focused on an innocent flower fly which doesn't recognize the danger.  The focus is deceiving as their eyes are compound and the black spot isn't a pupil.  

More importantly, the "JAB" is actually JABs if you look closely at the closeup crop on the right.  That is a mating pair.  I suspect if the fly got closer the male on top would leave for a post-coital snack.