Back in 2018, when I was working on my square meter photography project, my hopes of photographing pollinators visiting stiff sunflower plants within my plot were dashed by hordes of small brown beetles. Those beetles ravaged the flowers, eating everything that pollinators might have been interested in, and more. It was a neat phenomenon to observe, but I was also really hoping to photograph lots of pollinators on those sunflowers…
At the time, I remember wondering where the predators were. Usually, when there is a concentration of animals, predators come around to take advantage of the situation, but I never saw anything eating those beetles. This past summer, in a different part of Lincoln Creek Prairie, the situation was different. An abundance of jagged ambush bugs (great name, right?) appeared at the same time as the little beetles. Oh, and thanks to MJ Paulsen, I can report that those beetles appear to be a species of Metrioidea – a group of skeletonizing leaf beetles.
I walked around Lincoln Creek Prairie on the morning of August 16 and saw leaf beetles on numerous flowers, though not quite in the same densities as I’d seen them in 2018. I also saw ambush bugs on numerous flowers. NUMEROUS flowers. Lots of them. I don’t know where those ambush bugs were in 2018, but they sure made a dramatic appearance in 2020. And they were definitely catching and eating those little leaf beetles.
It was a beautiful morning, so I didn’t spend all of the good light photographing ambush bugs, but it was hard to avoid pass by without peering at and photographing quite a few of them. I’m not saying their abundance was a direct response to the leaf beetles emergence, but the coincident occurrence was certainly interesting. I’d be curious to hear if anyone else has noticed these beetles or the ambush bugs feeding on them.
Nature is complicated, so it’s hard to know whether ambush bugs are adapted to, or even are proficient at suppressing population booms of leaf beetles. On the other hand, predators in general – including little ones like ambush bugs – definitely play very underappreciated roles in ecosystems. The immensity of those roles goes unnoticed until predator populations suddenly decrease in number, due to disease, weather patterns, human actions, or something else.
There are lots of examples of research projects showing those cascading impacts, by either reducing predator populations on purpose or simply studying the response when it happens through other means. One of my favorites is a study I mentioned in an earlier post I wrote on coyotes. Halving the population of coyotes on a huge ranch in Texas dramatically reduced the abundance and diversity of small mammal populations, but allowed two species to skyrocket – kangaroo rats and jackrabbits. The latter of those competes with cattle for forage, which created a situation that was probably not what ranchers who shoot coyotes are hoping for.
It’s easy to root against predators when they’re eating something we think is cute, or something we’re hoping to harvest ourselves. Responding by trying to reduce predator numbers, though, has been shown countless times to be a mistake, with ramifications often much greater than the perceived impact of those predators. Again, nature is very complex, and while most ecosystems need careful management, especially these days, there is also plenty of evidence that large scale predator control efforts are usually a bad idea.
Predators have such fascinating lives and hunting strategies, it’s easy to fall in love with them. Even the ones you have to lean in closely to see are worth the trouble. Ambush predator invertebrates like assassin bugs, ambush bugs, crab spiders, and others, are particularly easy to observe and study. While they capture and kill a lot of cute butterflies and bees, they also kill a lot of beetles and other species that compete with those pollinators. What’s their overall impact? What would happen if they weren’t around? So many storylines and interconnections to ponder!