Thread-legged assassin bug (Empicoris culiciformis)
There are so many cool facts about this week’s crawly, it’s hard to know where to begin! So let’s just start with an introduction: Meet the thread-legged assassin bug (Empicoris culiciformis).
These wee assassins (just over one-eighth of an inch) look as if they’ve been Frankensteined together with lace and parts of various other bugs.
That said, getting to see one in real life is up there with winning the lottery, mostly because they are very hard to see with their diminutive size and excellent camo. They are also mostly nocturnal hunters so they make an effort to stay concealed during the day.
There are 14 species in our pictured bug’s Genus Empicoris and only 792 sightings throughout the entire United States on iNaturalist.
When we look at our specific species, E. culiciformis, there are only seven sightings in the whole U.S. To be fair, culici (as we’ll shorten it) are essentially a West Coast species.
Still, I’ve spotted two of them, so part of finding them is knowing they exist. Also our “backyard” area overflows with riparian goodness and biodiversity, so we always have a leg up on…pretty much everyone else who isn’t us when it comes to finding cool crawlies.
Beyond beauty and wicked good camo skills, what makes culici (and their cousins) so cool?
While they are true bugs in the assassin bug Family (Reduviidae) along with 194 other species of assassin bug – they manage to stand out.
Part of their uniqueness is right there in the “thread-legged” name. Their four whisper thin back legs give them the ability to move undetected. Culici can even maneuver around on spider’s webs, and do so often.
Why would any bug hang out on a spider’s web? Seems unsafe.
If a culici is on a spider’s web, it’s actually the spider who is in danger. Culicis may be small and lacy looking, but they are true to their assassin name and dine on small arthropods – including spiders.
They will also steal a spider’s prey right out of their web as well.
Let’s back up to those legs again! When you look at our dorsal view culici photo (looking directly down on the bug) it looks like they have six thread-thin legs.
However, if you look at the photo that’s in (mostly) profile, you can see that what seem to be the front legs in dorsal view, are actually culici’s antennae and their true front legs are held up under their head.
But wait, there’s more.
Those front legs are chunkier and raptorial – like the front legs of a praying mantis. They are used in the same fashion to capture prey.
Because culicis carry their front legs up off the ground, they have a unique gait when they walk on the remaining four (recall, most insects walk on six legs). Culici step with their back left leg, then the front left leg, then the back right leg, then the front right leg, and so on. I can barely coordinate two legs, let alone four and in such a unique fashion.
The gait along with their lightness work for culicis though; they excel at sneaking up on unsuspecting aphids and other small, soft-bodied arthropods.
Their lace-like wings aren’t just for show; they do also fly, though they are so light and airy themselves, they can’t make much progress in a head wind, but can use flight to escape becoming prey and to fly to a new location when they run out of aphids.
So while you may never luck into seeing a thread-legged assassin, know that they are out there, in the dark slaying your garden enemies.