This is the nymph of an assassin bug known as the Masked Hunter, Reduvius personatus. It’s alive and healthy and is looking just as it should. The predatory bug excretes a sticky substance that traps dust and debris. The result is a highly effective camouflage and an odd looking bug.
I first found this non-native insect many years ago while I was sweeping the concrete floor of my barn. Before I could get the dust pan in position to collect the pile of dirt, several lumps crawled free and took off across the floor. Until I learned the truth, I believed that their dust covered condition was a result of being swept up, although it seemed odd that they would end up so completely covered.
The Masked Hunter preys on a variety of small insects and other similarly sized arthropods. The fact that Bed Bugs are near the top of its list of favorite foods makes people believe that the presence of the Masked Hunter indicates a Bed Bug infestation. This may be true if you keep finding them in your bedroom, but they are most often encountered in barns and other outbuildings. In those locations, the Masked Hunters may be feeding on other Bed Bug species or one of the many other prey items they are known to consume. I’m normally unhappy at the presence of non-native species, but this one seems to confine itself to man-made structures and that just doesn’t seem quite as bad.
I don’t know if the dust covering just naturally accumulates as the bug travels around its preferred habitat or if the bug actually applies the bits to its body. Whichever the case, the process must be repeated after each molt. The use of debris camouflage ends when the bug reaches the adult stage. I’ve seen the shiny black adults, but it took me a while before I realized that they came from the dirty nymphs.
It seems that the dust covering would hinder the bug’s sensory abilities. This is apparently not the case since it will seek cover at my approach and its continued presence is evidence that it is an effective hunter. Like many other Assassin Bugs, this one is said to inflict a painful bite if mishandled. I’ve chased a few onto my hand without incident, but I’ve since stopped doing that. Most insects will walk on your hand without biting or stinging if they are allowed to move freely. It’s when you close your hand or otherwise restrict them that they are likely to defend themselves. There have been enough times when innocent appearing insects have just given me a bite that I no longer offer the really painful biters that opportunity. I don’t imagine that I’ll ever eliminate dust and dirt from the barn, so these guys ought to be around for a long time.