Recently, a video has been going somewhat viral online about “strange bugs” that have, apparently, “baffled NASA scientists”.
I don’t know which of NASA’s scientists were looking at these insects – I am sure there are some NASA entomologists somewhere, but I have no idea if they were consulted! If we’re actually talking about physicists and engineers, I think they can be forgiven for focusing their expertise on looking after astronauts, etc.! Now, I’m not especially familiar with the insect fauna of the USA, but here are my two pennies (or two cents?) on the “mystery”:
1. The insects look to me like nymphs of Hemiptera, probably Pentatomidae (shieldbugs). For comparison, here‘s a picture of a nymphal Southern Green Shieldbug/Stinkbug, here‘s the Brown Marmorated Stink Bug nymphs (so cute!) and here is the nymph of the Heather Shieldbug. While perhaps not identical to the insects in the video, the general appearance is broadly similar.
So what are they up to? In the video they seem to walk around in formation, sometimes circling, other times lining up.
Let’s think about what shieldbugs do in their day-to-day life. Mostly, they potter around on plants, especially walking up and down stems, feeding on plant material (usually – there are also some predators in this group). When you’re walking along a twig, it’s useful to know where the twig is leading you, when it comes to an end, and whether you’re about to hit the main stem or a leaf or something. A good way of doing this can be to grow a pair of long, waggly antennae and wave them about in front of you.
Indeed, it’s fairly normal for insects to display thigmotaxis, which is basically described the insect modifying its behaviour in response to a touch stimulus. It’s not just insects that do that – if you’ve ever had an infestation of mice, you’ve probably noticed they tend to hang around skirting boards and rarely make a full on dash across a large kitchen. Partly, these sorts of behaviours are mediated by keeping a sensitive body part (in an insect’s case, often antennae or legs; in a mouse’s case, probably whiskers) touching a nice solid, reassuring wall or twig.
When you’re doing behavioural entomology, this can be a bit of a pain in the proverbial. For a piece of kit like a four-arm olfactometer, it’s not entirely helpful when the insect whose odour preferences you’re trying to determine instead seems more interested in walking continuous loops around the outside of the olfactometer chamber. Other devices like locomotion compensators attempt to overcome these problems by removing all the edges from the setup.
In any case, how might this manifest in thigmotactic insects suddenly thrown into a place where there are no nearby edges, only some conspecifics? This leads to…
2. In an attempt to find an edge, perhaps our Mystery Texan Bugs (for bugs, indeed, they seem to be) are antennating the area around themselves and when they find a solid object – the tip of a friend’s abdomen – they follow it. It could be that there are also odour cues that make the abdomen tip especially attractive (if you’re walking along a twig, single-file is probably the way to go). This would result in behaviours like following each other in circles and attempted entomological conga lines (a behaviour that may also be occasionally observed after conference dinners at Ento conferences…).
So in conclusion, their behaviour and appearance is fascinating and lovely, but my personal opinion is that it’s not that surprising. We might have to look a bit harder for alien life… Especially when such marvels don’t require going much further than a suburban back garden.
Update: Apparently the Mystery Bugs have been identified as Homaemus proteus – which is indeed a species of shieldbug. Here are some more photos of the first instar nymphs, and here is the adult. What’s probably most remarkable is that it’s in the group Scutelleridae, which is the metallic shield bugs – H. proteus is actually pretty dull compared to some closely related species.