Crawlies with Cri: jumping spider

Marchena Minuta – Jumping spider

This week’s crawly is so small. (How small is it?) It’s so small it has “minuta” right there in their name. Meet the Marchena minuta jumping spider.
Literally, how small are they? Marchena top out at just over one-eighth of an inch. That’s small. Really, really small. Go grab a ruler or tape measure and see how small that is, I’ll wait.
So small, right?
Marchena also have a small range. They can be found in Oregon, California, Washington, Montana, Idaho and Nevada. They aren’t found very often.
There are seven recorded marchena sightings on Bug Guide and 48 on iNaturalist. Of “all” those sightings six are in Oregon. That said, I can add two more, because I’ve found two of them, but never uploaded the sightings. Still, that brings Oregon to at least eight sightings – go us!
It can safely be said there are far more than eight marchena living in Oregon right now, but they are tricky to find. Their micro-mini size makes them hard to spot. Even if you can spot one, it’s difficult to identify field marks when they are on a one-eighth of an inch critter.
Brief pause for a definition: A field mark is a visible mark or characteristic that can be used in identifying a bird or other animal in the field.
The biggest challenge to spotting a marchena, however, is their habitat of choice. These itsy-bitsy spiders hang out almost exclusively in conifers generally on the trees’ trunks. You can see how our pictured male’s color and pattern camouflage would make him seamlessly blend into pine, fir or cedar bark. Or moreover, he could just hole up in the teeniest crevasse or crack on the trunk or branch of a conifer tree.
Still, enough entomologists have found enough marchena that they’ve learned some super cool things about one of Oregon’s littlest animals.
Marchena are one of the few jumping spider species (out of the 315 species in North America) who have a stridulatory mechanism.
A what now?
A mechanism that allows them to stridulate.
Still not helpful?
To stridulate is to make a shrill creaking noise by rubbing together special bodily structures. Like how crickets chirp!
Marchena males make noise by rubbing the inside of their frontmost legs against the rugose sides of their bodies.
“Rugose” means wrinkled or corrugated.
Basically marchena are little “one man bands” specialize in “washboard.”
Of course, there’s still some mystery to the stridulation of marchena. Entomologists aren’t sure if marchena make music to attract mates or to communicate with other marchena or maybe both.
The communication stridulation function would make marchena even more unique among jumping spiders than its small size and ability to stridulate at all. Most species of jumping spiders are solitary spiders, but marchena may be a communal species.
Again, their size and relative rarity make them a challenging species to study, but one day we may get a definitive answer as to whether marchena are misanthropes or party animals.