Salticid Snapshots

Saltation – from Latin, saltus, meaning "leap", and since jumping spiders lack extensor muscles at their leg joints they accomplish their amazing leaps by suddenly increasing the blood pressure to their fourth pair of legs. The precision of their predatory pounces is guided by their large AME – Anterior Median Eyes – the acuity of which are ten times better than the huge compound eyes of a dragonfly.

This pretty little female spider goes by the name of Marpissa formosa. She was found on the doorframe of a car and had probably been hitchhiking there for the past hour, hanging on for dear life. The reflective paint made a poor background, as did some red granite, but she obligingly jumped up and posed on my hand.

Male spiders are often much smaller than females; that's not the case here, both sexes were about 10 mm give or take. But they certainly are colored and patterned differently, and without a field guide or seeing a mating pair of spiders one would never guess that the male Marpissa formosa in the next two pictures is the same species as the female above.

Phidippus princeps (from Latin, meaning "first, chief, sovereign") is also roughly 10 mm long but much more robust. The salticid habit of always turning to face danger with those AME makes it difficult to acquire shots from different angles. In this case it presents this male's field marks quite nicely – white scaling on the palps, white fringes on the legs and blue-green chelicerae. The abdomen can vary between individuals and instars and isn't reliable for identifying this spider.

Like its cousin Phidippus audax a.k.a. the Bold Jumper this spider was totally fearless. He leaped at the camera, jumped on my hand (but of course didn't bite), and his last leap took him ... in my shoe? inside the leg of my pants? or he missed me and went into hiding? ... I'm not sure which.

A couple of Phidippus princeps females – again, there's not much difference in size between the sexes, but even so the females tend to be more robust than males. A good rule of thumb for sexing arthropods in general is "Eggs are bigger than sperm." In addition the males carry their sperm packets in specially modified pedipalps, the profile of which is unique to each species. The palps of females are unmodified, bristly and resemble short legs.

Phidippus princeps is as big as our local jumping spiders get, but the Regal Jumper (Phidippus regius) can attain a length of about 20 mm – large enough to tackle more than the standard menu of insects and other arthropods.

At the other extreme in terms of size is the diminutive Peppered Jumper (Pelegrina galathea). Attaining a length of only about 3 mm this mating pair of spiders was at the limit of the camera's macro.

The pair separated amicably after mating. The female fled the scene immediately but the male hung around for a minute and I was able to get a few photos for future reference.

A male Eris militaris a.k.a. Bronze Lake Jumper looks superficially similar to male Peppered Jumper, but it lacks the strong annulations on the legs, the branched white markings on the cephalothorax and the spots near the tip of the abdomen. In addition the Bronze Lake Jumper is about twice the length of the Peppered Jumper.

The vision of this small arthropod is amazing in proportion to its size. The male recognized a female of his species from a good 30 cm away and started signaling to her by wagging his abdomen and waving his modified front legs, making her aware of his intentions from a relatively safe distance. A necessary prelude to mating, because with their hair-trigger killer instincts jumping spiders will tackle anything that moves and looks small enough to overpower and eat.

The female is a few millimeters longer than the male and much heftier. She did have dinner on her mind, albeit a midge rather than her prospective mate, wasn't receptive to his advances, and no mating took place. So although the markings are correct for an Eris militaris female there are other jumper look-alikes and it's not possible to conclusively say these two spiders were the same species.

The attractive spider in the next group of photos is a female Dimorphic Jumper (Maevia inclemens), she's about 8 mm long.

This looked like a dramatic opportunity to acquire a dramatic shot of the spider catching dinner but it turned out to be something better. The spider homed in on the ant and started to leap but then aborted it, and when I looked at the image on the computer screen I saw why. It looks like the ant was threatening to (or maybe did) spray formic acid or some other nsty chemical at the spider.

Male Dimorphic Jumpers are two to three millimeters smaller than the females. Its small size combined with cryptic markings made this one almost impossible to see against the background of lichen encrusted stone. The males come in two color forms, here's an image of the other variation at BugGuide.Net.

Always look twice – I jumped to the conclusion that these itsy-bisty mottled brown spiders, only about 3 mm in length, were the immature instars of a species I was already familiar with, perhaps Salticus scenicus.

Not so ... one of the spiders became agitated at my presence and waved its palps around, whereupon it became obvious that this was a fully mature male.

Sometimes immigrant species die out because conditions simply aren't right for them in their new habitat. They may – like the ubiquitous primate Homo sapiens – find themselves in an favorable environment with a plentitude of food and lacking the limiting factor of predation, overpopulate their habitat and outcompete the native species, in which case they get bad press and have epithets like "invasive" hurled at them. Or, like the Asian Jumping Spider (Sitticus fasciger), they can blend into the background, fit right in, and live their little lives, doing what spiders do best ...

"If it is not small enough to eat nor large enough to eat you, and doesn't put up a squawk about it, mate with it." ~ (David L. Jameson, Systematic Zoology, 1955) ... that pretty much sums up the lifestyle of jumping spiders, and the rest of nature as well.

It only took about 300 million years ...

... for the forces of natural selection to produce spiders. Silk-producing arachnids go back even farther (nearly 390 million years), and chelicerates – distant cousins of spiders – were among the first animals to leave the sea and conquer dry land. Of the roughly 40,000 species of spiders in the world about 5,000 belong to the family Salticidae, the jumping spiders.

Jumpers are fun spiders to watch. Unlike the orb weavers which simply hang in the middle of a web waiting for a meal to come to them, jumping spiders actively hunt for their dinner – they almost seem to have character. The sturdy female spider in the next two pictures is a Phidippus whitmani. A photo of a male, which is a striking bright red rather than brown, would have brightened up the color scheme.

The average Phidippus clarus in my area also tends to be a rusty brown but this summer I was lucky and stumbled across several males that were a beautiful red. It's tough to get a dorsal shot of that abdomen, as jumping spiders have a habit of facing toward the camera, aiming those arresting anterior median eyes at whatever they perceive to be a threat. See what I mean about character?

Phidippus clarus is a good sized jumping spider about 10 mm long, my finger to the left in the photo gives a sense of scale.

A male Marpissa formosa basking on the rocks along the river shoreline, also about 10 mm in length but elongated and lean rather than robust.

I was at unable to identify the male spider in the following three images. Despite its length of 6 mm and the shape of the carapace being completely wrong, I nevertheless – tentatively, reluctantly, unhappily – called it a "crab spider" (male crab spiders are tiny, much smaller than 6 mm). This diagnosis was less than satisfactory so I submitted the images to the always helpful people at BugGuide.Net, and it turns out that my "crab spider" is an old friend ...

... Araneus trifolium, the Shamrock Orbweaver. (The little red hitchhiker on the spider's abdomen is a parasitic larval mite, family Erythraeidae.) As is often the case with spiders the male is much smaller than the female, the old girl in the photo below is a good 25 mm in length, and gravid, ready to lay eggs any time. Talk about sexual dimorphism ... looking at these two spiders, who would guess that they were the same species?

This is a white form female, and if the difference between the male and female aren't enough to cause confusion, female Shamrock Orbweavers, a.k.a Pumpkin Spiders, come in an awesome array of colors!

Whilst they don't come in a baffling variety of tints and hues, Flower Crab Spiders such as Misumena vatia can change their color from yellow to white in order to match the color of the flower they are lurking on. Obviously the Flower Scarab (genus Trichiotinus, itself an accomplished bee mimic) is unaware of how perilously close it is to its possible demise ...

Although many species of wasps are parasitoids of spiders, the Thread-waisted Wasp (Ammophila sp.) provisions its larvae with caterpillars and this wasp was simply stopping at these False Solomon's Seal blossoms for drink of nectar, not hunting the spider as a potential source of nourishment for its young.

But Flower Crab Spiders blend into the background so well they are virtually invisible, nature seldom forgives errors in judgement, and unlike the Flower Scarab this wasp wasn't so lucky. The Thread-waisted Wasp won't be passing on its genes to the next generation, the Flower Crab Spider might – if it survives the hazards and vicissitudes of an uncertain life – and who knows ... her descendants may still be around in another 300 million years.