Pirate wolf spiders in retreat

This afternoon I walked to local pond in search of dragonflies. Only Azure damselflies were active, half a dozen males bobbing about searching for females on the pond edge, a pair mating. As I looked for exuviae on the plant leaves, I noticed two female Pirate wolf spiders, possibly Pirata piraticus, in silky retreats at the base of branched burr-reed leaves, both carrying their bright white egg sacs. Apparently, unlike other wolf spiders, they build silky tubes, sometimes partially submerged, from where they hunt passing insects.

Lycosidae: wolf spiders

There are 37 British species belonging to this family. Lycosids or wolf spiders are medium to large species that are usually found running on the ground, although are burrow dwellers and others live near water, and can dive for safety. They are highly visual spiders, and have a pair of large eyes and then two small pairs in a row underneath and two middle sized ones on the side of the head. Most species are active during the day, with a strong tendency to bask in sunny spots in the open, often in large numbers in some species. When resting they fold their front legs underneath their body, and leave the rear legs stretched. When disturbed they can quickly run, even jump, for cover. They can be remarkably camouflaged in their habitats.

Courtship
Wolf Spiders typically mature in the spring. Adult males spend much of their time finding and courting females. They might locate the female first using pheromones, but the courtship display uses mainly visual cues. Male palps or front lets tend to be dark and males will wave them up and down alternatively, vibrating the palps and abdomen in front of females, legs stretched as in tiptoes, approaching a little bit in between signals. Females may accept the male by tapping their front legs rapidly on the ground, however they often retreat, or lunge at the males to scare them off. This rarely deters the insistent male for long. Read this post in BugBlog for more on the courtship of these spiders.

Mature male Pardosa sp. on the look out for females

A male courting an egg carrying female

Egg sacs and spiderling piggy backs
Their wandering nature has resulting on wolf spiders unique way to carry their egg sacs and their young. Females wrap their eggs in lentil shaped egg sacs that they secure to their spinnerets and carry with them for a couple of weeks. The female opens the egg sac to allow the spiderlings to emerge. Once they do, they climb onto their mothers abdomen and are so carried for several days.

Pardosa, likely amentata, a common species in my garden.

This is the bluest eggs sac I've seen on a Pardosa female. Possibly freshly made?

Pardosa female with her spiderlings

A wolf spider gallery

This family, as many other spider families, contains many species that are difficult to identify in the field. If you see any obvious identification mistakes please let me know.

Arctosa perita, an amazingly camouflaged species on sandy beaches and dunes (also top shot). This one photographed at Spurn Point yesterday. This species makes a silk lined burrow where she spends much of her time (read this post from Catherine Scott's blog with fantastic photos of this species and the burrows they make).

Possibly Pardosa pullata, female with egg sac, on rocky mountainside

Female Pardosa possibly amentata with egg sac, basking in the garden.

Unidentified wolf spider with spiderlings on mossy, heathland area.

Trochosa sp. on pond margin.

A Pirata piraticus, pirate wolf spider, resting on the water surface. This spider can be found on ponds and they often run across the surface, where they hunt small invertebrates.

The striking male Pardosa lugubris/saltans

Female Pardosa lugubris/saltans with egg sac

Pirate spider eyespots?

Wolf Pirate Spiders (likely Pirata piraticus, but there is a similar species, P. tenuitarsis) are one of my favourite spiders, their existence in the boundary of water and land, and their ability to walk and run on water makes them fascinating. A few days ago at the wildlife garden, I discovered a curious fact about them while looking at a photo of a female carrying an egg sac. The female was lodged at an angle on some leaves and I did a double take: it gave me the impression that the abdomen of the spider was in fact, its face. This impression was due to two paired white spots on the female's abdomen looking like eyes. Instead of a spider facing away with her egg sac attached to its abdomen, it looked like a spider looking forward, while carrying its egg sac on its jaws, in the way of nursery web spiders. Pirate spider eyespots? Wolf pirate spiders have paired line of white spots on their abdomen, so I wondered if it was just this particular individual that casually had the spots in the shape and area to give this impression. I checked my photos of this spider and found at least two others with the same spots, one also carrying an egg sac. I also found other photos on the web of this species with the same abdominal spots.

Another Pirata sp with egg sac and 'eyespots' 22/07/2014, same habitat

For comparison, a female nursery web spider carrying her egg sac with her chelicerae.

 Only photos taken in a particular angle, of the spider facing away show this, and I guess everybody prefers a front shot of a spider, so I think this pattern is probably found in the species at least regularly, and not only in the females, this side view of the spider allows to see the larger spot towards the end of the line of spots in a male

24/05/2014

A frontal view of the same male showing his enlarge palps:

Have these spots evolved due to them giving an impression of eyes to visual predators, as the eyespots found in some caterpillars and butterflies? In some cases eyespots function to startle a predator giving the impression of a different, larger animal (like the elephant moth caterpillar, the peacock butterfly or this amazing tropical caterpillar), instead, in the wolf pirate spider the eyespots would work like those found at the rear end of some fishes and butterflies, whose function might be to trick or confuse a predator as to where the head of the animal actually is. In fact, eyespots are not unheard of in spiders.

 Why would this be beneficial to this spider? What follows is only speculation, but apparently, wolf pirate spiders live in retreats in moss at the shore of ponds, and females carrying egg sacs often expose the egg sac to the sun at the retreat entrance, while the female remains inside. This could put the female in danger of predation, as she would be less able to detect danger, so the eyespots could afford some protection to the mother and its offspring to be, but I am not aware of any research into the evolution of these eyespots.

With thanks to Catherine Scott (@cataranea) for discussing this on twitter before I wrote the post.

Watching Pirate wolf spiders

I went to the wildlife garden with the intention of watching some wolf pirate spiders. These are spiders that often walk on water and are found in close association to wet habitats. They are wolf spiders and, although they make a silk retreat, they do not make a web for hunting, instead relying on an ambush strategy to capture prey. The species in the pond most resembles Pirata piraticus, the most common species. These spiders are found as adults from May to September.
 I sat by the edge of the pond, and was entertained by several pond skaters squabbling for a dead mirid bug.

But it wasn't long when I spotted a male pirate wolf. I took a photo, but he rapidly disappeared in the thick vegetation of the pond. These spiders have a very characteristic coluration, with a whhite edge around their thorax and abdomen and a background rich brown and greenish, with unpatterned legs. Males have paired white spots on the abdomen, while females also have a white V shaped mark around the middle of her abdomen.

Another smaller individual, also a male, crossed the pond rapidly. In a cursory view they do look remarkably like pond skaters, specially due to the pale fringe of the abdomen and the way they move on the water...

...but he crossed the pond again and I lost it too.

Then I spotted another one. This one looked quite shy and reluctant to move, and it sat hidden by the stems on the water edge.

 I got closer and gently enticed it to come out (top shot and below) and then it become obvious that she was carrying a large, white egg sac.

It then become obvious why the white stripes, these are very similar to the reflections of the water on the edge of the pond, and probably help concealing the spider to their predators, and possibly their victims.

Wolf spiders walking on water

The other day in the wildlife garden, I noticed a wolf spider, Pardosa sp., running on the pond water. I had to look closely as I had never seen them doing this and I wondered if it was a Pirate Wolf spider instead, which also live in the pond and are normally associated to water. But alas, no, it was definitely a common wolf spider like those living in my garden. She confortably moved by the water's edge, often with its front legs resting on the water surface, happily floated on the water on their hydrophobic tiptoes and easily run away very fast on it when came close.
 There is a single species of British truly aquatic spider, which live most of their lives under water, Argyroneta aquatica, the Diving Bell Spider or Aquatic Spider. The two species of Raft spiders, Dolomedes sp., one an endangered species in the UK, are semi-aquatic, and live in marshy places and hunt on water, diving if they feel in danger. Wolf Pirate spiders, Pirata sp. as I mentioned earlier, also associated to water and their protective silk tube built on sphagnum mosses ends by the water surface. All these species are unusual in which they have hydrophobic body surfaces, with short hairs that repel water and in the case of the aquatic spider, form a thin coating of air when the spider dives. Gail Stratton and her colleagues studied the locomotion behaviour or 249 American spiders of a 42 families to understand their evolutionary basis. The researchers placed the different species on water surface and recorded their movements. Some spiders sunk immediately. Other spiders which were able to float sometimes used a specialised gait, called 'rowing' which consists on keeping the first and fourth pairs of legs immobile, and moving the middle two pairs simultaneously as propellers, in a similar way to a pond skater. Some spiders able to float would walk as they would do on land. Stratton and colleagues plotted their result on a phylogenetic tree to understand if hydrophobicity and rowing behaviour have evolved just once or more times. You would naturally think that aquatic spiders have evolved their hydrophobic nature in order to be able to live in, on or near water, but in reality, they belong to a small group of spider families in which most if not all species are naturally hydrophobic, and can run - or row - on water. Two of these families, which are closely related, Pisauridae - the family to which marsh spiders belong - and Lycosidae, the wolf spiders, include many species that, although not normally associated to wet habitats, have no trouble walking on water if they need to. Hydrophobicity seems like a prerequisite for regular association to water and later semiaquatic habits.
 I wanted to check this by myself with the wolf spider living in my garden, which is likely to be Pardosa amentata, and captured an individual to test it. I placed it on a lily pad in our bath pond and it had no hesitation on walking on water and no trouble running away. In fact, it was so fast that I was unable to take a video of it doing it!

Pardosa sp. hunting on the pond of the wildlife garden 

This one is my garden spider demonstrating how its legs rest comfortably on the water surface.

More information
STRATTON, G., SUTER, R., & MILLER, P. (2004). Evolution of water surface locomotion by spiders: a comparative approach Biological Journal of the Linnean Society, 81 (1), 63-78 DOI: 10.1111/j.1095-8312.2004.00269.x

Pirate spider

I spotted this Pirate Wolf spider yesterday, which goes with wonderful latin name of Pirata piraticus on the pond of my local wildlife garden. There are several British species, most of them found in marshy habitats. These spiders are not only able to move easily on the wet vegetation, but they can run, walk and stand on water, as this one shows. They can even submerge, surrounded by a bubble of air, in case of danger.