Thin-legged Wolf Spiders, genus Pardosa

Most people think of wolf spiders as big, hairy monsters just this side of a tarantula in size. A few species are, but the overwhelming majority are mid-size or even downright "compact." Case in point, the most overwhelmingly abundant wolf spiders you are likely to encounter are in the genus Pardosa, the "thin-legged wolf spiders." They are mostly small and medium-sized.

Male Pardosa on a streamside rock, Arizona

Wolf spiders in general are rather easily identified by their eye arrangement. Four small eyes are in the front row, lowermost on the face: the anterior medians (center pair), and anterior laterals (one on each side of the anterior medians). The next row is composed of two enormous eyes, the posterior medians. Last in line is one pair of posterior laterals, usually well back on the carapace from the other sets of eyes.

An example of a woodland Pardosa species, male, Colorado

How does one identify Pardosa in particular? Look at the legs. Pardosa has long spines that are almost perpendicular to the axis of the leg itself. Most all other wolf spiders have shorter spines that are more nearly parallel to the surface of the leg. The hind pair of legs is long, and it is often easier to see the spines on that rear pair.

Very dark Pardosa male from high elevation in Colorado

Thin-legged wolf spiders often exhibit some degree of sexual dimorphism, too. Mature males may have a completely different color pattern from females. Identification of species hinges on microscopic examination of the genitalia. Females have a paired genital opening called an epigynum. Males have highly modified pedipalps they use to deposit sperm into the epigynum, like a key fitting in a lock. The pedipalps of a mature male spider resemble little boxing gloves near his face.

Female Pardosa with egg sac attached to her spinnerets

There are sixty-five (65) species of Pardosa currently recognized in the U.S., and 75 species north of Mexico if you include Canada. They collectively measure 3 to 12 mm or so in body length as adults. The cephalothorax is higher than in most other wolf spiders, and the sides of the face are nearly vertical.

Many wetland Pardosa species resemble this one in Colorado

Thin-legged wolf spiders are perhaps most abundant around water, be it a rocky streambed, or marshy wetland, or beach around a lake. They can also be found in wooded areas, prowling the forest floor, scrambling over logs, or darting among leaf litter. Fields are full of them, too, even the edges of agricultural plots. They also occupy some of the highest elevations of any North American spiders, so look for them in the mountains, too. It is interesting that some species can be found in several different habitats, whereas most spiders are confined to one or two (as are several Pardosa species). In short, it is difficult to not find these spiders.

Another Pardosa on a rock in Arizona

Sources: Bradley, Richard A. 2013. Common Spiders of North America. Berkeley: University of California Press. 271 pp.
Vogel, Beatrice R. 2004. "A Review of the Spider Genera Pardosa and Acantholycosa (Araneae, Lycosidae) of the 48 Contiguous United States," J. Arachnol. 32: 55-108.

Spider Sunday: Dotted Wolf Spider

Large wolf spiders (family Lycosidae) are normally difficult to spot, given their habit of prowling on the ground amid tangles of grasses and other vegetation. Imagine my surprise, then, to find one stretched out on grass stems about three feet off the ground. I recognized it as a normally ground-dwelling member of the genus Rabidosa, and I think I know what it was doing up there.

There are five species in the genus Rabidosa that occur in North America, and I was pretty sure it wasn’t the common “Rabid Wolf Spider,” Rabidosa rabida. It was mature, but not that large, and it lacked the pale spots inside the margin of the dark chocolate stripe down the abdomen. Twisting the grasses for a better picture caused it to reveal its underside, and then I remembered that the underside of the abdomen also has a diagnostic pattern of black spots or blotches.

Once I got home, I discovered the spider was a mature female “Dotted Wolf Spider,” Rabidosa punctulata. This particular individual was found at the edge of an open agricultural field in an otherwise wooded area in the Higbee Beach Wildlife Management Area, Cape May, New Jersey, on October 4, 2012. The species ranges from Massachusetts and southern Michigan, south to northern Florida, southeast Kansas, and eastern Oklahoma and Texas.

Mature female Dotted Wolf Spiders measure an average of 15.2 millimeters in body length, while males are about 12.8 millimeters. Adults, at least females, mature between June and October. Mature males appear in early September, but are thought to mature earlier in the year. The male follows the pheromone-impregnated draglines of females.

Recent research has revealed that males of R. punctulata have two alternative mating strategies. Large specimens in good physical condition simply overpower a potential mate, grappling with her until she submits to copulation. I know, that sounds a lot like rape to me, too! Smaller males, or those in poorer condition, go through full courtship displays that involve leg-waving, and stridulation with the pedipalps that cause rhythmic vibrations picked up by the female being courted (see this website).

Mated females take three or more hours to create an egg sac that they attach to their spinnerets, allowing them to continue a nomadic lifestyle. She probably totes her brood this way for about a month. The spiderlings that emerge then pile atop the female’s abdomen, latching onto knob-tipped hairs where they ride until their next molt (roughly three weeks later, extrapolating from data on R. rabida). I could find no reference to exactly when females carry their egg sacs, but presumably it is in late autumn, the spiderlings overwintering in protected places.

These spiders prey on a variety of insects, including small grasshoppers, but may scavenge dead insects as well. Most references indicate that this species is a nocturnal hunter, and mostly waits in ambush for an insect to wander within pouncing range. They may also run down their prey. Prey is seized with the legs, helped by sticky brushes of hairs on their legs. The spider may loosely wrap its prey in silk to help secure it from falling to the ground if the spider is resting on vegetation.

So, what was my spider doing, up a tree in essence, without prey? Avoiding becoming prey itself is my theory. I also observed a large spider wasp, Anoplius aethiops or A. cleora, scouring the ground for potential wolf spider prey in the vicinity of this spider. I suspect the spider beat a hasty retreat out of reach of the typical search zone for the wasp.

Note: This species was formerly known as Lycosa punctulata, and older references will use that name. It has since been determined that Lycosa is an Old World genus with no species in North America.

Sources: Brady, Allen R. and Kelly S. McKinley. 1994. “Nearctic Species of the Wolf Spider Genus Rabidosa (Araneae: Lycosidae),” J Arachnol 22: 138-160
Eason, Ruth Robinson. 1964. “Maternal Care as Exhibited by Wolf Spiders (Lycosids),” Arkansas Academy of Science Proceedings, vol. 18: 13-19.
Fitch, Henry S. 1963. Spiders of the University of Kansas Natural History Reservation and Rockefeller Experimental Tract. Lawrence: University of Kansas Museum of Natural History, Miscellaneous Publication No. 33. 202 pp.
Howell, W. Mike and Ronald L. Jenkins. 2004. Spiders of the Eastern United States: A Photographic Guide. Boston: Pearson Education. 363 pp.
Moulder, Bennett. 1992. A Guide to the Common Spiders of Illinois. Springfield, IL: Illinois State Museum Popular Science Series, Vol. 10. 125 pp.
Wilgers, Dustin J. 2012. “Courtship signal evolution in Rabidosa Wolf Spiders.”.

Spider Sunday: Beach Wolf Spider

Life is literally a beach for the Beach Wolf Spider, Arctosa littoralis. This member of the family Lycosidae ranges throughout the United States and southern Canada, so obviously not all individuals live by the seaside. However, this spider is partial to sandy habitats such as dunes, stream banks, and blowouts.

The specimen shown here is one I encountered in Massachusetts on Cape Cod National Seashore under cover of darkness on July 25, 2009. It had killed what was probably an already weak worker honeybee. This worked to my advantage because the arachnid was not racing across the sand, outrunning me, my light source, and camera.

Arctosa littoralis is a fair-sized spider, mature males and females measuring 11-15 millimeters in body length. Their sprawling legspan adds to their perceived size. Still, good luck spotting one if it isn’t moving. The camouflage of this species is amazingly effective. Mottled gray, brown, or nearly white, it blends in with the sandy substrate upon which it hunts.

It may help to look for them at night. Arm yourself with a good headlamp or flashlight, held at the same level as your eyes. When the beam of light hits a wolf spider, the animal’s eyes will glint with a bluish-green shine. This technique works on other wolf spiders, too, and a female with young on her back looks like a diamond-studded stone. You will be surprised at just how populous lycosids are if you ever try this. I tried it on a lawn in south Texas once. I thought the grass was covered in dew. No, just wolf spiders!

Should you opt to seek the Beach Wolf Spider by day, try turning over driftwood and other debris on the shore. The spiders hide in such situations by day; they may also dig burrows in the sand, so look for that as well.

Despite being a swift, muscular hunter with excellent vision, Arctosa littoralis is not immune from its own predators. Several species of spider wasps in the family Pompilidae are recorded as using the Beach Wolf Spider as food for their larval offspring. Priocnemis cornica, Ageniella conflicta, and Anoplius apiculatus are among the pompilids that prey on Arctosa littoralis.

Summer is here, and vacation time is upon us. Consider looking for the Beach Wolf Spider and other seashore invertebrates during your next leisure trip to the beach. Don’t forget to pack your sunscreen and shades, though.

Spider Sunday: Mother Wolf Spider

Last Sunday was Mothers’ Day, but if you will forgive me I would like to pay tribute to arachnid mothers today. During my trip to South Carolina in early May, I had the occasion to momentarily observe a large female wolf spider of the genus Hogna on the afternoon of May 6, 2012. She had an egg sac and was living in a burrow on a wooded embankment adjacent to a road. I had stopped along with members of the Dragonfly Society of the Americas to look around a stream for dragonflies and damselflies. Descending the steep slope to get to the watercourse, another member of the party spotted the spider.

The arachnid was out of her burrow and standing on a network of threads just outside its entrance. The footfalls of others caused her to dash back into her refuge and I thought I’d seen the last of her.

I waited patiently next to her lair and was surprised when she returned to the lip of the burrow shortly. I was hoping she would climb back out for more photo opportunities, but instead she did something remarkable. She turned around inside her burrow and backed out to the entrance.

Why would a large wolf spider, with quite excellent vision, and perfectly capable of defending herself with her fangs, choose to present her vulnerable abdomen, and the egg cocoon attached to it, to potential lurking enemies? The only logical explanation that came to mind was that she was sunning her egg sac.

Indeed, there was filtered sunlight streaming through the forest canopy in the late afternoon: not too intense as to cook the ova within her silken package, but warm enough to help incubate the eggs. Still, had she not repeated this behavior, turning around at one point to make sure no threat was present and then backing out again, I’m not sure I would have believed what I was seeing.

It turns out this kind of behavior is not unheard of in other wolf spiders. Studies of Pardosa wolf spiders of two species revealed that at least one of them seeks open areas in which to expose the egg sacs to the sun (Buddle, 2000).

Had I been able to return to the site day in and day out, I would have eventually witnessed the mother spider cracking open her egg sac, allowing the newly-hatched spiderlings to emerge. Wolf spider babies crawl from the egg sac onto their mother’s back, completely covering her abdomen and sometimes much of her cephalothorax as well. She will transport the youngsters until their next molt, after which they disperse to live freely on their own.

Such devoted parental care is considered uncommon among spiders, but the more we learn the more the picture changes. There are even some female spiders that die immediately after their spiderlings hatch, offering their bodies as their offspring’s first meal.

A piece of long-standing advice is to “stop and smell the roses,” but it also pays to stop and observe animals, too. Science knows very little of the lives of most organisms that are not economically important, be they food sources or pests. Who knows what could come from your own casual observations of the insects, spiders, and other wildlife that share your yard, garden, and neighborhood park?

Source: Buddle, Christopher M. 2000. “Life History of Pardosa moesta and Pardosa mackenziana (Araneae, Lycosidae) in Central Alberta,” The Journal of Arachnology 28: 319-328.

Spider Sunday: Funnel-web Wolf Spiders

Just when you think you understand spiders, nature throws a wrench in the works to contradict the stereotypes. Wolf spiders in the family Lycosidae are supposed to be nomadic hunters, some of which live in burrows. Not so fast! Believe it or not, one genus, Sosippus, actually spins webs. I know!

If you live in the southern U.S., Mexico, or Central America, you cannot assume that all the thick, sheet-like webs with funnel-like retreats are made by the true funnelweb weavers of the family Agelenidae. Sosippus creates nearly identical snares, sprawling over cacti, agave, and palmetto, or sprouting from rock crevices.

The two spiders also bear a close superficial resemblance to each other. The key to distinguishing them is to look at the eye arrangement. Despite being web-builders, Sosippus shares the eye pattern typical of its hunting cousins: The two posterior median eyes are large and forward-facing, underscored by a row of four much smaller eyes. Two more eyes, the posterior laterals, flank the others. Agelenids have a more compact eye arrangement, with eyes of relatively equal size.

Six species of Sosippus occur in the U.S. The one shown here is S. californicus, which ranges from southern California to Arizona and south through Mexico to Costa Rica. I found it to be very common throughout southern Arizona. They are sizable spiders. Mature females measure from 14.7-17.6 mm (average 16.6) in body length, while males are 13.4-14.4 mm. The species is most abundant in riparian situations, living at the edges of stream corridors or wetland habitats.

One of the behavioral traits that Sosippus shares with other lycosids is the “portable egg sac.” Females tether their egg sac to their spinnerets until the spiderlings hatch. Spiderlings ride on their mother’s back until their next molt, then share her web, sometimes for months. In captivity, older spiders seem capable of coexisting in a confined space provided they are fed regularly. Maternal females of the species Sosippus floridanus have been observed feeding their spiderlings for several months (Brach, 1976). S. texanus is a recorded host for the mantisfly Mantispa sayi, which means the spider’s eggs are consumed by the larval mantispid (Rice and Peck, 1991)

Next time you visit the Sonoran Desert, or the forest hammocks in Florida, keep a lookout for funnel-web wolf spiders. You are sure to find these arachnids to be fascinating residents of these ecosystems.

Sources: Brach, Vincent. 1976. “Subsocial behavior in the funnel-web wolf spider Sosippus floridanus (Araneae: Lycosidae),” Fla Entomol 59(3): 225-229.
Brady, Allen R. 2007. “Sosippus revisited: Review of a web-building wolf spider genus from the Americas (Araneae: Lycosidae),” J. Arachnology 35: 54-83.
Rice, Marlin E. and William B. Peck. 1991. “Mantispa sayi (Neuroptera: Mantispidae) Parasitism on Spiders (Araneae) in Texas, with Observations on Oviposition and Larval Survivorship,” Ann. Entomol. Soc. Am. 84(1): 52-57.

Spider Sunday: Wolf Spider

While living in Massachusetts in 2009 I had the pleasure of prowling around some very nice natural areas with Lynn Harper, an accomplished naturalist who works for the Natural Heritage and Endangered Species Program in the Massachusetts Division of Fisheries and Wildlife. Among the places I went with Lynn was Tully Lake in Royalston. There I was to encounter a very large wolf spider in a wet meadow near the lake.

Scientists have not made it a priority to assign common (English) names to individual species of insects and spiders, unless the creature is of economic significance. Consequently, there is no specific name for this magnificent, eye-catching arachnid. It is probably the species Hogna helluo, though without a thorough physical exam of the specimen it is nearly impossible to be certain. Spiders darken with age, and there is plenty of variability in color and pattern from individual to individual anyway.

Wolf spiders comprise the family Lycosidae, and most of the large North American species belong to the genus Hogna. They used to be classified in the genus Lycosa, but a revision of that genus resulted in the finding that there are no New World species in the genus Lycosa. North American species were thus reassigned to Hogna.

Arachnologists measure spiders by body length, not legspan, but even by that standard, Hogna are real giants. Mature males of H. helluo range from 10-12 mm, while females are a whopping 18-21 mm. Add the sprawling legs and they are an intimidating creature to those unfamiliar with their skittish nature.

Wolf spiders in general hunt “on foot” instead of building webs to snare their prey. Consequently they are more muscular than the average arachnid, with keen eyesight. They are most active at night, perhaps because their arch enemies the spider wasps (family Pompilidae) hunt during the day. Try hunting for wolf spiders yourself, at night. Shine a flashlight or a headlamp over a field, or even a lawn, and you will see the eyes of wolf spiders sparkling like diamonds as they reflect the beam of your light.

Wolf spiders can simply overpower their prey, and if you witness one attacking a cricket or other insect you will probably be shocked by the violence. Still, a wolf spider is going to flee at top speed from your approach. I was fortunate to reel off a number of pictures before this female fled among the grass and moss.

There are many stories to tell about wolf spiders, so I will give away no more secrets today. I will simply encourage you to go out and look for them yourself; and ask that you treat the odd wolf spider that enters your home with a little respect. Please relocate such spiders back outdoors where they can intercept invading insects that could do you, your family and pets real harm. Thank you.