On most occasions, before I start listing amazing things about wolf spiders (family: Lycosidae), I’m asked: Why are they called wolf spiders? One popular origin story for their scientific name Lycosidae (Lycos means wolf) is that their style of hunting resembles a wolf’s. They are ground-dwellers that chase and hunt their prey. However, unlike wolves, they are solitary creatures that wander across a wide range of habitats.
Wolf spiders in the genus Pardosa, are an excellent example of how well-adapted these hunters are to a range of habitats. For instance, of the 500+ spiders in this genus, the Pardosa glacialis lives in freezing cold arctic regions and is called the Arctic wolf spider; the Pardosa pseudoannulata lives around water bodies and wetlands, and four species of Pardosa are found in highly arid regions such as the Desert National Park, Rajasthan. The Desert National Park, situated in the Thar Desert in the easternmost area of the Sahara-Arabian desert belt, is a sparsely vegetated thorn forest. All the makings of a perfect habitat for this highly adaptive ground-dwelling hunter.
Night stars on the hunt
Looking for wolf spiders at night in arid habitats like these feels like part-arachnology, part-stargazing. You start by looking for eyeshine, flashing your torch on the ground. When you chance upon them, they look like sparkling diamonds dotting the floor. The experience of seeing them shortly before or after the mating cycles is a sight to behold. The densely populated patches play host to a twinkling tapestry of lights, with spider eyes replicating stars.
The sparkle in their eyes is a trait that makes the wolf spider such a formidable nocturnal hunter. To allow for extraordinary low-light vision, the wolf spider has evolved a ‘tapetum lucidum’. This membrane is found in a range of hunters from sharks to cats that may rely on low-light vision to operate successfully at night. The membrane acts like a small mirror that reflects light back into the eye to increase the likelihood of fully leveraging each photon that enters the eye. In the wolf spider, the reflections seen are typically from the posterior median eyes (middle eyes on the upper row).
This pair of eyes along with the posterior lateral eyes (eyes on the sides of the head) are primarily used for long-range endeavours like detecting the presence of a predator or potential prey. When they are close enough, the anterior eyes (the lower row of eyes) also pitch-in to gauge distance and finally aide in capturing their prey. Like most spiders, Lycosidae digest their food externally. This involves injecting their prey with digestive enzymes that softens and dissolves it, and then consuming it like a breakfast smoothie!
Home is where you make it
When they’re not out dazzling the desert floor, wolf spiders are seen back in their retreats that come in a variety of shapes and sizes. While a few wolf spiders build funnel-webs, a vast majority choose to live as ground-dwellers. To escape extreme desert weather and potential predators, many rest under rocks or create burrows.
These burrows serve several purposes from helping the spider thermoregulate through the extreme temperatures in a desert, to being one of the things a female looks for before considering at potential suitor, worthy. In the curious case of Allocosa brasiliensis, a wolf spider from South America, the male builds burrows in sand dunes and then releases pheromones that attract nearby females looking for a mate. When the female finds a potential mate, the subsequent courtship ritual includes a dance duet — the female waves her front legs in the air and the male expresses interest by shaking his body inside his burrow. She then follows him into the burrow to inspect the length of the burrow. Females of this species have been known to mate preferentially with males with long burrows.
This ritual of a female spider looking for a male is an anomaly in the spider world. In almost all spiders including other wolf spiders, it is typically the male that goes in search of a female mate.
Courtship among wolf spiders varies greatly between species. However, they primarily vary within different combinations of visual, chemical and vibratory cues. Some studies have even shown individual variation in courtship behaviour.
Courtship behaviours of the Schizocosa genus are among the most well-studied, and reflective of behaviours displayed by many other wolf spiders as well. Females typically leave pheromone trails for males to find them. Once the male arrives, he uses a combination of waving his front legs and in some cases vibrating the substrate to gain the attention of the female. After seemingly dancing with each other, the two proceed to mate. Spiders have an interesting pair of organs called pedipalps — in most spiders, they look like two miniature legs just below the mouth of the spider. Male spiders generate sperm that they transfer onto a web before picking up the sperm and storing it in their pedipalps. During mating, the male inserts his swollen pedipalps into the genital openings of the female spider.
With the exception of the Allocosa brasiliensis mentioned earlier, the female wolf spider is typically larger than the male of the same species. While there isn’t a very large size difference between the female and male wolf spiders, it is enough to create a very interesting dynamic during their courtship. The male has a good chance of being eaten after mating, and in some cases even before he’s had the chance to mate.
After the mating cycle is complete, the female displays one of the most inspiring stories of parenting in the natural world.
The devoted single mother
It begins with the construction of an egg sac. The mother wolf spider builds a thin web structure on top of which she carefully spins a near-circular sheet of silk parallel to the ground. She then gently begins to deposit her eggs onto this disc-shaped silk cradle. Once all the eggs are on the silk, she goes through a delicate process of folding all the edges to completely cover them. A few more final touches and she has created an egg sac that she will carry with her wherever she goes.
While some other spiders like ‘Nursery Web spiders’ are also known to carry their eggs in an egg sac to keep them safe, it is the care that wolf spiders give to hatchlings that truly set them apart. A short while after the spiderlings hatch, the mother bites and tears the egg sac allowing the newly hatched spiderlings to make their way out.
This is followed by a surreal moment in which more than a hundred hatchlings emerge and climb onto their mother’s back. The devoted mother carries her young on her back wherever she wanders. I’ve even had the pleasure of watching a mother with hatchlings on her back out on a hunt. The spiderlings stay on her back for a few days and in some species up to a few weeks.
What makes the story of this mother even more heartwarming is that if she’s presented with spiderlings from another brood, she will care for them like they are her own.
Spiders aren’t usually a favoured topic and invoke mixed feelings in people, I believe a majority of this comes from misconceptions that are generally prevalent about them. As in the case of the wolf spider, they are highly understudied taxa that have the potential to inspire perspectives in science as well as how we live our daily lives. Spiders have a story to tell, only if we listened.
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