Wild Side: Wolf spiders

You can find this eight-eyed wonder in a wide range of Island habitats.

A member of the genus Rabidosa photographed in West Tisbury. — Matt Pelikan

“Rage, rage against the dying of the light,” urges the poet Dylan Thomas. The target of his petulance, I expect, was mortality. But as a bug enthusiast, I feel the same way about winter. Short days of cold weather and few arthropods depress me.

Experience, though, has taught me that surprising numbers of cold-blooded critters remain active through the winter months and can be found at the right times and places. And I mean found reliably, not stumbled over as a freakish accident.

For a few of these arthropods, winter is actually at the center of their life cycles. Species like the winter moth and the winter crane fly, for example, are optimized for life in cold weather and hit the peak of their reproductive activity as temperatures skirt freezing. A far more common model is survival into or through the winter in a semi-dormant state, with periods of activity when conditions are moderate. A good example of this strategy comes from the wolf spiders, members of the family Lycosidae.

On Nov. 18, unseasonable warmth sent me into the field to enjoy a gratifying burst of arthropod activity. One delightful find was a plump wolf spider, a member of the genus Rabidosa, that I spotted as it rambled through grass at the Nature Conservancy’s Hoft Farm Preserve.

This was not an instance of marginal survival. The spider was in fine fettle, hitting on all cylinders and cantering through the grass for perhaps 75 feet (not far for me but a fine run if you’re an inch-long spider) before it finally paused and gave me an unobstructed photo opportunity. My records show that it was not an aberration: Wolf spiders are not hard to find here on warm winter days, and they survive the winter in large numbers both as adults and immatures.

Among the largest spiders, with plump bodies and robust legs, wolf spiders are ground-dwelling predators that run down or ambush their prey rather than capturing victims in webs. There are other spiders meeting that general description, but wolf spiders can be recognized by the arrangement of their eight eyes (that’s the standard though not invariable eye count for spiders). The posterior lateral eyes — bio-speak for the outboard, rearmost pair — are large, set well back on the head, and generally easy to see even under field conditions.

Lycosidae is well represented on Martha’s Vineyard. Allan Keith’s invaluable 2008 volume, “Island Life,” lists a dozen species that have been documented here, and the iNaturalist “citizen science” website adds four to six more, depending on how you want to count. There are undoubtedly more awaiting discovery and documentation.
Wolf spiders can be found in a wide range of habitats. One member of the genus Pardosa (or perhaps more than one) lives among cobble on the immediate shoreline, where it (or they) can be astonishingly plentiful. Other “wolfies” turn up on wetland edges, in grassland, or among the leaf litter in oak woodland. At least one species lives in silk-lined tunnels in sandy soil. But by and large, this is a rootless, cursorial family, wandering widely and persistently in search of food.

High summer, to be sure, is peak season for wolf spiders, when adults mate and fertilized females produce silken sacks full of eggs. These remain attached to a female’s spinnerets, and she brings it with her on her travels, looking as if she’s dragging a dull marble. When the eggs hatch, the young spiders gang up on the mother’s back and continue to ride, until a molt or two leaves them large enough to disperse and fend for themselves.
As cold weather sets in, adult males are said to die off, but youngsters and adult females begin producing chemicals in their bodies that lower the freezing point of their body fluids: quite literally, antifreeze. Hiding in crevices or under the leaf litter, insulated from extreme cold, many of these spiders will successfully overwinter, their odds of survival probably increasing if a winter warm spell provides an opportunity to rouse, hunt, and lunch on a springtail or two.

I’ll be there to greet them come spring. While my field work never wholly shuts down, it’s generally around mid-March when a pulse of southern air first sends me bug-hunting in a serious way. Wolf spiders are invariably among the first arthropods I encounter. Some will be immatures, just a few millimeters long. And some will be adults, clearly survivors from the year before. Indeed, sources report that female wolfies may survive for several years.
The adults, if they’re lucky and live until summer, will mate again, and the youngsters will mature through a sequence of additional molts in the spring and early summer and also try to find mates. The cycle repeats — continuity that should cheer up even Dylan Thomas.