B. SCRUB BURROWING WOLF SPIDERS:
The Stay-at-Home Predators

Scrub burrowing wolf spider A spider wasp, after stinging and immobilizing a spider, lays a single egg on the spider's body. When the egg hatches, the larva consumes the spider's soft body parts. Some types of spider wasps attack spiders that spin webs. Other kinds of spider wasps target non-burrowing wolf spiders and can be seen searching along the ground for their prey. Yet another type of spider wasp will dive bomb a scrub burrowing wolf spider tunnel. And although the spider is almost always home, the wasp is not always successful! With practice, you can easily recognize spider wasps at a glance. These long-legged, very active, black insects often have a red band on the abdomen. They spend much of their time running around on the ground, flicking their black wings open and shut. Spider wasps are very active and agile. The female spider wasp provides each of her many young with a single paralyzed spider-which is all the food the larva will get. To make sure the larva grow to be at least her own size, the female spider wasp must battle spiders as big as she is-or even bigger! Bare-sand-loving burrowing wolf spider burrow Leaf-litter-loving burrowing wolf spider burrow

Introduction

Have you ever noticed a perfectly round hole in the ground that looks like someone stuck a pencil straight down into the sand? Most likely, the hole was the burrow of a scrub burrowing wolf spider. If you kept looking, you probably saw a cluster of these small holes.

The burrows of this spider can be found fairly easily throughout the year. But consider yourself lucky if you actually see a scrub burrowing wolf spider! They're very reclusive and leave their excavated homes about as often as a couch potato leaves the sofa---and usually for the same reason. Food! Because the burrows are much easier to find than the creatures that make them, we can learn a lot about scrub burrowing wolf spiders--including their size, age, and species--by carefully observing their burrow entrances.

Look for burrow holes in open sandy patches and in nearby areas scattered with leaf litter. (The sandy patches can be as small as a kitchen table.) In the fall, look even more carefully for tiny holes made by young spiders that no longer live in their mother's burrow. You may find other wolf spiders on your school grounds, but they do not dig burrows in the open sand like the scrub burrowing wolf spider.

You can sometimes catch a quick look at a scrub burrowing wolf spider by gently wiggling a grass stem or pine needle at the edge of its burrow or dropping a few grains of sand over the hole. The spider will often scurry up to the burrow entrance to investigate. These nocturnal invertebrates, whose eyes reflect light, can also be seen at night with the help of a flashlight. Hold the light at your eye level and direct the beam onto the path in front of you. Once you locate a pair of shining eyes, hold the flashlight steady on the spider as you walk up for a closer look. Sometimes the light attracts insects and the spider will hunt in your spotlight!

After completing the activity in this section, your students will, hopefully, understand spiders better and be less susceptible to arachnophobia. The wolf spider is just another interesting and harmless creature preoccupied with making a living in a world filled with natural enemies.

What's the Word on Wolf Spiders?

Wolf spiders hunt rather than build a sticky web to catch prey. They use their silk to line the top of their burrows and prevent cave-ins. Because they are hunters, wolf spiders have excellent vision (they have eight eyes, after all), large jaws, a well-developed sense of touch, and long, strong legs. Scrub burrowing wolf spiders have a slow metabolism and can survive for days without eating. Because scrub burrowing wolf spiders don't venture far from their burrows and prey can be very scarce, this slow metabolism is important! Scrub burrowing wolf spiders conserve energy year round by spending most of their life in the insulated burrow.

Newly hatched male and female spiders stay in their mother's burrow and live on the reserves from their yolk sacks. Once a spider's exoskeleton hardens and it can walk and hunt for itself, the young spider leaves its mother's burrow to build its own tiny home--which the spider will enlarge as its body grows. When ready for a meal, adult females will rush out to pounce on passing prey. Young males venture out at reproductive age in search of females, but die after mating. Scrub burrowing wolf spiders can live for two years, which is longer than the one-year life span of most spiders.

When building a home, scrub burrowing wolf spiders, unlike ants, do not pile sand up at their burrow entrances. Instead, they carry sand out with their mouth parts and distribute the grains evenly nearby. The burrow is simply a vertical tube about 20 cm deep with a small enlargement at the bottom. The enlargement not only gives the spider a place to turn around, but also provides room for the spider to eat prey and, in the case of a female, form her egg sack. The burrow is very narrow, which helps keep predators out. The spider stays in the tube part of the burrow, blocking the tunnel with her head and big jaws, which protect her from predators such as the spider wasp.

Several thousand species of wolf spiders have been discovered worldwide by biologists. The Florida scrub is home to six of these species that are especially well adapted to hot, dry sandy conditions. As the soil temperature changes, scrub burrowing wolf spiders adjust their temperature by moving up or down in the burrow. On a cool morning or during the night, wolf spiders will most likely stay close to the warm surface. In the middle of a hot day, the spider will move deeper in the burrow to stay cool. The humidity in the burrow keeps the spider from drying out.

The six species of scrub burrowing wolf spider that occur in scrub habitat are never found all together on a single ridge (See pages 10-11 for more information about the location of Florida's ridges). Instead, each of the several high ridge systems in Florida is home to only two species. And although both species of scrub burrowing wolf spiders live in scrub, they occupy different microhabitats. One of the species lives in open, bare patches of sand with no overhanging shrubs, while the other species lives in areas covered with leaf litter, closer to shrubs and trees. You rarely find bare-sand-loving burrowing wolf spiders and leaf-litter-loving burrowing wolf spiders in the same place! Both species are extremely sensitive to an obvious difference in microhabitat: the presence or absence of leaf litter on the sand.

The well-camouflaged, bare-sand-loving burrowing wolf spider mixes sand with silk to reinforce its burrow entrance. If conditions have been windy, the silk and sand will sometimes form a slight raised edge, giving the burrow an ant hill appearance. Bare-sand-loving burrowing wolf spiders are picky about their space! If leaf litter suddenly covers an area where a bare-sand-loving spider lives, the spider will abandon its burrow!

The leaf-litter-loving burrowing wolf spider, which tends to be darker in color than the bare-sand-loving burrowing wolf spider, uses its silk to weave a turret (raised collar) of leaves and pine needles around the mouth of its burrow. The turret helps camouflage the burrow entrance and also helps to reinforce it. Leaf-litter-loving burrowing wolf spiders can be found in open lawns as well as in scrub.

Burrows of both scrub burrowing wolf spiders are usually found near their own kind in an aggregation, or cluster. The bare-sand-loving wolf spiders are very particular and have a tough time finding suitable sites. So when a site is good, lots of spiders will live there. Also, breeding is easier for both species if they don't have to travel far to find a mate! What a relief for spiders who like to stay home!