Research Projects Using Wolf Spiders
Agonistic Behavior
In many groups where there is the potential for damage from fighting, there is frequently some kind of ritualized behavior that functions to determine contests with a minimum of bodily harm. This may be seen in male-male interactions or in female-female interactions. This ritualized behavior is often called agonistic behavior. In wolf spiders this may take the form of arching or waving the front legs or (in males) of making sounds much as they do in courtship.
How to see agonistic behavior between spiders in the class room.
You are most likely to see agonistic behavior in mature males or mature females (see Part I of this guide for information on determining maturity and sexing spiders). Feed the spiders the day before they are to be used, and then simply introduce one into the cage of another individual. Watch closely for any movements.
Courtship Behavior
These behaviors often include a visual component (for example, waving or arching legs) and often an acoustic component.
The sounds are sometimes audible without amplification (if you listen closely!). If the male has secondary sexual characteristics (for example, bristles or pigment on the front legs) he is very likely to use those legs during courtship.
The courtship behaviors tend to be very stereotyped and not learned. The males will perform a "perfect" courtship without any practice at all. Often the female has specific behaviors as well, although it has never been demonstrated that she can make sounds. For many species, the receptive behavior of the females is a "turn" or a pivot, and a "settle" or a slight lowering of her cephalothorax. If the female shows receptive behavior, the male will orient to her (often after the female's pivot), and slowly approach and mount the female. Typically in wolf spiders the male will be on top of the female, with his ventral surface against her dorsal surface and they will face opposite directions. Other spiders have other positions.
Copulation in spiders.
Spiders are nearly unique in the animal kingdom in that their copulatory behavior has two distinct segments. After the male's final molt, he builds a small web called a sperm web, in which he deposits a small amount of sperm from his abdomen. He then picks up the sperm in the copulatory structure on his palp. The pedipalps hold the sperm until it is transferred to the female during copulation. When the male wolf spider is mounted on the female, (on her dorsal surface), he scrapes the side of her abdomen with his palp. The palp catches on the epigynum and a portion of the palp uncoils into the female's copulatory duct. At some point the sperm is transferred, but no one knows exactly when that is.
In some cases, the male will have multiple insertions with his palp on one side and then switch to the other side and the other palp and again have multiple insertions. Other genera will insert the palp once on one side then switch to the opposite side for a single insertion and switch back again (many times). Many wolf spiders have very long copulations with many many insertions. It is not known why their copulations go for 3-4 or even 8 hours.
How to see courtship and copulation in wolf spiders.
The first step to seeing courtship and copulatory behavior is to make sure you have at least one mature male and one mature female of the same species. See part I of this guide for sexing spiders and for determining maturity. Generally, if you collect spiders from one locality and get both males and females, they are likely to be the same species. Next, it is a good idea to feed both the male and the female one day before they are used in an experiment. Cannibalism can happen at any time, but it is less likely if the spiders have been fed recently.
Put the mature female in a container with a paper liner. I have often used 4 inch culture dishes with a filter paper as a liner, but any container that will hold the female will work. Most wolf spiders cannot climb smooth vertical surfaces, but it is often good to have a top on the dish. Let the female stay on top of the paper overnight. On the next day, you can use the paper by itself or the paper with the female to elicit courtship in the male. To see courtship, place the male on the paper and watch for any movement. I often place the male on the female's paper with the female behind a clear (acetate) barrier to first see if the female will show receptive behavior.
Geographic Distribution and Habitat Preferences.
For many species of wolf spiders, their geographic distribution is only poorly known and their habitats have never been reported. Through the Wolf Spider Project, students have an opportunity to increase what is known about both the range and the habitat of a variety of species.
How to Participate in the Wolf Spider Project
This exercise is geared specifically to classes that choose to participate in the Woodrow Wilson National Fellowship Foundation Wolf Spider Project. To participate, you must agree to try at least one exercise using spiders, and to have the species determination of at least two specimens confirmed. In order to do that, you must first collect a spider or spiders (multiple individuals will be helpful), determine that it is mature and what sex it is, and then to send it to Dr. Gail Stratton, Dept. Of Biology, Rhodes College, 2000 N. Parkway, Memphis, TN 38112. The specimen must have a locality label with it (see Part I of this guide).
The identified specimen will be returned to you and it can then be the start of a voucher collection--a collection that you can then use to compare future specimens.
These specimens will be used by me to build more accurate and up-to-date range maps for as many species as possible. I hope at some point to have the maps available on the WWW.
Biodiversity
The term biodiversity has been used in a large number of different contexts in recent times. Often it refers to the overall diversity on the planet earth. However, it can be used in a local sense as in "what is the biodiversity of a particular area?" Even in the United States, in most areas we have only a poor inventory of what species are actually present and we can rarely say even how many species are present.
The biodiversity of an area can be studied in the short term and in the long term. Long term studies are essential to understand large scale changes from such things as habitat destruction or from climate change. Ongoing class room studies can contribute to our overall knowledge of the biodiversity of an area.
It is possible to determine a good estimate of the number of species of a particular group in an area by doing focused collecting and counting the number of different kinds and numbers of individuals. With spiders, it is possible to do such a study with a class by spending one period with intensive collecting and a second and subsequent periods spent examining the specimens and grouping them. Although formal identification of a large number of species can take a large amount of time and effort, it is possible to sort individuals into categories that look alike ("morpho-species") and call them "species a", "species b", "species c", etc. Given such designations, it then becomes possible say how many species are present in an area at a particular time. The number of species present is called the "species richness". A class could then compare the species richness of same habitat at a different time of the year, or could compare 2 different habitats with respect to species richness.
For another example, a class could collect intensively in two areas, a playground and a woods. Spiders can be returned to the classroom in plastic vials for counting and sorting. Following the counting and sorting, the spiders can be released back into the habitat from which they are found. Comparisons can then be made with respect to number of different species and numbers of individuals.
It is very important to return spiders to exactly the same area from where they were collected!