A Little Bit More
Fishing spiders (often called Dock Spiders) are large enough to startle most people when first seen. These large, active spiders are fairly common across North America in watery habitats so you’re likely to see one if you’re in the right habitat. Anywhere people participate in water activities, they’re likely to see one of these spiders. There are about 11 species of fishing spiders north of Mexico and they all look rather similar. Although large and scary, this spider does not pose any threat to humans or pets so you have nothing to fear from these animals.
Fishing spiders are opportunistic predators and usually sit quietly at some location and then ambush suitable prey that passes by but may also hunt down prey items. One species preys mostly on water striders but all will take most anything small enough to subdue.
In general, spiders that make webs and use them for catching food, do not see well but are very attuned to vibrations that prey makes on their webs. Fishing spiders do not make a web for catching prey but at least one kind of fishing spider in Africa, rests its feet on the water’s surface and feels for vibrations from potential prey. Whether this technique is used for North American fishing spiders is not clear – I couldn’t find any reference to this behavior in the literature.
Activities
Science – Spider Hunt
Objectives: Find, identify, and study spider skins (exoskeletons)
Materials: Empty letter envelope
If your home is like mine, no matter how clean, there are corners and out-of-the-way places that have spider webs from time to time. We’ve already noted that fishing spiders do not have webs but they do have an exoskeleton that must be shed periodically for growth to be possible. Spiders, just like insects and crayfish, must molt their outer skin from time to time. Before the old skin is shed, a new one forms beneath and then a fluid, called the molting fluid, is secreted by special glands to loosen the old skin. Once loosened, the old skin splits, the spider works its body out, then removes each of its eight legs. Once the old skin is shed, the new, pliable skin stretches to accommodate an increase in size before it too, hardens.
Have your students go home, or maybe even check out the school area, for any spider webs in their house. Basements are especially good places to look or any room or out-of-the-way places that don’t get a lot of traffic. If they are able to find a spider web, have them look closely for what will appear to be “dead” spiders hanging in the web – these are the shed spider skins we’ve discussed. Not every web has them but often these shed skins remain in webs for some time.
Students can gently remove the web with a stick – don’t touch the spider’s skin or it will crumble – and place the web/skin in an empty envelope. Have them bring in their skin to class so all can see. Granted, not everyone will be able to find a spider skin in their home but out of a normal classroom, there should be enough students who do, so everyone can get a good look. If you have a dissecting scope or magnifying glass/hand lens, these will also make viewing much more interesting.
Key Concepts
Predator/Prey Relationships, Identification, Food Webs /Food Pyramids, Behavior and Regulation, Adaptations and Diversity
Questions
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