Refuge Notebook

Article
October 14, 2005

Daddy Long-legs of the Home, Garden, and Mountains
By: Matt Bowser

Fall is the time of year when, like them or not, we have to deal with daddy long-legs. As the weather cools, they seem to magically materialize around and in our homes, sometimes in alarming numbers. They can be a nuisance in this way, but whether or not the offending animals should be immediately squished, ignored, or gently transferred back to the garden should be considered.

The name daddy long-legs is sometimes used for crane flies or some long-legged spiders, but here I am referring to the familiar spindly-legged arthropods of the order Opiliones. These are not spiders, but like spiders, mites, and scorpions, they have eight legs and they are arachnids. Spiders and daddy long-legs can easily be distinguished by the shapes of their bodies: the body of a spider is divided into two main parts separated by a narrow constriction; the body of a daddy long-legs appears to be one broadly oval part. Females, especially when full of eggs, are stouter than the smaller-bodied, longer-legged males.

Daddy long-legs have neither fangs nor venom, so they cannot bite people. Instead, they have tiny pincers that they use for grabbing and cutting up their food. These are much too small to be harmful to people, at least in our Alaskan species. Most daddy long-legs are generalist scavengers and predators, eager to eat just about any kind of minute animal. Some also eat small amounts of vegetable matter. Most of them hide by day and prowl about at night. They repel potential predators by exuding foul-smelling, distasteful secretions from their scent glands.

We have at least five kinds of daddy long-legs on the Kenai, each with different habits. The daddy long-legs most often noticed by people is Phalangium opilio . This is the large, mottled gray to brownish variety that is often abundant in gardens, driveways, and yards. They are often active out in the open during the day. Like the cockroach, the house fly, and the silverfish, Phalangium is associated with humans in many parts of the world. It is native to the Old World and is probably introduced in Alaska. It is not a pest, though. In the garden, it is a beneficial animal, eating many small, soft-bodied pests including aphids, caterpillars, grubs, and slugs.

Nelima paessleri is the daddy long-legs that can gather in the thousands in crawl spaces, basements, and well houses. They are mostly burgundy to red-brown with banded legs. Nelima is found in much of the boreal forest, where they live secretive lives until the fall, when they seek out warm, damp nooks to spend the winter. They concentrate in particular places because they are all looking for the same kind of situation. No one knows for sure, though, why they gather into dense clumps that can comprise thousands of individuals. The most likely reason is a principle called amplification, where a signal becomes more potent or “louder” by concentration. In this case, the odor given off by a single Nelima when disturbed may not be especially noticeable and might not deter a hungry predator, but the stench given off by a mass of a thousand upset daddy long-legs could not be ignored and would repel all but the most desperate of predators.

Leiobunum exilipes is also common around houses. It is a small, black, forest-dwelling species.

At the seashore, Leptobunus borealis can be found by day in rock outcrops and under driftwood, stones, and debris. They are small, mottled gray, relatively short-legged daddy long-legs.

We discovered a previously unknown, alpine species of Leptobunus near the Skyline Trail this summer. It is a delicate, dark brown species that lives in cracks of alpine bedrock outcrops by day and walks about out on the faces of the outcrops by night. At this point, we do not know whether it is a rare species that lives only in that particular area or whether it has a broader range and has only been overlooked. We hope to learn about the range and behavior of this species next summer.

The household varieties of daddy long-legs are plentiful, so squishing a few should not harm any population. It is wiser, though, to let them live outside the home and devour pests. A daddy long-legs found in the house may be caught by herding it into a butter dish or simply picking it up, then releasing it in the garden. A mass of Nelima already in the crawl space may be left alone so that they can exit in the spring. Entrance of daddy long-legs into the home is best prevented by a well-sealed structure.

For pictures and an excellent fact sheet about Phalangium opilo as a biocontrol agent, visit the following web page: http://www.nysaes.cornell.edu/ent/biocontrol/predators/phalangium_opilio.html

For a research paper documenting large aggregations of Nelima paessleri and attempting to answer the question of why they aggregate, download the pdf file: http://www.americanarachnology.org/JoA_free/JoA_v12_n2/arac_12_2_0195.pdf

Matt Bowser is a seasonal biological technician at the Kenai National Wildlife Refuge.