Life in a pinecone

Life in a pinecone

By Robert A. Hedeen, Naturalist

Have you ever kicked a pinecone as you wandered about in the woods? Do you remember engaging in pinecone battles as a child? If you did, you were, in all probability, disturbing an entire ecological community.

Many believe that pinecones, empty and attached to trees or lying in the litter and duff of the forest floor, have fulfilled their biological purpose of producing seeds for the next generation of pines and have no other function. Such is not the case.

These uniquely shaped structures provide an excellent home for dynamic communities of arthropods (jointed-legged, invertebrate animals)—insects, mites, spiders, centipedes, and millipedes.

When we think of the multitude of arthropods inhabiting the earth, we conjure visions of relatively large animals such as grasshoppers, butterflies, garden spiders, crayfish, and crabs. The truth of the matter is, however, most arthropods are quite small and go unnoticed by all except the most careful observer.

Of all the different animal groups on earth, the arthropods are the most successful if we judge biological success by the number of different species and number of individuals making up the various species. There are more than one million different species of insects presently known to science, and some authorities believe there are another million species still remaining to be discovered and named. This number of known insect species alone is far greater than the number of species recognized for all the other animal groups combined, both vertebrates and invertebrates.

There are many reasons why the arthropods have been such a phenomenal evolutionary success: their tremendous reproductive potential, and some have wings, a hard outer covering of protective armor. Most biologists agree, however, that their generally small size has contributed most to their success story.

Each animal species must have a place to call home, their specific ecological niche. Small species are able to invade and exploit nooks, hollows, crannies, and recesses in the environment that larger types cannot squeeze into. A pinecone offers an ideal place for tiny types to set up housekeeping.

The structure of a pinecone affords sanctuary for arthropod inhabitants and visitors to feed, seek mates, lay eggs, hide from enemies, or simply escape the rigors of everyday life in a hostile environment. Many of the animals found within a pinecone find access by moving up the tree and out on the branches to the cone or by crawling into it when it falls to the ground. Others may fly directly to the cone, and some types may complete their entire life cycle within the cozy confines of the scales of the cone before and after it falls to the ground and eventually decomposes.

The types and numbers of animals occupying a cone vary with the type of pine involved, weather conditions, and competitors for space already present.

Although some pinecone denizens are “large” (up to an inch in length, centipedes for example), most cone residents are quite small and can be studied only with the aid of a microscope or strong hand lens. These smaller ones range in size from about one eighth of an inch or so to about the size of the period at the end of this sentence.

The surprising and exciting diversity of life within a pinecone can be appreciated by simply picking up a few cones and tapping them lightly over a light-colored surface, such as the palm of the hand, handkerchief, or a piece of white paper. A strong hand lens is recommended for studying the smaller forms.

One detailed study of the inhabitants of the cones of the white pine found the following types of arthropods to be present in decreasing order of abundance: barklice, mites, thrips, springtails, spiders, ants, minute wasps, flies, beetles, crickets, wood roaches, so-called true bugs, centipedes, aphids, leafhoppers, scale insects, millipedes.

The next time you encounter a “dead” pinecone, take a minute to remember that its biological usefulness is not at an end as a multitude of animals are utilizing it in a complete system of interrelationships.

To be small and inconspicuous is frequently advantageous to individuals of all species, including man.

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