Glossary

Arthropods (ár-thruh-pawdz) are invertebrate animals — animals without backbones — with segmented bodies, jointed legs, and external skeletons known as exoskeletons. The group includes insects, spiders, centipedes, millipedes, and crustaceans such as sowbugs and pillbugs — many of which are familiar to anyone who has turned over a rock or lifted a piece of bark in a San Lorenzo Valley garden.

Arthropods are among the most ecologically significant animals on Earth — present in the soil, under leaf litter, on plant stems, and in the canopy above. They pollinate native plants, break down organic matter, cycle nutrients, control pest populations, and form the nutritional base that supports birds, amphibians, and mammals throughout the food web.

Throughout the San Lorenzo Valley — beneath coast redwoods and tanoak, along riparian corridors, and into chaparral and oak woodland edges — sowbugs and pillbugs work alongside millipedes to shred and decompose leaf litter, feeding the soil food web from the bottom up. Centipedes prey on smaller arthropods in the same layer, regulating populations and transferring energy upward through the trophic structure. Above ground, native bees, beetles, and flies move between flowers, while caterpillars — the larval stage of moths and butterflies — convert plant material into the concentrated protein that nesting birds require to raise their young.

Here, a healthy arthropod community is the foundation of a functioning habitat garden. Without them, the trophic web collapses:

• No caterpillars means no nesting birds.
• No decomposers means no soil health.
• No pollinators means no seed set.

Supporting arthropods means:

• Leaving leaf litter in place
• Avoiding pesticides
• Planting the native host plants on which their life cycles depend

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