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BY SUSIE FORK

July 2004: A simple way to gain an appreciation of the significance of insects is to view these creatures in context of the entire animal kingdom: 95 percent of all animal species on Earth are insects. More than one million insects have been identified to the species level, and at least ten million more species remain to be identified!

A grasshopper perches on the blossom of a native flower, Farewell-to-spring.

Insects, like many other invertebrates, belong to the phylum Arthropoda, a group that includes such diverse animals as crustaceans, spiders, millipedes, and centipedes. Every arthropod has a segmented body with paired jointed appendages, bilateral symmetry, and a chitinous exoskeleton. Within this phylum are several classes, including the class Insecta, which comprises all of the insects. All insects have two antennae, a body composed of three segments (head, thorax, and abdomen), six jointed legs, and an exoskeleton. The arthropods that are not insects include millipedes, centipedes, arachnids (spiders and ticks), and crustaceans (crabs, shrimp, sow bugs). These other invertebrates differ from insects, for example, by having more body segments or appendages.

We know this California Long-horned Beetle is a male because of its "saw-blade" antennae.

The class Insecta is subdivided into 32 orders, and members of each order share a suite of characteristics. The largest order, in terms of the number of species, is Coleoptera (beetles), which includes 500,000 species. One in four animals on Earth is a beetle, attesting to the prevalence of this group. Other conspicuous orders include Hymenoptera (bees, ants, and wasps), Diptera (flies), and Lepidoptera (butterflies and moths). The highly social termites (order Isoptera) and ants, that form huge colonies, each contribute an astounding 10 percent of the total animal biomass!

Insects make a living in many ways. As herbivores, insects eat more plants than any other animal on Earth. Many are predators and parasites of other insects or of vertebrates (animals with backbones). Insects are also a huge source of prey for other animals. As decomposers and detritivores, insects provide clean-up services by recycling dead plants and animals. Insects are abundant in most habitats, including in terrestrial, freshwater, and brackish water environments and can be found in extreme environments such as hot, dry deserts or well above timberline at high elevation. Interestingly, only a few insects have colonized the marine environment.

A yellowjacket probes the flowers of the native California Coffeeberry.

Elkhorn Slough hosts a diverse assemblage of insects. Brackish pools teem with water boatman and fly larvae, while adult brine flies swarm above the water surface. Cattail Swale is home to a variety of aquatic insects, including dragonfly and damselfly nymphs, as well as many diving beetles. In the upland habitat one might come across the brightly colored, furry velvet ant (actually a wingless wasp) scurrying along the ground in search of her prey, the offspring of a solitary bee. If you’re lucky, you might even glimpse a large black wasp – the tarantula hawk – flying low over open grassy areas in search of its tarantula prey.

The predatory Bumblebee Robber Fly has evolved to look like a bumblebee, perhaps to give its victims (typically, honeybees) a false sense of security, perhaps to escape predation itself.

Insects you are more likely to see here include the spittlebug (nymphs of small, drab insects called "froghoppers") living hidden in the middle of protective globs of foam, and the big black shiny stink beetle lumbering along in open dry areas.

These are just a few of the many insects that await discovery by an observant visitor to the slough. There is definitely more than meets the eye to be discovered here, and the slough will richly reward those willing to stop and take a closer look.