Arthro = Joint

Poda = Foot Appendage




     Have exoskeleton which is molted several times during their lives.
Beneath, a new soft skeleton forms, eventually hardening after the old exoskeleton is shed.

     Jointed legs, three pairs in insects.

     Body divided into two or three parts: head, thorax and abdomen.

     One pair of antennae, no antennae in Arachnids, two pair in Crustacea.

     Many groups undergo metamorphosis.




Complete Metamorphosis

            1. Egg

            2. Larva  (caterpillar in moths and butterflies)

            3. Pupa (transition stage)

            4. Adult butterflies, moths, flies, beetles, ants, wasps and bees.                    


Incomplete Metamorphosis

            1. Immature nymph hatches from egg.

            2. Grows, develops wings and by stages becomes an adult. Dragonflies,
               damselflies, grasshoppers, true bugs, cicadas.


Simple Pattern

            1. Newly hatched insect resembles adult.

            2. Grows, molts till reaches adult size.

Silverfish, springtails, spiders (Arachnids) also follow simple pattern development.


                               Insects (Class Insecta)


                           Spiders (Class Arachnida)


                             CLASS INSECTA

                             ORDER ODONATA


Dragonflies and Damselflies

Also called Darning Needles


About 400 species occur in North America. Dragonflies are larger and rest with wings
extended to the sides horizontally. Damselflies are smaller, more delicate, and rest with
wings held to the rear vertically.


Both have large compound eyes. In dragon flies the eyes nearly cover the head.
In damselflies the eyes bulge to the side.


Their four powerful wings move independently, enabling them to fly forward and
backward. Their long legs are used to hold insects captured in flight.


Both mate in flight. The eggs are deposited in water or onto plants in or near water.
The nymphs are predators that capture insects, tadpoles, even small fish. When fully
grown the nymph crawls out of water, splits the outer skin lengthwise on the upper surface
and the adult emerges.







Order name means “straight wing” referring to the forewings. Hind wings are broad and
membranous and are folded flat, hidden under the forewings.


Metamorphosis is incomplete, with nymphs resembling the adults except they gradually attain wings.


Males are known for the musical sounds made when they rub together roughened portions
of their wings or legs. This “music” serves as a form of warning, a way to establish territory,
or a move in courtship.


The order includes 1,000 species in North America and over 23,000 species worldwide.

Jerusalem Cricket/Potato Bug (Stenopelmatus fuscus)

A humpbacked cricket up to 2" in length and wingless. Their threadlike antennae are as long
as their bodies or longer. The head is large with a wide space between small compound eyes and jaws.


They feed on other insects, plant roots, decaying vegetation and potato tubers. Active both day and
night, these crickets often leave distinctive smooth tracks on dusty roads by dragging their bulky abdomens.


Adults are very slow-moving, particularly during mating season. The female often devours her mate.
Females prepare a depression in the soil for masses of oval white eggs.  They usually produce
one generation a year.

                                      ORDER HOMOPTERA


Spittlebugs (Froghoppers)

Called froghoppers because adults are shaped rather like tiny frogs.


Female spittlebugs make a froth on plant stems and grasses to cover their eggs. The young nymphs
make a froth also to cover themselves while feeding on plant juices. Adult froghoppers hop from plant
to plant and seldom fly.


                                    ORDER COLEOPTERA


Ladybug Beetles

During the Middle Ages, these beetles rid grapevines of insect pests and, in appreciation, were dedicated to
“Our Lady”, hence the common name. We have over 350 species in this country, though the family is


Most ladybugs have round, shiny red, orange or yellow bodies spotted with black. Both adults and
larvae are predators, mostly of aphids.


The female may lay up to 500 eggs during a lifespan of a few months. Larvae feed, then pupate.
They produce many generations a year if food supply is good.


Huge swarms of ladybugs fly into canyons. They overwinter on leaves and plants and
return to valleys in spring.




Acorn Weevil (Curculio spp.)

A small beetle with mouthparts modified into a downward-curving beak or snout. Females bore
into acorns, seeds and stems to lay eggs. They often seal the openings with fecal pellets that look
like white dots on the outside of dry acorns.


Larvae feed and pupate inside. One acorn weevil larva can completely consume a small scrub oak acorn.


While it lives, the acorn protects the weevil larvae from most predators, shelters them from weather,
and keeps them moist, cool, and away from sunlight. It also provides a diet rich in fats and carbohydrates.


Adult weevils are active from June through August producing one generation a year, corresponding to
the acorn crop.


Beetles occupy the largest order in the animal kingdom, containing a third of all known insects- 300,000
species worldwide and about 30,000 species in North America.



                       ORDER LEPIDOPTERA


Butterflies have 4 wings covered with scales. They are usually very colorful. They attract mates
by color. They fly only during the day. Butterflies have an enlarged club at the end of each antenna.
At rest, butterflies usually hold wings together vertically over the body.



Moths have 4 wings covered with scales. Most have somber colors and fly at night. Moths emit
chemicals to attract mates. Moths have threadlike or feathery antennae, no clubs on the ends.
At rest, moths fold wings over the body, curled around the body, or flat against a support.





Monarch (Danaus plexippus) 

Our best known butterfly with orange and black wings. A long

distance migrator; west in winter to coastal California, and east in spring to the Great Basin.
Monarchs feed on milkweed. Their disagreeable flavor, caused by their diet, makes birds avoid them.



Lorquin’s Admiral (Limenitis lorquini)

Orange tip on forewings and a white band on both wings. Frequents stream courses
and moist meadows. Flies from May until fall. Feeds on willow, cottonwood, poplar and
sometimes orchard trees.


Pale Swallowtail (Papilio eurymedon)

A butterfly of hills and canyons. Overall pale yellow with black stripes and black tail-like projections
from the hind wings. Swallowtails are attracted to water as well as flowers. Caterpillars feed on
coffee berry and ceanothus.





California Sister (Limenitis bredowii callfornica)

Similar to Lorquin’s Admiral but has blue lines on undersides of wings. Frequents upper
branches of live oaks, on which the larvae feed. The butterfly rarely sips nectar from flowers
but is often attracted to water.






Painted Lady (Cynthia cardui)

Is said to be the most widely distributed butterfly in the world. Forewings above are orange
marbled with black, with white bars near the wing tips. Sometimes found in great migrations
flying a few feet above the ground. Such flights may last for days. Feeds on thistles, nettles,
mallows and many other plants.



Buckeye Butterfly (Junonia coenia)

Light brown color with large multicolored spots on both the hind and forewing.
Caterpillar feeds on snapdragon, monkey flowers, plantain and other herbs.



Edith’s Checkerspot (Euphydryas editha bayensis)  Colors vary from black heavily “checkered”
with yellow or orange. Food plants are usually members of the Figwort family; Bee Plant, Monkey
Flower, Indian Paint Brush, and others. Listed as threatened on the US Endangered Species list.


California Hairstreak (Satyrium californicum) Hairstreaks are small butterflies; most have hair like
tails on the hind wings. California Hairstreak is olive brown above with orange and blue spots at base of “tail”.
Larva feed on oaks and ceanothus.





Tent Caterpillar Moths  (Malacosoma constrictum)

Moths are heavy-bodied, hairy and dull-brown. Adults do not feed and have a very small proboscis
or none at all. Males’ antennae have two feathery branches on each segment. Caterpillars live
together in silken tents, often on oak trees and ceanothus shrubs on which they feed.



                                            ORDER DIPTERA



Flies are easily distinguished from other insects because they have only one pair of normal wings.
Most flies have large compound eyes and mouthparts that are modified for piercing, lapping, or sucking fluids.


Flies exhibit complete metamorphosis. The larvae are called maggots and live in soil, decaying material
or as parasites of vertebrates, snails and other insects.


Valley Black Gnat (Leptoconops carteri)

The most bothersome species, a tiny black fly that torments both animals and humans as it
buzzes in our noses and eyes in the summer looking for sweat secretions. They also occasionally bite us.



Mosquitoes are slender, delicate flies with mouthparts modified into a long tubular proboscis
adapted for piercing and sucking. Nearly all of the females suck blood but the males feed only
upon plant juices, if at all.


Most females need a lot of protein in order to lay eggs. They obtain this protein from the
blood of reptiles, birds, or mammals, transmitting malaria, encephalitis and other diseases
in the process. Eggs are laid on the water’s surface, either in clumps or singly. Habitat
choices for laying eggs range from tree holes, rain-filled footprints, cans, old tires or in
permanent fresh and even brackish water.

The larvae are called wrigglers and most species have a tail respiratory tube which is
projected through the surface film to obtain oxygen. Wrigglers feed on algae and bits
of organic debris. A few species are predaceous and feed on other mosquito larvae.


The larvae pupate and the adults soon emerge from the floating pupae. Adults mate soon
after emergence, and soon after that, the males die. More than several generations a year may be produced.





Honey Bee (Apis mellifera)

These bees are not native to North America, brought here in the mid 1600’s. Flowers are sipped
drop by drop and nectar is carried in bee’s crop (throat pouch) to be eaten immediately by colony or
mixed with saliva and changed to honey for storage.


Pollen is collected on bee’s body hairs and then brushed into “pollen baskets” on its legs. Like nectar,
the high protein pollen can be eaten immediately or stored in wax cells. Humans benefit greatly from bees’
pollination of many flowering plants.



Ants live in colonies with a complex social structure, in underground tunnels or in dead wood. 
An ant family has its own distinct odor. As an ant crawls along he leaves behind (formic acid)
his family odor. Each ant finds his way back to the family by following this secretion. In some
colonies winged males and females emerge from the nest and mate.  After mating, the males die
and the females lose their wings and return to the ground to start a new colony. When disturbed,
most ants are capable of biting or stinging people.


Ant species


     Little Black Ant (Monomorium minimum) 0.1"


     Introduced Argentine Ant 0.1"


     Carpenter Ant (Camponotus spp.)

      Largest of our species, 0.5"









Yellow Jackets (Vespula spp.)

Yellow Jackets are short, stocky wasps, boldly marked with black and yellow banded
abdomens. These wasps make nests of “paper” that they make by chewing bits of wood
or leaves. Most yellow jackets nest in the ground.


Like other social insects, these wasps have a “caste” system made up of queens, males,
and sterile female workers.


The larvae are reared in the cells of the nest and are fed pre-chewed insects and other
“meat” by adults. Adults eat only nectar.


When cold weather begins, all die except mated females, which over-winter among
litter and in the soil. They begin new colonies by them-selves the following spring.


Females can sting repeatedly at the least provocation.










Gall Producing Insects

Cynipid wasps are by far the most common groups of gall insects in California.


The chemical stimulus leading to gall formation may originate when a female gall insect
stings a leaf, stem, or branch and injects a fluid rich in nucleic acids and protein along with its eggs.


The reaction of the plant to the invading organism is one of defense. Gall plant tissue normally
swells outwardly from the area of the egg insertion. This growth usually leaves a chamber or cavity,
which becomes the feeding territory of the larvae. Adult wasps chew their way out of the galls and
drop to the ground. Many gall inducers emerge in spring, timed with the development of new shoots and leaves.


The life cycles of most cynipid wasps and gall sawflies are complicated and have yet to be completely
worked out.









Some Gall Inducers


Live Oak Gallfly (Callirhytis pomiformis)


California Oak Gall Wasp (Andricus californicus) Induces “Oak Apples”


Willow Apple Gall Sawfly (Pontania pacifica)


Coyote Brush Gall Midge (Rhopalomyia californica) (Order Diptera)







 (True Bugs)



     The fore wings fold flat over the back. They are usually leathery at the base and membranous
at the tip and overlap each other.


     The hind wings, which are the flying wings, are uniformly membranous and slightly
shorter than the fore wings


     True Bugs have sucking mouthparts in the form of a beak.








Water Boatmen (Corixa Spp.)

Slender true bugs with long hind legs flattened for swimming. Air taken at the surface usually
surrounds the insect in a silvery envelope. Water Boatmen must hold on to some object in order
to remain submerged. Adults are strong fliers and commonly attracted to lights. They feed on
algae and decaying plant and animal matter sucked from the pond bottom. Oval eggs are cemented
to underwater supports. They hatch in 7-15 days. Nymphs resemble adults except that they may change

color several times and are wingless. In Mexico people eat one

Water Boatmen species in all of its life stages.


Water Strider (Gerris remigis)

Slender, dark, long-legged true bug that skates or jumps about on

the surface film of water. Mostly wingless. They feed on aquatic insects including mosquito larvae that rise to the surface, and terrestrial insects that drop into water.


Cylindrical eggs are laid in parallel rows on an object at water’s edge. Nymphs mature in about 5 weeks. Adults live many months and sometimes over winter under fallen leaves on land near water.


Sometimes called “Jesus Bugs” because they “walk” on the water.

                                  CLASS ARACHNIDA






     Have two body parts, head fused with chest, and abdomen. 

     Four pairs of jointed legs.

     No antennae

     Usually 8 simple eyes in different arrangements.

     Book lungs.

     Pedipalps located between the jaws and first legs. Used by male

      spiders to transfer sperm to female during mating.


Turret Spider (Atypoides riversi)

Turret Spider is in the family of Folding Trapdoor Spiders. Builds silk-lined burrow in soil
and elongates the lining up into a turret-like opening, often camouflaged with leaves and
lichen. Nocturnal, when foraging for food it folds the ends of the turret together, closing it temporarily.


Orb Weavers

Most orb weavers spin spiraling orb webs on support lines that radiate outward from the center.
Many orb weavers replace the entire web each night with a new one, spun in complete darkness
by touch alone.



Black & Yellow Argiope (A. aurantia)

Web usually has crossed zigzag bands which makes for a stronger web, protective against
spider color. Spider hides behind it, birds can see it well so don’t fly through it.


Female fills egg sac, attaches it to one side of web close to her resting position, and then dies.
Eggs hatch in autumn, over winter in sac, disperse in spring. Seems to prefer sunny sites with l
ittle or no wind.




Crab Spider (Misumena vatia)

These small, crablike spiders live in bark or trees or under rocks on the ground. Most are well
camouflaged. Female guards her eggs in a silken cocoon attached to plants but she usually dies
before spiderlings emerge.


Funnel Web Weavers (Agelenopsis spp.)

These spiders spin sheet webs of nonsticky silk. There is a funnel extending off from
the center to one edge, where the spider hides. There is a 3" barrier web over the top.
When a flying insect hits this barrier, it falls into sheet below. The spider rushes out
of funnel, bites its insect prey, drags it back to the funnel and feeds.




Jumping Spiders

These spiders have sharpest vision of all spiders, and are excellent hunters. 
As they leap on a victim, silk comes out from the spinnerets, creating a long silken dragline.
They do not spin webs, but make little silken shelters under bark, stones, or leaves.





Wolf Spiders

They run on the ground or over stones and sometimes up plants. They do not spin webs.
Spiderlings are carried on the females back until ready to disperse.



California Black-eyed Tick  (Ixodes pacificus)

Ticks feed on the blood of mammals. The female, engorged with blood, lays a large
number of eggs on the ground and dies.


The eggs hatch in a few days in warm weather. Hatchlings climb up plants and
latch on to a passing host. They drop off after a meal, molt, and climb to another
host, repeating the process until full grown.



               OTHER ARTHROPODS


                       CLASS CRUSTACEA

                ORDER ISOPODA



Sowbugs are neither bugs nor insects. They are harmless land crustaceans, related to aquatic
animals such as shrimp, crabs, and crayfish. Sowbugs breathe with gills and cannot live long
without high humidity.


These small, flattened, jointed animals live in and under rotting logs, under stones or in the soil.
At night, these animals leave their crevices to forage for food consisting of plants and tiny
animals. As a defense, some of these animals are able to roll up into a ball and are known as “pillbugs”.



                       CLASS DIPLOPODA


Millipedes (Narceus americanus)

Millipedes are slow moving wormlike animals found in damp, dark places, beneath rocks, wood,
and leaves or in soil. Usually blackish in color and many-legged with 2 pairs of short legs on
most body segments. Feed on plants or decaying material. Etc.


Many species are able to emit a foul-smelling fluid through openings along sides of the body. The
substance discourages predators and is poisonous to some creatures.





Centipedes (Scuitgera coleoptrata)

Centipedes are wormlike predaceous animals  found in nearly all land habitats including houses;
under litter bark and rocks during the day. Legs arranged 1 pair per body segment. Feed on
insects and other small arthropods. Centipedes are able to deliver a painful sting from poison-bearing
claws on the first pair of legs.








Found worldwide except in the driest and coldest parts of the world. Their simple design consists
of two tubes- the body and the gut- separated by a fluid-filled cavity. They eat their way through
the soil, depositing piles of “worm castings” on the surface of the ground near their burrows.
Decaying matter is digested and redistributed, and the soil is mixed and loosened, carrying air
and moisture to plant roots and other soil creatures. It’s estimated earthworms have increased
soil productivity as much as 80%.


Earthworms are even able to live in fresh water provided there is enough oxygen. Two
halves of a broken worm can regenerate and live providing large enough pieces exist.



              PHYLUM MOLLUSCA


                      CLASS GASTROPODA


Banana Slug (Ariolimax spp).

Slugs and snails belong to the group called gastropod, meaning “belly foot”. Slugs are land snails
that have no shell. Slugs make a slimy substance that help them move along. Slugs’ slime is so
protective that the slug can climb over a very sharp knife unharmed.


Banana slugs are butter yellow color, and have two sets of tentacles on the head. The upper,
longer pair are the eyes and can move independently. The lower, shorter tentacles are for feeling and smelling.


Inside the mouth is a toothed tongue called a radula. This radula allows the slug to rasp food
into pulp and pull the food into the esophagus. Banana slugs are champion decomposers and
eat living and decaying vegetation; roots, fruit, seeds, bulbs, lichen, algae, fungi, poison oak,
animal droppings, and carcasses.


Banana slugs are hermaphrodites. Each animal has both male and female reproductive organs.
They mate at all times of the year. After penetration they exchange sperm, each producing eggs
and sperm simultaneously. They often become stuck and cannot separate, so they take turns gnawing
off the stuck organ or organs. The severed male organ possibly regenerates.


Slugs deposit a clutch of 30 or more eggs in a hole or crevice where ground water and humidity are high.
Three to eight weeks later the eggs hatch and the tiny slugs are on their own.


Banana slugs must live in a moist environment and can take up water through the skin so do not
need to drink water. They actually enhance with their deposits of nitrogen-rich fertilizer in the
redwood forest. They help ensure the survival of the trees that, in turn, give them moisture and
protection from the drying sun.


Many animals find slimy creatures distasteful. However, banana slugs have many predators,
including garter snakes, foxes, moles, porcupines, beetles, pacific giant salamander, ducks,
crows, millipedes, California newt, and raccoons often skin them before eating.


Species of Banana Slugs

            Ariolimax californicus

            A.californicus brachyphallus (short penis)                              A.dolichophallus (long penis)




























Abdomen - The hindmost part of an insect’s body.


Antenna - One of a pair of sensory organs on the head of an insect, also called “feelers”.
Primarily organs of smell and taste. (Pl. antennae)


Exoskeleton - A supporting structure on the outside of the body, enclosing all living cells.


Larva - Immature, wingless feeding stage between egg and pupa. (Pl. larvae)


Metamorphosis - The transformation of an immature to a mature insect following the feeding
(nymphal and larval) stages.


Molt - The shedding of the confining outer layer of the body (exoskeleton) to permit growth or
metamorphic change.


Nymph - A young insect that resembles an adult, wings develop externally as pads, lives on land
and does not have a pupa stage.


Pedipalps - Second pair of appendages in arachnids. Usually leg-like in female spiders but enlarged
at the tip in males and used as a special organ for transferring sperm.


Proboscis - A prolonged set of mouthparts adapted for reaching into or piercing a food source.



Pupa - The transitional stage of insects during which the larva changes into the adult form completing its


Spinneret - One of the 2-4 pairs of nozzlelike appendages below the rear part of a spider’s abdomen,
through which silk is extruded and manipulated to form the strands of a web.


Thorax - The middle portion of an insect’s body, bearing the legs and wings.







Reference: Plant Galls of the California Region

                     Ronald A. Russo, 1979, Boxwood Press


Audubon Society Field Guide to North American Insects and

Spiders, Milne and Milne, Chanticleer Press, Inc. New York, 1980.


Insects,  Borror and White, Peterson Field Guides.


Butterflies of the San Francisco Bay Region,

J. W. Tilden, U. C. Press, Berkeley, CA. 1965.


Spiders and Their Kin, Golden Guide, Levi and Levi.


Butterflies and Moths, Golden Guide, Mitchell and Zim.


Insects, Golden Guide, Zim and Cottam.


Dr. John Hafernik, Professor of Biology, San Francisco

State University.