Arthropods

Evidence of the range of arthropod species existing in the Baldwin Hills Natural Area is limited to the collection of evidence located at the Natural History Museum of Los Angeles County. In a recent study urban ecologist attempted to sample the existing fauna by breaking down the arthropod title into several subgroups. This page will provide information on the moths and butterflies (Lepidoptera), beetles (Coleoptera), ants, bees and non-parasitic wasps (Hymenoptera) and spiders, scorpions (arachnida). These subgroups were selected based on the ease at which one can identify the species and local expertise.

The Baldwin Hills natural area is home to both native and exotic arthropod species that rely on the diversity of flora found in the area. Researchers discovered that the loss of coastal sage scrub habitat also leads to a reduction of native arthropod species, as many rely on the one abundant coastal sage plant specimens for food and shelter. A major example of this relationship is the example of buckwheat and butterfly species. The isolated and sparse existence of buckwheat in the study area, raises concerns that the area might fail to support different butterfly populations.

A recent study found that the exotic arthropods, argentine ant, pill bug and earwig thrived in the Baldwin Hills natural area. These introduced species evolved outside of the context of Los Angeles, and do not have to worry about predators, parasites or tough competition. The introduction and proliferation of exotic species creates new competition for the native arthropods. Of the native species the ones most sensitive to increased competition, are the species that rely on a small type of habitat and resources to survive. Unlike the more sensitive native species, the generalists are able to adapt to the changes that both humans and the exotic fauna have brought.

European Honeybee (Apis mellifera)
Created in Czech Republic, north-east Bohemia

Ales Tosovsky via wikimedia

 

Do you like honey? Then take a quiet moment to thank the European Honey Bee. Originally from South Asia, the habitat of this species has been dramatically increased thanks to human migration. Europeans brought the bee with them across the Atlantic ocean in the midst of the 17th century, where they eventually found their way to the pacific shores in California.  These bees are known for the creation of honey, a product that humans have used and enjoyed for centuries. One can tell the honey bee apart from a bumble bee by its smaller and more slender size, and difference in coloring.

California Black-faced Bumble Bee (Bombus californicus)
Bombus_castilleja_(23755590341)

2.0 via wikimedia

 

The California Black-faced Bumblebee is part of the larger bumble bee family. These bees are identified by their size (often larger than their European counterparts). The California Black-faced Bumblebee evolved to have yellow hair on the second body segment, while the rest of the abdomen and face grow black hairs. These are “loud” insects and one can often hear the hums of their wings when the bee is close by. Like all other bumble bee species the California Black-faced bumblebee colony will die in the winter,      and reborn by the queen for the coming spring.

 

Yellow-faced Bumble Bee (Bombus vonesenskii)
Bombus_vosnesenskii_(23838057375)

USFWS via wikimedia

 

The Yellow-faced Bumble bee is part of the larger bumble bee family and evolved to have yellow hair on the fourth body segment and the face.These are “loud” insects and one can often hear the hums of their wings when the bee is close by. Like all other bumble bee species the California Black-faced bumblebee colony will die in the winter, to later be reborn by the queen for the coming spring.

 

Western Tiger Swallowtail (Papilio rutulus)
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Kevin Cole via wikimedia

 

With a wingspan of up to 4 inches, The Western Tiger Swallowtail is classified as a large species of butterfly. The Western Tiger is recognized by its bright yellow wings, marked with several black stripes extending down at various lengths. The Swallowtail originally adapted for riparian habitats, can now be found in both urban and suburban human settlements. In its early stages of life as a caterpillar, the Western Tiger’s most popular food choices include the local willow, sycamore, and alder.

 

Anise Swallowtail (Papilio zelicaon)
800px-Anise_Swallowtail

Linda Tanner via wikimedia

 

The Anise swallowtail is slightly smaller than its Western Tiger counterpart, (3.5 inches vs 4 inches wing span). The wing pattern of the Anise Swallowtail follows the yellow and black color combination, but lack the consistent black striping pattern. The habitat area of the Anise swallowtail has severely diminished due to the reduction of Los Angeles’ Sweet Fennel (Foeniculum vulgare) population. The Anise swallowtail relies on the sweet fennel plant to serve as a host for the butterfly’s eggs and larvae. Alternative host plants include carrots and parsley that might grow in surrounding gardens.

 

Sun Spiders (Solifugae)
800px-3453_Sun_Spider_2011

Galliasm via wikimedia

 

The nocturnal sun spider’s large pair of jaws might frighten the casual hiker who crosses its path. However, there is no need for concern, as the sun spider does not posses a drop of poison, or a stinger on any part of its body. These spiders are rarely seen in the Los Angeles area,  as they tend to prefer the hot and dry climate of the surrounding desert. These spiders are classified as small to medium sized arachnids, and grow to become .5 to 2 inches in length. The sun spiders developed the ability to climb smooth surfaces (including glass!) thanks to its suckers at the end of its two main appendages.

 

Trap-door Spiders (Bothriocyrtum californicum)
TrapDoorSpiderDorsal

davefoc via wikimedia

 

Once a common species in the Los Angeles basin, the trapdoor spiders are now seen as a rarity in the area. The reduction in trapdoor spider population, like many other species, can be traced back to the rapid expansion of human settlement across the LA basin. The spider changes in size depending upon its gender. Females tend to measure in 1 – 1.5 inches in length, while males range from .75 – 1 inch. The name ‘Trapdoor’ originates from the spider’s nesting habits where the spider constructs a tunnel lined with a self produced silken sheet, capped by a camouflaged door that the spider swings open to pounce on prey passing by.

 

Stink beetles (Eleodes sp.)
Desert_Stink_Beetle_-_Flickr_-_treegrow

Katja Schulz via wikimedia

 

The stink beetle is sometimes also referred to as an “acrobat beetle”. When interrupted by humans or other species, the beetle will assume a head standing position and place its rear side up into the air. This species of beetle developed its name from the faint foul odor it can release when being touched or moved. The stink beetle is found across large portions of the Los Angeles basin, and tend to inhabit more topographic areas. They are classified as medium to large beetles ranging in length from 1 – 1.25 inches. The beetle’s diet consist of seeds, and the roots of many LA plants.

 

Argentine Ant (Linepithema humile)
Argentine_ants_accessing_trap

Thmazing via wikimedia

The Argentine ant is the small black insect that is responsible for intruding into your house or yard in search of food and water resources. The ant is the most common species in Los Angeles and originates from Argentina and Brazil. In the late 1800’s the ant first found passage to the United States into New Orleans through coffee and other trade endeavours, and has spread over the United States. The Argentine ant is highly competitive and will seek out and destroy competing ant species within its territory. In addition to the ants’ constant search for food inside of human development, this species also protect and assist in the development of common garden pests (aphids and scale).

 

Thief Ant (Solenopsis molesta)
MolestaCA1

Alex Wild via wikimedia

 

The thief ant is smaller than its non-native Argentine ant competitors and also find its way into human settlements in the quest for food resources. These ants tend to favor foods high in protein and fat content, and are often able to sneak into food containers. Naturally this species eats dead insects, and its diet has been supplemented by human development. The name thief ant derives from the species’ ability to live inside or close to other ant nests, as they are skilled in the art of thievery.

 

Common Pillbug (Armadillidium vulgare)
Pillbug_(17152476067)

Brian Bratwicke via wikimedia

 

The common pill bug is known for its ability to roll into a ball when disturbed. The insect is ⅜ inch long and survives off a diet of young or rotting plant materials. The pill bug’s natural defense mechanism includes foul secretions from specific glands into its body. The bug is most prevalent in winter and spring, when there is more water. During the dry hot months, the bug migrate into subsurface soil levels where they wait for the rain to return. The common pillbug originates from Europe, and has since been introduced to large portions of North America.

 

European Earwig (Forficula auricularia)

 

European_Earwig_-_Flickr_-_treegrow_(1)-2

Katja Schulze via wikimedia

 

Originally introduced into the Los Angeles basin around the 1930s, the European earwig has become widespread across the area. The earwig’s diet consist of other insects, which it uses its rear pinchers to catch, seeds, young plants, and garden crops. In addition to its rear pinchers, the earwig also has the ability to produce noxious secretions from its abdomen to fend off threats. Unlike other insect species, maternal relationships are highly complex for the earwigs. In the spring one can often find female earwigs protecting her eggs or freshly hatched offspring. The European earwig is a light brown color and does not have banded appendages (unlike the darker brown ring-legged Earwig).

Additional Arthropod Information

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For more information:

  1. Arthropods of the Baldwin Hills – Louis LaPierre and Pamela Wright (2001)

Additional sources:

  1. Hogue, Charles Leonard. “Insects of the Los Angeles basin.” (1974).
  2. SFSU Bumble Bee Study

 

 

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