Chalybion californicum

Geographic Range

The blue mud wasp, Chalybion californicum, occurs throughout North America, from southern Canada south to northern Mexico (O'Brien 1998).


This species is found in many different habitat types, anywhere flowers, spiders, nest sites, and a little water may be found (O'Brien 1998).

Physical Description

These wasps are metallic blue, blue-green or blackish in color. Males 9mm to 13mm (3/8in.-1/2in.) are typically smaller than the females at 20mm to 23mm (3/4in.-7/8in.) Both the males and females share similar body structure in that their waists are short and narrow; both having slight body bristles. The antennae and legs are black for both male and female. The wings of both the males and females are opaque and tinted the same color as the body (Hogue 1974).


We don't know much about courtship or mating in this species. They probably only need to mate once, though may mate more often. "Sleeping" aggregations (see Behavior) may also be part of the mate-finding process (Bohart and Menke 1976).

During the summer, female blue mud wasps build nests by bringing water to abandoned mud nests made by other species of wasps (mainly the genus Sceliphron). They form new mud chambers, stock them with paralyzed spiders and a single egg, then seal the chambers with more mud. Their offspring stay in the chamber, feeding on the spiders, and then pupating in a thin silk cocoon. They spend the winter in the nest, emerging the following spring as adults (Baker and Bambara 1999, Bohart and Menke 1976, O'Brien 1998).


Blue mud wasps are not known to be aggressive and will not usually sting unless provoked to do so. They are typically a solitary species using their stingers only to paralyze prey spiders and other insects they might encounter (O'Brien 1998, Baker and Bambara 1999).

Sometimes this species is found in groups, sheltering during the night or during bad weather (Bohart and Menke, 1976).

Food Habits

Adults of this species feed on flower nectar, and possibly pollen. Individual wasps get most of their nutrition while they are larvae, feeding on spiders provided by their mother. Adult females capture orb-weavers (family Araneidae) and comb-footed spiders (family Theridiidae), often including black widow spiders (genus Latrodectus). These wasps capture their prey by paralyzing them with a sting. Some have been observed landing on orb webs and luring the spider out of its retreat, captureing and paralyzing the spider without getting caught in its web and becoming prey itself (Bohart & Menke 1976, Hogue 1974, O'Brien 1998).

Economic Importance for Humans: Positive

This species may help to control the population of black widow spiders (O'Brien 1998).

Economic Importance for Humans: Negative

This species sometimes nests around buildings, and may thus be a small nuisance, but its inoffensive habits and use of spiders as prey generally prevent it from being a pest (Bambara and Becker).

Conservation Status

This species is common and widespread throughout North America, and is not considered in need of special conservation efforts.

Other Comments

The genus name, Chalybion, is from the Greek word chalybos, meaning "steel" or "metal," and refers to the metallic blue coloring of these wasps (Jaeger 1947).


Andrew Eulberg (author), Fresno City College, Carl Johansson (editor), Fresno City College.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

native range

the area in which the animal is naturally found, the region in which it is endemic.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


Arnett Jr., R. 1985. American Insects. New York: Macmillan of Canada.

Baker, J., S. Bambara. 1999. "North Carolina Pest News" (On-line). Accessed February 21, 2001 at

Bohart, R., A. Menke. 1976. Sphecid Wasps of the World: a generic revision. Berkeley, California, USA: University of California Press.

Charles L. Hogue, 1974. Insects of the Los Angeles Basin. Los Angeles: Natural History Museum Foundation.

Jaeger, E. 1947. A Source-Book of Biological Names and Terms. Springfield, Illinois, USA: Charles C. Thomas.

Mark F. O'Brien, 1998. "The Sphecid Wasps of Michigan" (On-line). Accessed February 25, 2001 at