Salton Sea Trip #4
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Ants At The

Salton Sea &

Blythe Area #1

Formicinae: Subgenus Endiodioctes: Myrmecocystus. For Latest ID See Addendum

Alex Wild includes images of three species of Myrmecocystus with reddish-orange heads and black abdomens (gasters) on his website: M. depilis (Portal, AZ), M. mendax (Chiricahua Mts, AZ), and M. mimicus (Sycamore Can, AZ). The latter species also occurs at Carrizo Plain National Monument, CA and Green Valley, AZ. The three species superficially resemble the following images of honeypot ants I observed north of Salton Sea State Park.

Myrmecocystus mimicus is common in southern California and this may be that species; however, the very similar M. flaviceps has been reported from north of the Salton Sea and the nearby town of Mecca.

Myrmecocystus mexicanus has been reported from the Salton Sea, but this species has an amber-colored head and body. Alex Wild includes images of this species from the Mojave Desert, CA plus images of two additional amber-colored species: M. navajo (Wilcox, AZ) and M. testaceus (Mojave Desert, CA). He also includes another species from sand dune areas of the Mojave Desert with a black head and body (M. tenuinodis). I have photographed M. mexicanus (or M. navajo) from Holbrook, AZ.

Numerous Myrmecocystus workers near the entrance to their nest in the heat of day. The air temperature at noon (4 May 2013) was 100 degrees Fahrenheit. This colony did not have a distinct crater-like mound like nearby harvester ants with piles of seedless husks from Atriplex polycarpa.

This is not Pogonomyrmex or Messor, two of the common harvester ant genera in this area. It is definitely an ant of scorching desert regions. It doesn't have piles of empty husks like havester ants. It feeds on live or dead insects and honeydew secretions. Myrmecocystus mexicanus is known from the nearby Salton Sea State Beach area; however, the latter species is orange-yellow. Alex Wild shows several species with red heads and dark bodies on his web site.

Even without special workers (repletes) that store honeydew in their swollen abdomens, it is possible to identify the genus Myrmecocystus by the above combination of distinguishing characteristics. This is especially true considering that this species lives in the scorching saltbush scrub adjacent to the Salton Sea. A stream of toxic formic acid is sprayed out of the acidopore, a lethal weapen for defense and warfare with other ant colonies.

The genus Myrmecocystus is commonly known as "honeypot ants." Worker ants tend special polymorphic ants (repletes) called plerergates. These unusual ants hang from the ceiling deep within the nest and are "living storage units." They store large quantities of nutritious honeylike fluid in their swollen abdomens to feed the colony during times of famine and drought. This is an adaptation for living in extremely hot desert environments with prolonged drought, such as the Salton Sea region. See the following image courtesy of Wikimedia Commons.

Honeypot ants hanging from the ceiling of Myrmecocystus nest. Photographed at the Cincinnati Zoo.
© Greg Hume 17 September 2006, Courtesy of Wikimedia Commons.

 See Amazing BBC Video About Honeypot Ants (Myrmecocystus mimicus) In Horseshoe Canyon, Arizona 

Honeypot Ant Craters

The entrance to this Myrmecocystus nest is within a shallow circular crater. Inset: Close-up view of entrance showing several workers.

Nest of Myrmecocystus on north side of Salton Sea. Although some entrances do not have a well-defined crater, this one is quite distinct. This may be related to the age of colony.

Crater-like nest of Myrmecocystus north of Blythe, California. Inset: Close-up view of entrance showing a worker. In general, the nests in this area have shallow craters with a relatively large circular entrance in center. They are not as well-defined as the craters of nearby harvester ants (Messor).

    According to Pinau Merlin (A Field Guide To Desert Holes, 2003): "Honeypot ant nests are hard to define, with no distinctive shape and no cone. The entrance hole is about 2 inches in diameter, and could be mistaken for a harvester ant hole."

In my opinion, harvester ant nests (Messor and Pogonomyrmex) usually have a distinct crater-like cone covered on the outside with dense layer of seedless husks from nearby shrubs and wildflowers. Myrmecocystus nests may have just a opening in the sand, or resemble shallow craters. Depending on the species and age of the colony, the crater-like nests of some Myrmecocystus can be quite distinct.

Acromyrmex versicolor (Leaf-Cutter Ant)

The crater is without piles of seedless husks as in nearby harvester ants (Messor and Pogonomyrmex). The crater resembles leaf-cutter ants in Arizona (Acromyrmex versicolor).

Addendum: Identification of Myrmecocystus North Of The Salton Sea

In conclusion, I am uncertain about the common bicolored Myrmecocystus (subgenus Endiodioctes) ants north of the Salton Sea. There may be more than one species. Myrmecocystus mimicus is common in southern California and this may be that species; however, the very similar M. flaviceps has been reported from this area. I have one photo of a honeypot ant from Box Canyon North of Mecca and the Salton sea that appears to be M. flaviceps. Tergum III has densely appressed hairs and the gaster is dull black compared with the glossy black gaster of M mimicus. M. flaviceps has been reported from Mecca, North of the Salton Sea, Joshua Tree National Park (Cottonwood Campground), Deep Canyon near Palm Desert, and the Algodones Dunes!

Correction: Tergum I In My Labeled Images Is Actually Tergum III

If you count the propodeum as tergum (tergite) I and petiole as tergum II, then the first tergum of expanded abdomen (gaster) is tergum III or tergum IV depending on whether there are one or two petiole nodes.

Myrmecocystus mimicus From Tehachapi, CA. Gaster Shiny
Black & Tergum III Not Covered By Dense, Appressed Hairs