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Dorymyrmex
bicolor Wheeler
Figures
202-203
Dorymyrmex pyramicus subsp. bicolor
Wheeler, 1906:342; o.
Dorymyrmex pyramicus var. bicolor:
Cole, 1942:371, 372; o.
Dorymyrmex pyramicus bicolor: Creighton,
1950:348, 349; o.
Conomyrma (Conomyrma) bicolor: Kusnezov,
1952:430; _.
Dorymyrmex bicolor: Cole, 1957:130.
Cole, 1966:18; o.
Wheeler and Wheeler, 1973:103?104; figs. 37, 38; o. Shattuck, 1994:75.
Snelling, 1995:13; o.
Conomyrma bicolor: Snelling, 1973:
4-5; o _ _. Martinez, 1995:252. Allred, 1982:458-459. Wheeler and
Wheeler, 1986:57. Martinez, 1995: ADD MARTINEZ HERE!
RANGE: Western Texas to southern
California; Nevada, Utah;
northern Mexico.
DESERT RECORDS. Map 4. Generally
distributed throughout our
area; 89 records.
DISCUSSION . This ant is easily
recognized, although in the field it can be confused with some bicolored
Myrmecocystus. The characteristic tapinomine odor, when crushed,
will readily identify D. bicolor. Nests of this aggressive
little ant often have very regular circular craters 5-7.5 cm in
diameter, but may also have a very irregular tumulus. Nests appear
to be clumped; these may be multiple entrances of a single colony.
Dorymyrmex bicolor is found
in open areas in habitats such as Creosote Bush Scrub and Saltbush
Scrub on the desert floor, Palm Oases, near sand dunes, on alkali
flats and in Joshua Tree Woodlands, but is most commonly encountered
in sandy Wash Woodlands. It occurs at elevations between -190 and
4300 feet.
Foragers move rapidly and generally
leave their nests to search for food in the late afternoon (1600
-1700). They forage throughout the night and into the morning hours
until about 0900. During cooler months, such as October and November,
they may be found foraging from 1200 untill 1500.
Workers have been found on several
different plants collecting nectar, resins and honeydew from homopterans.
Records include: Encelia farinosa, Ambrosia dumosa, Larrea tridentata,
Chrysothamnus nauseosus, Peucephyllum schottii, Stanleya pinnata,
Asclepias erosa, Datura discolor, and Chamaesyce spp.
Returning foragers have been intercepted
with the following items: other ant species (Pogonomyrmex maricopa,
Solenopsis xyloni, Pheidole gilvescens, etc.). flies (especially
Ceratopogonidae), Hemiptera (Lygaeidae, Miridae) and Homoptera (Cicadellidae).
Workers have been observed attacking Pogonomyrmex californicus
at the entrance to the Pogonomyrmex nest. Remains of S.
xyloni have often been found in great numbers at the base of
D. bicolor craters.
Martinez (1995) has suggested that
D. bicolor (as Conomyrma bicolor) usurps nests of
D. insanus (as C. insana). He reportedly observed
"both . . . emerging from the same nest entrances of four different
colonies." Unfortunately no observations were provided other
than that the mixed worker populations were noted in mid-June; by
1 July the nests included only D. bicolor. We consider these
observations to be merely anecdotal in the absence of convincing
detail; confirming observations are clearly necessary.
One question to be answered is why,
if D. bicolor truly does usurp nests of D. insanus,
workers of both species were seen emerging from the same nests with
no apparent aggressive interaction. In the same too brief note Martinez
stated that D. bicolor "eliminates colonies of [D.
insanus] by attacking their nests . . " and that while
he had "observed aggressive interaction between the two species"
none seems to have been evident in these cases.
Perhaps what Martinez actually observed
was evidence that D. bicolor is a temporary social parasite
of D. insanus, thus resolving a question that has vexed us
for years: why, considering the abundance of D. bicolor,
have we never found claustral females establishing new nests following
mating flights? Such females of D. insanus are commonly found.
Is it possible that newly mated females of D. bicolor enter
established nests of D. insanus, eliminate the host queen,
and thereby usurp the host worker population that is eventually
replaced by a pure D. bicolor population? This may prove
to be pure speculation; it seems strange that mixed nests have not
been observed before if D. bicolor is a true temporary social
parasite.
Alate females have been collected
at lights during the months
of April and May.
This species is preyed upon by the
flat-tailed horned lizard,
Phrynosoma mccalli.
ADD DISCUSSION OF RUTH BERNSTEINS OBSRVATIONS OF "SLAVERY"
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