1917] Wheeler—The Pleometrosis of Myrmecocystus 181 
or quite as many. Occasionally, however, the pleometrosis is 
primary. In other words, two or more queens may establish a 
colony together. Forel, B6nner and I have found cases in which 
two queens of the European Lasius flavus were starting a colony 
in the same small cavity under a stone. Donisthorpe has seen 
three and Crawley and Wasmann four queens of this species in 
similar association. On two or three occasions I have also seen 
twin queens of our North American L. brevicornis with young 
brood under a stone. In some of these cases the colony undoubt- 
edly becomes secondarily haplometrotic by one queen killing the 
other or by the colony splitting into two, each with its own queen. 
According to von Buttel-Reepen, Mrazek and Crawley, this 
seems to be regularly the case with L. niger, when two or more 
queens are constrained to found a colony together in an artificial 
nest. 
The following observation, made during the past summer while 
I was with the Cornell Biological Expedition, throws some ad- 
ditional light on primary pleometrosis. On July 29 the heaviest 
rain in six years fell in Phoenix, Ariz., and temporarily inundated 
parts of the desert south of that city in the neighborhood of Higley. 
On July 30 we left our camp about 30 miles north of Florence and 
proceeded along the road to Phoenix over soil which had been 
drenched by this rain, with the result that our three motor cars 
were repeatedly stuck inthe mud. While the younger and lustier 
members of the party were extricating our cars and two others 
which had been stalled all night in deep puddles, I took advantage 
of the delay to study the ants along the roadside. Many colonies 
of various species, whose nests had been inundated, were moving 
to drier ground. My attention was especially attracted by dozens 
of incipient nests of Myrmecocystus melliger Forel subsp. mimicus 
Wheeler. The large reddish queens had evidently celebrated their 
nuptial flight immediately after the storm and were now busily 
digging into the wet adobe soil, making small craters about two 
inches in diameter with eccentric opening. ‘The wall of the craters 
consisted of small pellets about one-eighth of an inch in diameter, 
evidently carried up in the psammophore, or crate of peculiar 
stiff hairs with which the gular surface of the head is furnished in 
these ants. On seizing a queen just as she was carrying out and 
dropping her pellet on the wall of the crater I was surprised to see 
