W. M. Wheeler.
The Pleometrosis of Myrmecocystus.
Psyche 24(6):180-182, 1917.

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180 Pwche [December
by the large size and dark color of the ants and their wings, the stillness and purity of the air and the unobstructed view over the -
level desert. Unfortunately our haste to reach Phoenix before night and the prospect of a very muddy road ahead, made it im- possible to stop and observe the conclusion of the flight and the subsequent behavior of the versicolor queens, On previous visits to Arizona I had found the species in the neighborhood of Bensony Tucson and Yucca. The past summer I took it also near Oracle in the Santa Catalina Mountains, near Casa Grande and a few miles from Texas Pass on the western slopes of the Dragoon Mountains. In all these localities the colonies are sporadic and by no means abundant so that it is difficult to account for the vast number of males and females engaged in the flight described above, unless we assume that they represented the entire annual sexual output of a large number of colonies distributed over a very extensive territory.
THE PLEOMETROSIS OF MYRMECOCYSTUS,
BY WILLIAM MORTON WHEELER.
'
It has long been known that the colonies of some species of ants never possess more than a single fertile queen, whereas in other species several such queens are normally present. Wasmann has recently named the former condition "haplometrosis," the latter < <
pleometro~is."~ Among North American ants the species of ~
Camponotus, Polyergus, Pogonomgrmex, Aphcenogaster and Lasius are normally haplometrotic, whereas the species of Formica, Tapinoma, Crematogaster, Pheidole, Monomorium and Mgrm&u are pleometrotic. This condition undoubtedly arises in most colonies secondarily from a primitive haplometrosis through the dealation and adoption of one or more daughter queens. Large colonies of Formica obsxriventris, e, geY often contain a number of daughter queens in various stages of dealation. The number of queens thus accumulated in some colonies is considerable. I have counted more than thirty in a single medium-sized colony of the typical F. fusca, and a single mound of F. exsectoides may contain nearly 1These tema are equivalent to "monogyny" and ''polygyny'' employed by ~tudenta of the mcid waBpa, though somewhat more expressive as they call attention to the maternal or nun- ing activities.




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19171 Wheeler-The Pleometrosis of ~~~mecoc~~tus 181 or quite as many.
Occasionally, however, the pleometrosis is primary.
In other words, two or more queens may establish a colony together.
Forel, Bonner and I have found cases in which two queens of the European Lasius $avus 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, Mrkzek 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 Expedition9 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 in the 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 M~rmecocptus mellige~ Fore1 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



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