Psyche 
[September 
170 
few colonies were also noted in dead branches, down to one inch in 
diameter, on living trees in the same areas. An incipient colony was 
found by George Hofer in the sapwood of a dead palo verde ( Cerci - 
dium sp. ?) in Sabino Canyon (Banks and Snyder, 1920). The 
fairly large colony from Guaymas, Sonora, was from a short branch, 
one inch in diameter, on a living palo verde (species?). Burger took 
a very large colony in a fragment of palo verde (species?) trunk, 
about six feet long and 10-12 inches in diameter, partly buried in 
the sand of Alamo Wash. A colony in a “palo verde stump” was 
sampled by C. C. Lamb at La Paz, Baja California del Sur (Light, 
1929). 
There are three or four species of Cercidium , one or more of which 
are very abundant and characteristic trees in various parts of the 
Sonoran Desert. In the Arizona Upland, and probably elsewhere 
in their ranges, C. floridum is more abundant on upper bajadas and 
along drainageways, while C. microphyllum prefers hills, outwash 
slopes and plains. There seems to be no reason why Pterotermes 
should not utilize the wood of all these species wherever they occur. 
In the Tucson Mts. Werner collected specimens from a colony 
in a disintegrating saguaro skeleton. The only other association with 
this wood was the small colony in a single rib, about one inch in 
diameter and a few feet long, found on the open desert floor in the 
Ajo Mts., also by Werner. Cereus giganteus is prominent over most 
of the Arizona Upland and the Plains of Sonora, but it is absent 
from the Foothills of Sonora and Baja California. Extensive collect- 
ing has been done in southern Arizona for termites and other xylo- 
phagous insects for many years. Since Pterotermes has not been 
found in any other wood (mesquite, Prosopis juliflora , and ironwod, 
Olneya tesota for example) it is not improbable that the palo verdes 
and saguaro provide the most suitable nesting sites in this part of 
the desert. 
In the remaining subdivisions of the Sonoran Desert, however, 
there is a different and even wider selection of woody plants which 
should be searched for Pterotermes ; for example, the dead skeletons 
of other large columnar cacti in the genera Cereus and Pachycereus. 
The only additional host data accompany the collection made by 
J. A. Powell from Canyon del Tajo, Sierra Juarez, in northern 
Baja California. “These specimens were taken in dry (1952) flower- 
ing stalks of Yucca whipplei on the trail down into the canyon 
probably at an elevation of about 3000 feet.” Powell also added 
that “I have subsequently examined stalks of this host over a wide 
range in California from perhaps 40 or 50 localities in connection 
