A LARGE BOMBUS NEST FROM MEXICO^ 
By C. D. Michener and W. E. LaBerge 
University of Kansas, Lawrence, Kansas 
Although many aspects of the bionomics of temperate 
climate bumblebees are rather well known, little has been 
published on the biology of tropical species. It therefore 
seems worthwhile to make known the observations result- 
ing from the excavation of a nest of Bombus medius Cres- 
son. The nest was found at the edge of second growth 
jungle beside a field 15 miles south of Pujal, San Luis Potosi, 
Mexico, on June 21, 1953. This is in a region shown as 
tropical evergreen forest in Leopold’s (1950) vegetation 
map of Mexico. It is near the town of Tamazunchale, on 
which the following climatic data is available: Rainfall 
average 63.4 inches per year, most of it falling during the 
months of June to October. Monthly temperature averages 
range from 63°F. for January to 81°F. for July and 
August. Minimum temperatures probably reach freezing 
only once in many years. The bee is a tropical species, 
ranging from tropical Mexico to Paraguay. 
The nest was about four inches below the surface of the 
ground in a hollow which may have been an old rodent 
nest. The entrance was a hole about 1.5 inches in diameter. 
The hollow in which the nest was located was partially 
filled with decaying strips of bark, leaves, twigs, and the 
like, on which termites were feeding. The nest itself con- 
sisted of an irregular mass of cocoons and cells 10.5 inches 
in maximum diameter, nearly as large in other diameters, 
and three to four inches thick. Some of the cocoons were 
old, their walls whitened with fungus. Some of these old 
cocoons (about 10%) were filled with honey and sealed. 
As elsewhere in the nest, no cocoons used for honey storage 
were elongated with wax before sealing. For the most part 
these very old cocoons were at one side of the nest and on 
its lower surface. The bulk of the nest was made up of 
^Contribution No. 871 from the Department of Entomology, University 
of Kansas, Lawrence, Kansas. 
63 
