APPENDIX 10 
REPORT ON THE CANAL ZONE BIOLOGICAL AREA 
Sir: It gives me pleasure to present herewith the annual report of 
the Canal Zone Biological Area for the fiscal year ended June 30, 1948. 
TWENTY-FIFTH ANNIVERSARY 
On April 17, 1948, the island laboratory celebrated its twenty-fifth 
anniversary. A special commemorative 10-cent stamp was issued by 
the Canal Zone, consisting of an outline drawing of the island, and 
within this the gato-solo (coati-mundi), the most versatile, intelligent 
mammal of the island. First-day covers, containing the 1947 annual 
report, were sent to those who had been on the island during the past 
25 years, and many very interesting repliey were received. 
SCIENTISTS AND THEIR STUDIES 
Dr. T. C. Schneirla, curator of the department of animal behavior of 
the American Museum of Natural History, continued his studies on 
army-ant behavior, assisted by Dr. Ernst Enzmann, of the Harvard 
Biological Laboratories, and by R. Z. Brown, of Swarthmore College. 
They “investigated the behavioral and biological conditions of two 
army-ant species, Heiton hamatwm, a typical column raider, and 
E. burchelli, a typical swarm raider. The studies were begun in early 
November 1947 and continued through March 1948, thus starting late 
in the rainy season and extending well into the latter part of the dry 
season.” 
The study was concerned particularly with the manner in which 
army-ant colonies adapt to dry-season conditions, and the manner in 
which these ants produce their fertile females (dichthadiigynes). The 
project was designed to complete a general investigation on army-ant 
behavior and biological conditions begun in 1932 on Barro Colorado 
Island. 
As a result of the findings, it is now clear that but one sexual brood 
per colony appears annually in the army ants, and that the pre-con- 
ditions of this brood are peculiar to the dry season. With further 
information about the timing of the one sexual brood per year and 
the conditions of its production, the implications of the army-ant situ- 
ation for problems of caste and sex determination now are clearer. 
137 
