1915] Behavior of Anopheles 223 
ACKNOWLEDGMENTS. 
The author is particularly indebted to Surgeon-General, 
Wm. Crawford Gorgas, formerly Chief Health Officer of the 
Panama Canal Zone; it is due to his efforts that entomological 
study on the Isthmus at this time was at all possible. To Mr. 
Joseph A. Le Prince, formerly Chief Sanitary Inspector, 
acknowledgments are due for his support and constant encour- 
agements throughout the work. 
The author is indebted to the following gentlemen for 
assistance given: Mr. James B. Shropshire, detailed to assist 
him; Dr. A. J. Orenstein, former Assistant Chief Sanitary 
Inspector; Dr. Samuel T. Darling, former Chief of Laboratory, 
Ancon Hospital; Mr. J. A. Corrigan, Sanitary Inspector at 
Gatun; Dr. E. Garcon of Gatun Dispensary; Sanitary Inspec- 
tors Messrs. C. B. Chinn, Geo. Parker, E. F. Quinby, C. H. 
Bath Chas. bP. Cratts,2A nk. Proctor and:S.P.. Verner. The 
writer acknowledges with gratitude the helpful criticisms and 
encouragements of Dr. L. O. Howard, Chief of the Bureau of 
Entomology, U. S. Dept. Agric., and of Messrs. August Busck 
and Frederic Knab of the same bureau. Only those intimately 
acquainted with mosquitos of tropical America, and who have 
worked under the enervating strain of its moist, hot climate, 
can appreciate the services rendered by these gentlemen. 
REGIONAL ORIENTATION. 
The Panama Canal Zone is a typical sample of the humid, 
torrid zone, characterized by an uniformly even climate, with 
very little seasonal change, with a wet and a dry season, a 
fairly heavy rainfall, high humidity, prevailing north and north- 
west winds, and a prolific and luxuriant biota. Of mosquitos 
alone it yielded about 130 species. For a good account of the 
Zone and the problems of mosquito control, see Jennings 1912, 
pp. 131-141. 
The town of Gatun is located seven miles from the Atlantic 
entrance, and is the site of three flights of locks which, in less 
than a mile, raises the level of water from sea-level to 85 feet in 
Gatun lake. To sustain this level of 85 feet in the lake, a num- 
ber of dams had to be built, the largest of them being the 
famous Gatun Dam, nearly 1.5 miles long and 105 feet high. 
