1915} : Behavior of Anopheles 247 
pipe was moved in the direction of ditch ‘‘B.”’ In places the 
pupae were so thick as to give the appearance of heavy moss. 
At regular periods large areas of very young larvae were 
encountered, indicating that breeding was far from stopped. 
On March 13th, about four gallons of top minnows were taken 
from the old French Canal. and transferred to the marsh, 
but these fish left no record of having in any way checked 
the numbers of larve. 
The chlorine-content of the water exceeded at times that of 
sea-water. When the fine silt began to mix with the water, 
the beginning of the end was plainly in view. Ditch ‘‘B”’ was 
deepened, while ““A’’ was closed. This allowed the fill to 
proceed toward “‘B.”’ By the end of June the paucity of 
larvee ‘was very noticeable and during July and the following 
months no breeding was encountered. 
B. LIFE HISTORY, 
1. The Immature Stages: The flight experiments and the 
daily examination of thousands of mosquitos, allowed but 
little time for a study of larve and pupe. The duration of the 
pre-adult stages of A. tarsimaculata were found to be as follows: 
egg-instar fifteen to twenty-four hours; larval stage from 
four to five days; pupal stage from two to three days; or, for 
the entire period, seven to nine days. Aedes taentorhynchus 
from the same locality matured about a day sooner. No 
distinguishing markings could be made out in the field with a 
10x lens which separate true albimanus from tarsimaculata. 
‘The pupe of the latter appeared to be darker in color, but from 
a series of pupz from other stations, this color difference 
proved to be valueless. To the sanitary inspector it is enough 
to group the species into several easily recognized divisions. 
Thus on the Canal Zone, the Anophelenes may be divided into 
(1) the albimanus group; (2) the malefactor group; and (3) the 
pseudopunctipennis group. 
Larve orient themselves readily to regions of shade. Sun- 
light, or any highly intense light, which may shine directly 
upon a mass of larve, causes great commotion among them, 
which excitement finally ends in shaded portions of the pool. 
A similar reaction ensues when a film of vegetable oil reaches 
larve. There is also a decided reaction to shadows that pass 
