268 Annals Entomological Society of America |Vol. VIII, 
(a) The apparatus was set up in front of a window. No 
mosquitos entered the upper chimney until the sun was low 
and dusk appeared. Then they appeared in large numbers 
and congregated about the gauze top. At dawn they also 
appeared on this gauze top, and they attempted to get away. 
(b) Repeated, excepting that the chimney was covered with 
light paper so as to produce within a semi-darkness not far 
from that of dusk. Apparatus set up in front of window in 
bright sunlight. Mosquitos entered the top chimney irre- 
spective of time of day. By removing the paper cover, they 
scrambled to get into the lower dark cage. 
(c) Modified by removing the gauze top of the chimney and 
by adding to this chimney another one. The top chimney 
and the bottom one were kept dark within. The middle 
chimney was kept in semi-darkness. Mosquitos entered middle 
chimney. The wrapping of this was then taken off, thus 
admitting bright light. The mosquitos flew into the upper 
dark chimney. 
These crude experiments and the field observations show 
that these mosquitos are attuned to that range of light intensity 
which occurs during dusk and dawn. When this optimum 
intensity is increased, the mosquitos become negatively 
phototropic. 
When hungry, mosquitos are positively chemotropic and 
this stimulus may alter the effects of intense light and lessen 
greatly those of heat. 
During flight the phototropic response is the dominant one. 
But observations seem to indicate a positive anemotropism, 
i. e€., an orientation with reference to the direction of the wind. 
The mosquitos seem to fly at a quarter to the wind. ‘The flight 
at Gatun was more than one mile and was made in one con- 
tinuous flight. The observations of Celli in Italy that Anopheles 
do not fly further than from two to three hundred and fifty 
meters, indicates a different set of conditions existing in Italy 
than in Panama. One of the very first things to do in malaria 
sanitation is to learn the species involved, which of these trans- 
mit malaria, and then scour the literature for all facts regarding 
the behavior of the disease-carriers. Then studies should be 
carried on to learn something definite about the flight factors, 
and these studies cannot be of value unless the entire environ- 
