1915} Behavior of Anopheles 245 
was the real cause of so many of these pests being within. Once 
in, and finding the electric lights too intense, they remained 
under the tables. The Y. M. C. A., close to the hotel was 
relatively free from mosquitos, due to the fact that the door was 
not situated the same as the hotel door. 
It is impossible to estimate the number of mosquitos which 
paid daily visits to Gatun, and were any true statement made, 
it would appear fictitious. At the cement shed, close to the 
breeding place, cob-webs were so heavily loaded with mosquitos 
that they sagged and were torn in places, (Zetek 1913-b). 
The presence of so many mosquitos in these cob-webs is explain- 
able by the fact that mosquitos inside of the building always 
aim to get out at dawn, at least so has been found to be the 
case over and again, and there being many cob-webs about the 
windows, large numbers of mosquitos were caught in them. 
The spiders do not seem to care for mosquitos. To be stranded 
at the breeding place was a most painful trial, though unusually 
fruitful in results. 
Sweep-net catches showed mosquitos harboring in the low 
grass whenever the day was foggy or cloudy, but in clear, 
warm days, but few were found in such grass. Cracks in the 
soil were found to harbor Anopheles (also black flies). The 
shaking of bushes near the breeding place frightened away 
veritable clouds of Anopheles and Aedes. By placing a negro 
within a mosquito bar net having one side slightly raised and 
exposing same during dusk (at the breeding place), there were 
attracted into that net a trifle over three thousand Anopheles, 
actual count, which represents about a hundred mosquitos 
entering the net each minute. 
Ocular inspection at the right time of the day—at dusk 
and during dawn—sufficed to detect a noticeable flight of the 
mosquitos to Gatun from the salt-marsh. Marking the adults 
with anilin dyes was done only to clinch the facts, to prove 
beyond all doubt that the mosquitos seen in flight really were 
bound for Gatun. 
The remedial measures pursued to stop this immense 
breeding were the digging of two drainage ditches and the 
reclamation of the marsh by hydraulic fill. The trees and 
jungle at the peninsula fronting the breeding area were cut and 
burned over by February 4, 1913 and the smoke and the destruc- 
tion of a large area of shelter were effective in reducing for the 
