1915} Behavior of Anopheles PA 
A. MontTHLY WIND MOVEMENT, GATUN, C. Z. 
1. Direction, Hourly Periods. 
North Northwest West | North- East | Calms | Total 
1913 east 
No. | q No. oe Nose No. | q No. % \No. % | 
Waite sah 495 | 66.5 NOE PAB NAG TAG.) P44) Be) ont |] a) Ao 744 
IMKeS. - DAO ME i22 Owl el Galeton oul On lester es. oi eretctaleee alee needles 744 
2. Miles per Hourly Periods. 
ane see 63/9 SOS Os MI S0Ge hl G SOR olO noe On a ON e2eM ital: stele alee eeslene Sleep 
Mar olay 0 | BON aless3 Ab Bal PAD) |e le salle alleles Bile eel) woes: 
These first three months of the year are within the dry 
season. This period begins the latter part of December and 
extends well on into April, though some years it may appear 
sooner or be much delayed. It is not rainless as the name would 
imply, for at least every third day some rain falls. But as this 
dry season advances, the trade winds increase in velocity and 
become more confined to the north. In March, for instance, 
there are ten percent more north winds than there were in 
January; in mileage this was an increase of over eleven percent. 
During March, ’14, the writer had been in Boquete and 
David, Chiriqui Province, near Costa Rica. The north winds 
were so dominant here and of such high velocity that the trees 
on the plateau leading to Boquete are limbless on the wind- 
ward side, and their trunks are bent to leeward. Riding on 
horseback against this fierce wind, along the llanos of Santa 
Cruz and Dolega, was an experience which cannot be forgotten. 
Everywhere, everything told of its struggle to remain, even 
though so powerful a wind aimed at its destruction—present- 
ing a field of intense interest to the ecologist. 
A significant feature of these winds is their daily hourly 
range. The mean wind velocity of the months of January and 
March is plotted on.curve, chart ““B’’. Excepting for differ- 
ences in velocity, the two curves agree. The crest is at mid- 
day. The winds show a steady diminution in velocity from 
about midnight till about 7:00 a. m., and a like, but more 
decided decrease from about 2:00 p. m. till about 9:00 p. m. 
