446 NELSON C. DAVIS AND RAYMOND C. SHANNON 



Although pseudopunctipennis appears equally domestic at all 

 times, the cool evenings in April, when most of the captures were 

 made, may have modified its feeding habits to a certain extent. 

 Although the total number emerging may have been reduced, an 

 unusually high percentage of these may have sought shelter in 

 houses. On the other hand, the people probably protected 

 themselves more at night with bed-covers than they would have 

 done during the summer, and thus have forced the mosquitoes to 

 feed more on animal blood, 



In the captures made near the Rio Salí, we found that first 

 visits yielded 48 female anopheline mosquitoes per house, while 

 subsequent daily visits gave 36.4 per house. Henee, a con- 

 siderable daily turnover took place. The house visits at Con- 

 cepción, made at intervals of several days, gave an average of 13 

 female anophelines per positive house. 



There was a tendency for more freshly-fed mosquitoes to occur 

 in the later captures made in certain houses. Thus, in houses 

 nos. 1, 2 and 4, Rio Salí, where several consecutive searches were 

 made, only 33 per cent of 255 captured at first visits were con- 

 sidered suitable for examination, while of 508 caught at sub- 

 sequent visits, 39.5 per cent were examined. This, in conjunction 

 with figures on concentration per house, suggests that some few 

 mosquitoes stayed more than one night in a dwelling. In the 

 whole series (Rio Salí and Concepción) , approximately 40 per cent 

 of all females caught were later examined. 



Among the female mosquitoes considered unsuitable for 

 examination (i.e., those without freshly ingested blood), no 

 statistical distinction was made between those presumably unfed 

 and those with traces of former blood meáis or with developed 

 ovarles. 



The anophelines captured near Rio Salí showed 2.2 per cent 

 males. The Concepción captures yielded 10.4 per cent males. 



At the Concepción hospital 225 anophelines were caught during 

 the period of two months (April and June). Of these, 33, or 14.7 

 per cent, were males. Of the 192 females, only 52, or 27 per cent, 

 were considered suitable for examination. Of the small number 

 examined, 19.2 per cent were negative, and only 30.8 per cent 



