MOSQUITO BREEDING IN SALT AND FRESH WATER. 337 



CLIMATE AND TEMPERATURE. 



The inhabitants of the region about Cervantes state that the temper- 

 ature at that point, in the daytime during the dry season, is little if 

 any lower than that of Manila, and certainly this was so during my 

 stay there; the average day temperature was 30°, the night temperature 

 25°, which was even higher than in Manila. At Sagada the thermometer 

 ranges at a very much lower point, while at Bontoc it is slightly lower 

 than at Cervantes. 



Cervantes is surrounded by hills on all sides except toward the north, 

 and so the town is cooled only to a moderate degree, even during the 

 monsoons, by the breezes which blow from that direction. The breezes 

 become heated by passing through the valley from the northern ex- 

 tremity and find no outlet at the south; hence Cervantes during the 

 dry season is subjected, as it were, to an almost continuous sirocco-like 

 wind, which circulates and recirculates within the bowl-like valley. 



This region, like others in the Philippines, is subject to occasional 

 showers during the dry weather, but at Cervantes these are very in- 

 frequent. 



CHARACTER OF THE RIVER AND SPRING WATER. 



While the water in this region is strongly impregnated with lime, one 

 of its peculiar features appears to be its large content of aluminium 

 sulphate, which is also a characteristic of the water found in the breeding- 

 places of Myzomyia ludlowii Theob. at Olongapo. Many of the .springs 

 near Cervantes are hot and the water from these and the cold ones 

 evaporating during the dry season, leaves an incrustation which when 

 analyzed in the laboratory yields, approximately, 33 per cent of alumi- 

 nium sulphate. 



OBSERVATIONS ON MOSQUITO LARVAE. 3 



The larva? of M. ludloivii Theob., found in the Province of Lepanto- 

 Bontoc, were always observed in water in which algae were growing, 

 either floating on the surface or attached to the stones over which the 

 water trickled. This same fact was noted in a previous publication 

 referring to the same species of mosquito at Olongapo. Those observed 

 in streams from springs were most abundant where there were slight 

 depressions in which water a half centimeter or more in depth might 

 collect; in the rivers they were always encountered where an obstructing 

 rock or the friction of the bank caused either a back current or an eddy 

 and where the water was comparatively still. It was very difficult to 

 discover the larvae in such situations except during periods of the 

 brightest sunshine and then only when, after disturbing the surface, 

 the investigator patiently awaited their reappearance at the top. Any 



3 This Journal, Sec. B. (1907), 2, 518. 



