LAEV.E IN BRACKISH WATER 289 



days ; Taylor of Havana places it at nine days. As already mentioned, Dupree 

 and Morgan, succeeded in obtaining imagos after from six to eight days. 



At Para, Goeldi conducted a number of experiments on the rapidity of de- 

 velopment of the yellow-fever mosquito. The duration of the entire cycle, from 

 the date of oviposition to the emergence of the imagos, showed a minimum of 

 twelve days and a maximum which was indefinite and almost unlimited, accord- 

 ing to the season of the year and the dearth or abundance of food. He ob- 

 served one case in which a male emerged only after fifty days, and other cases 

 where with the same number of days there were still larvae and pupae. 



The French observers determined a distinct relation between temperature and 

 the rate of development. At Eio in the most favorable season, when the night 

 temperatures were from 26° to 27° C. (■79°-81° F.) and the day temperatures 

 from 28° to 31° C. (82°-88° F.), they observed that some of the larvae of 

 calopus reached the pupal stage seven days after the hatching of the eggs, and 

 the adult condition on the ninth day, and generally most of the larvae from the 

 same laying of eggs produced imagos about the tenth day. They found that 

 when this rapid breeding occurred it was necessary that the egg as well as the 

 larva should have had the right temperature and the egg a rapid incubation. 

 The temperature being lower the evolution naturally becomes longer, and at 

 Petropolis, with a night temperature lower than 22° C. (72° F.), they found 

 the larvae taking from forty to sixty days to reach the pupal state, and from three 

 to five days longer before the perfect insect issued. Ordinarily, according to 

 their observations, the pupal stages last only from thirty to fifty hours. They 

 found that the larvae do not perish at a temperature near the freezing point, but 

 they grew very slowly and took an indeterminate time to become adults. 



The French investigators showed that the development of this species is 

 possible in brackish water, but that soapy water is very destructive to them. 

 They proved that in sea-water they perish quickly; that this is not true when 

 sea-water is mixed with fresh water. In one of their experiments a female, 

 placed in a tube containing five-sixths fresh water and one-sixth sea-water, laid 

 its eggs as under normal conditions. These eggs hatched at the end of four days, 

 and the larvae, reared in a jar containing the same water, reached the pupal 

 condition on the eleventh day and the perfect condition on the thirteenth day. 

 The same result was reached when larvae were placed in brackish water con- 

 taining one-fifth sea-water and four-fifths fresh water, but two young larvae 

 placed in brackish water containing one-third sea-water perished at the end of 

 a few hours. 



RESISTANCE OF LARV^ TO ADVERSE CONDITIONS. 



The Brazilian investigators made an extensive series of experiments to de- 

 termine the effect of brackish water of different degrees of salinity. They found 

 that in a mixture of 30 per cent sea-water with 70 per cent fresh water the larvas 

 transformed to imagos in a normal manner, although development was retarded. 

 They found larvae of calopus in nature in brackish water containing 35 per cent 

 sea-water. With 40 per cent sea-water the larvae still survived and a few pro- 



