RESISTANCE OF THE LARV/E AND EGGS 153 



desirous of obtaining specimens and examining them, 

 otherwise they wriggle very rapidly to the bottom. 

 Another point has also to be borne in mind, and 

 that is, that they cling to the sides of the receptacle 

 and hide in the crevices, so that it is by no means 

 easy to get rid of them. Simply emptying the water 

 out of the receptacle will not suffice ; a very thorough 

 rinsing and cleansing is necessary. The duration of 

 the larval period is from six and a half to eight days 

 normally ; but, of course, they may remain in the 

 larval stage for a much longer period ; for instance, 

 I brought some specimens alive to Liverpool which 

 I collected at Puerto Barrios in Guatemala, on 

 October 26. They were kept in a large test-tube 

 either in my pocket or in my living room, and they 

 were exposed to great variations of temperature, the 

 cold increasing as I travelled from New Orleans to 

 New York, and from New York across the Atlantic 

 to Liverpool. The journey occupied twenty-five days, 

 and they were only supplied with clean water. The 

 larval stage is succeeded by the pupa stage, which 

 lasts tw^o days or under, and from the pupa arises 

 the image or winged mosquito. 



Dr. Francis of the United States Marine Hospital 

 Service reported, on March 25, 1907, upon many 

 interesting points in connection with the life cycle of 

 Stegomyia calopus, as observed in Mobile. Amongst 

 them he mentions that larvee were never found breedinsr 

 in the unpaved street gutters or ponds, or in fact in 

 any natural earth-bottoms, but were always in artificial 

 water-containers. The eggs may retain their vitality 



