94 MORE MINOR HORRORS 



of development. Howard has pdinted out 

 that the addition of creosote or creosote-oil 

 to the water in which the larvae are living 

 hastens the metamorphosis into pupae, and 

 the pupa stage is passed through in as short 

 a time as fifteen hours instead of the normal 

 forty-eight hours of the warm waters of 

 the Southern States in America. It has also 

 been observed that showery weather hastens 

 the rate of development. 



When the adult mosquito is about to 

 emerge, a certain amount of air is secreted 

 under the chitinous casing of the pupa. A fine 

 streak containing air appears along the back, 

 extending between the respiratory trumpets 

 and the base of the head. This central streak 

 gradually passes backwards until it reaches 

 the seventh abdominal segment, and then 

 suddenly the pupa extends its abdomen so 

 that it floats parallel to the surface of the 

 water instead of being under the rest of the 

 pupa's body. The chitinous integument now 

 splits along the median dorsal line, and through 

 the slit thus made the thorax of the adult 

 mosquito now protrudes. By gradually press- 

 ing its abdomen against the pupa-case, the body 

 of the perfect insect is slowly but gradually 

 raised above the surface of the water. The 

 head is pulled backwards and upwards, and 

 millimetre by millimetre the mouth parts, the 



