CONDITIONS OF LARVAL LIFE 27 



growth the fly-larva sheds its skin twice, each moult 

 leaving the maggot larger and darker. During the third 

 phase it becomes rounded up to form the chrysalis. 

 The larval period lasts about five days usually ; but this 

 stage may be prolonged in cold weather, or it may be 

 actually delayed for long periods the caterpillar falls 

 into a state of lethargic hibernation in the winter 

 months. Newstead, writing about his observations in 

 Liverpool, remarks that fly-larvae mature quickly 

 (five days) in a temperature between 90 and 98 

 Fahrenheit if they have plenty of fermenting food, 

 but that when the temperature of their surroundings 

 reaches 100 Fahr., they leave the hotter portions 

 of the manure-heap and crawl to a cooler spot. I 

 found that in Cairo flies were the most numerous 

 about ten days after the first spring heat commenced ; 

 in a fortnight after the opening heat-wave of the 

 summer they were a perfect pest; but as soon as 

 the summer temperature settled down to a daily 

 102 Fahr. or more, the flies began to diminish in 

 numbers again, until in August there were compara- 

 tively few it was too hot for the larvae. Then again 

 as the summer waned, the flies began to increase once 

 more, for the larvas were no longer killed by the 

 excessive heat. At a temperature of 54 Fahr., 

 Newstead found that the maggots were still in 

 the larval stages at the end of eight days. In the 

 winter the fly-larva hibernates its development is 

 delayed, for the low temperature causes a state of 

 suspended animation and the metamorphosis almost 

 ceases to progress until the weather becomes warmer. 1 



1 In India, Colonel Jennings, I. M.S., found that fly-larvae will hibernate 

 in burrows under the ground. In soft soil they can be found at a distance 

 of one foot from the surface. 



