54 



cold-storage vaults for these and other experiments. The following 

 temperatures were tried on two lots of eggs, some freshly laid and 

 others partly developed. After the periods mentioned the respective 

 lots of eggs were removed and the percentages hatching noted, as 

 shown in the table: 



Table XVI. — Effect of lower temperatures on eggs. 



Treatment. 



First series— eggs with trace 

 of brown ring. 



Second series— brown ring 

 well formed. 



34° F. for 48 hours 



34° F. for 24 hours, then 27° F. for 72 hours. 

 34° F. for 24 hours, then 27° F. for 24 hours, 

 then 18° F. for 72 hours. 



About 90 per cent hatched . . 

 About 50 per cent hatched. . 

 About 25 per cent hatched. . 



Practically all hatched. 



Do. 

 About 33 per cent hatched. 



It is evident from the figures in the table that eggs which are 

 further developed are less susceptible to the effects of cold, and that 

 the eggs are able to withstand short periods of cold better than longer 

 ones. Although there was only about twelve to eighteen hours differ- 

 ence in the age of the eggs in the two series, the proportion hatching 

 from the older one was from 10 to 50 per cent greater. Some of the 

 larvae hatching from these eggs were kept to see if they had been 

 weakened in any way by the cold, but all seemed as healthy as larvae 

 hatched under normal conditions. The shock to the ^gg in the experi- 

 ments must have greatly exceeded that caused by any sudden cold 

 spell to which they might be subjected in the early spring. 



EFFECT OF ATMOSPHERIC CONDITIONS. 



Moisture and dryness seem to have no effect on the time required 

 for development. A number of eggs submerged under water shortly 

 after they were laid and others placed in a desiccator dried by sul- 

 phuric acid, hatched in practically the same length of time as a check 

 lot under normal conditions. This resistance to atmospheric conditions 

 is no doubt due to the thick, impervious, chitinous eggshell which 

 prevents the transpiration of water vapor to any extent. 



EFFECT OF SUBMERGENCE ON EGGS. 



In the spring a good proportion of the eggs are deposited on young 

 corn plants; they are often subjected to wetting by heavy rains which 

 occur during this season of the year, and at times are washed down 

 into the "bud" where the rain water accumulates. To ascertain how 

 much submergence under water the eggs are able to withstand, a 

 number of experiments were tried in the laboratory. On June 4, 84 

 freshly laid eggs were submerged in six lots for periods varying from 

 twenty-five minutes to four hours. Of these only 2 failed to hatch, 

 and these were not in the lot which was under water longest. At 

 another time a card with -35 eggs attached was placed in a vial of 



