58 Belladonna Leaf-Miner 



Chittenden (p. 51), quoting Howard, gives it as three to four days in 

 the case of the synonym P. mcina. The time will vary according to 

 the weather conditions and temperature, and to the degree of exposure 

 of the eggs on the various leaves. In the laboratory where a tem- 

 perature of 70° F. was maintained, the eggs hatched usually after the 

 short interval of three days. 



In order to get an ajDproximately accurate idea of the duration of 

 the egg period, the belladonna host plant was kept under close obser- 

 vation in the open. As soon as a leaf was noted with eggs newly deposited, 

 a tag-label bearing the date was attached to the stem immediately 

 below the leaf petiole and numbered. From time to time the leaves 

 thus marked were closely examined. A fairly exact idea was thus 

 obtained of the time occupied in the development of the embrvo within 

 the egg. Some of the results are appended in Table I : 



Table I. Pegomyia hyoscyami and its oviposition. 



Number of Date of Number of Eggs Date of Hatching Number of 

 Experiment Oviposition in a Group of First Egg Days 



It must be observed that the larvae generally hatched in the cool of 

 the evening, and in a few cases the emergence of the larva occurred 

 during the night. In these latter the time could only be guessed at, but 

 with quite a close approximation to the truth since an indication would 

 generally be got of the time that the larva had abandoned the egg, from 

 the progress which it had made with its gallery beneath the epiderm. 

 The eggs of any one group do not hatch synchronously, but the variation 

 in time is often only one of minutes. As long as twenty-four hours 

 between the hatching of the first and last eggs have been noted. Later 

 in the season, towards the end of September, a single case where the 

 eggs took eight days to hatch was recorded. 



The number of eggs which any one individual will deposit cannot 



