26 Psyche [February 



suggested as the retarding factor since the eggs were in a rather 

 dry place compared with that in which they are usually laid and 

 it has been found that eggs in the laboratory must be kept in a 

 moist atmosphere to insure the emergence of the larvae. 



Of the thirty -five batches placed in direct sunlight none hatched, 

 but eighteen developed up to the hatching point. Twelve batches 

 showed no signs of hatching at the end of the eighth day. Five 

 of the batches were either blown away or destroyed by some ani- 

 mal. The only animals that could possibly be responsible for 

 the disappearance of these eggs were birds or large insects, but 

 whether or not they were responsible was not determined. 



Experiment II. 



On June 15, a beetle just about ready to deposit eggs was placed 

 on a plant in the garden and enclosed by a glass jar. Within two 

 hours she laid a batch of thirty eggs. Part of these were taken to 

 the laboratory where they hatched in six days (June 2'-2). The 

 leaf to which the rest of the eggs were fastened was bent over and 

 held in place so that the rays of sunlight would strike the eggs. 



At the end of twenty-four hours four of the control eggs and 

 four of those left on the plant were fixed. Sections of these eggs 

 show that development proceeded in both groups at the same 

 rate and that sunlight had no visible influence upon the devel- 

 opment of the eggs subjected to it. Another group of four were 

 taken from the plant at the same time and kept in the laboratory 

 in a moist watch glass. These hatched in the normal period (six 

 days) . Sunlight acting upon the fresh eggs for a period of one day 

 had therefore no effect upon the development of these embryos. 



The eggs on the plant in the sunlight should have hatched on 

 June 22. On this date the larvae within them could plainly be 

 seen; they failed to emerge within the next two days when the 

 experiment was concluded. 



General Conclusions. These experiments prove that the eggs 

 of the potato beetle in various stages of development are pre- 

 vented from hatching when kept in direct sunlight, but are not 

 retarded in their development. The non-hatching of these eggs 

 is probably due to partial dessication. The advantage of conceal- 

 ment is not so great therefore as that secured by shielding the eggs 

 from the dessicating properties of sunlight, since the potato beetle 



