1912] Incubation of Eggs of Samia Cecropia 69 



the 8th of this month in addition to the above mentioned nymph, 

 the last adult insect was seen. 



The eggs are green or yellowish-green in color, measuring about 

 0.7-0.8 mm. in length, 0.2 mm. in width, slightly curved in 

 shape, and almost equally pointed on both ends. Fig. a. 



As I could not find any of the females in the act of oviposit- 

 ing although I examined all the plant parts where females were 

 seen resting, and then after having kept the females so long in 

 captivity without any egg being deposited, I doubt whether the 

 insects lay their eggs in the food plant. They may do as I have 

 observed in the case of Campylenchia curvata which feeds on Soli- 

 dago and is found depositing its eggs on Vernomia. 



THE PERIOD OF INCUBATION OF THE EGGS OF 

 SAMIA CECROPIA. 



During the spring of 1911 it was found convenient to gather 

 data on the relation of each day's deposit of Cecropia eggs to their 

 period of incubation. 



The table on p. 70 shows the number of days required for the 

 hatching of the eggs of each of 36 females for the 1st, 2d, 3d, 4th, 

 5th, 6th, and 7tli day's deposit. Queries indicate that the eggs 

 did not hatch at all. 



The periods recorded are counted from the days when the great 

 majority of each day's lot hatched. In some instances a small 

 part of the caterpillars emerged a day earlier, and in a few other 

 cases a few stragglers were observed later. 



The table clearly shows that the period of incubation of the 

 eggs deposited between May 16 and June 26 varied from 6 to 11 

 days, the great majority being 8 or 9 days. The table also shows 

 that the period of incubation is practically the same for each day's 

 deposit; first or last oviposition does not seem to cause the period 

 of incubation perceptibly to vary. 



We see a few periods of 10 days and one of 11 days occurring 

 during the early experiments, but possibly climatic conditions at 

 that season can account for this prolonged time. 



St. Louis, Mo., February 14. Phil Rau. 



