374 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



error. Accurate experiments are necessary to establish the precise 

 temperature at which the eggs are killed. 



In the previous article 1 mentLoned that a very few young insects 

 hatched out at Ames in the spring of 1912. However, this was observed 

 on a single tree, and on only one branch of that tree, a branch close to 

 the ground on the southeast portion of the tree. Most probably this 

 limb had been protected by snow during the extreme weather, so that 

 it was not subjected to quite so severe cold as the rest of the tree. On 

 the rest of this tree, and on other trees in the orchard, the eggs were all 

 killed. 



The fact that empty scales remain on infested trees for several years 

 after the insect has died, and the eggs beneath have hatched out, is 

 misleading uo most people. A branch of wood may be literally in- 

 crusted with scales, yet an actual examination of these show that very 

 few or none of them contain anything alive. Such was the case in the 

 fall of 19l2, when only rarely were scales found that contained any- 

 thing alive beneath them. 



Figure 16 — Condition of oyster-shell scale in January, 1915. 



Condition in Winter of 1914-1915 



Only 3 samples of the scale were received in response to the request 

 of December, 1914. More replies than this were received, but no 

 samples of scale were sent. For instance, in 9 cases the parties ad- 

 dressed could not find samples to send in, though previously they had 



