392 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
A point of importance in practical fumigation is the amount of injury 
which may be expected if the liquid bisulphide touches the seeds. It is 
commonly assumed that the injury will be much greater in this case. A 
few experiments conducted to test this are reported in Table 7. 
Apparently there is no likelihood of injuring corn by any commercially 
practical treatment with bisulphide, since it withstood 30 days immersion 
in bisulphide with a loss in germination of only twelve per cent. Even 
then the seedcoat was punctured directly over the scutellum of the germ, 
88 per cent of those immersed in bisulphide for twenty-four hours 
germinated. The other seeds showed much greater injury from immer¬ 
sion in the liquid than from treatment with the gas, but the injury was 
not sufficient to suggest any practical danger from pouring bisulphide 
directly on seeds for fumigation. In practice, we have done this for 
years without injury. 
ON THE OYSTER-SHELL SCALE FOUND ON WILLOWS AT 
BOULDER, COLORADO 1 
By R. L. Shotwell, Boulder , Colo. 
A heavy infestation of the Oyster Shell Scale (Lepidosaphes ulmi) 
has recently been discovered on willows in a small half-acre clump in 
Gregory Canon, Boulder, Colorado. The altitude of this particular 
spot is about 5600 feet. This insect has also been reported from other 
parts of the state, Fort Collins and Denver. That the insect was brought 
from Denver to this place on the feet of birds is the opinion of Dr. 
T. D. A. Cockerell. 
The following trees and shrubs are found in the vicinity of the infested 
willows: two species of Populus (broad-leaf and narrow-leaf cotton¬ 
woods) , Pinus (western yellow pine), Alnus (alders), Crataegus (thorn- 
apple), Prunus (wild plum), Acer (Rocky Mountain maple and box 
elder), and rosebushes. All of these are in close proximity to the wil¬ 
lows, but do not have any of the insects on them. One small rosebush 
had a few scattered scales on it, but they were poorly developed. Prof. 
C. P. Gillette of Ft. Collins writes: “The lilac and ash trees in a city 
park in Ft. Collins are being killed by this scale, while a number of 
flowering crabs growing under these trees do not have any of the scales 
upon them. In fact we do not find Lepidosaphes ulmi on any of the 
apple trees here.” 
The following table shows the difference in the average number of 
Contribution from the Entomological Laboratory, University of Colorado. 
