SOME TREE-DESTROYING INSECTS. 
7 
tree by inserting the beak beneath the surface and sucking out the 
sap. Among these may be mentioned the different forms of 
scale insects, such as the cottony maple scale and oyster-shell 
bark louse. This group also includes the leaf hoppers, tree 
hoppers, and plant lice. The scale insects are usually rather hard 
to combat on account of the scaly covering or armor which protects 
the insects from any spray that one may use against them. To kill 
such forms during the growing season, the spray would have to be 
strong enough to injure the foliage, hence, during this time, all one 
can do is to keep the young insects from wandering over the tree 
too promiscuously. For instance, the eggs of the oyster-shell bark 
louse pass the winter under the old scale of the mother insect. 
These eggs hatch in the spring, and for a few hours, the young 
wander around before settling down on the bark. At this time, if a 
spray of weak lime sulphur or kerosene emulsion or some good con- 
tact insecticide is used, thousands of these small forms will be 
killed. The same sprays will prove effective when applied to the 
cottony maple scale which hibernates on the small twigs and 
branches. ' If a thorough spraying is given with the dormant lime 
sulphur early in the spring ninety per cent probably or more of 
these insects will be killed. When the leaves are off the tree, the 
spraying can be much more thoroughly done. 
In the case of the leaf hoppers and the plant lice, we again have 
to resort to a contact insecticide. These insects must be touched to 
kill them and we find, particularly for the plant lice or “greenfly” 
that there are several sprays that will readily control them. Among 
'these may be mentioned tobacco extracts, such as black Leaf No. 
40, nicofume and nicoticide. Whale oil soap added to this at the 
rate of one pound to ten gallons will make the solution still more 
valuable. 
Of the forms that bore under the bark and within the wood, 
the following are the most important found in Minnesota : the two- 
lined chestnut borer, the bronze birch-borer, and the elm-borer. 
To this class belong those insects which give the most trouble to 
the owners of trees. The work is all done out of sight, beneath the 
bark, and almost the first notice one has of any injury is the dying 
of the trees. 
The adults of all these forms are beetles. They fly, commonly, 
during the months of May and Tune, even in July in the case of 
