9 
Two Common Orchard Mites. 
the soluble oil sprays were used in the experiments. 
It has been determined that lime and sulphur, applied when 
trees are dormant, will kill mites. Prof. Gillette has experimented 
with the lime and sulphur sprays upon the eggs of brown mite and 
has concluded that they are of no value as far as the destruction of 
the eggs is concerned. Their efficiency seems to depend upon their 
power to kill the young mites after they hatch from the eggs. Lime 
and sulphur is very adhesive, and the sulphides of lime will remain 
on a tree for months after the spraying has been done. Especially 
is this true in Colorado, where the rainfall is not great. 
SUMMARY. 
1. The brown mite has been quite a serious pest in Colorado the past 
season, doing considerable injury to orchard trees, as well as interfering 
with the maturity of the fruit. 
2. The over-winter eggs are deposited in late summer, most of them 
before the first of August this season; they remain on the trees throughout 
the winter and hatch shortly after the leaves come out in the spring. 
3. Apple, peach, plum, cherry, pear, and almond trees were found 
infested. Apricot and quince do not seem to be troubled. 
4. Mites feed principally upon the foliage where their presence may 
be detected by the pallid leaves, and the tiny black sipots of excreta. 
5. Flowers of sulphur, one pound to three gallons of water, and 
enough soap so that the sulphur will mix with water, is a perfectly effec¬ 
tive remedy when used as a summer spray. 
6. Tobacco preparations will kill the mites, but not the eggs, and are 
only effective when repeated applications are made. Oil sprays seem to 
penetrate the eggs, and destroy them better than the tobacco extracts, but 
are unsafe to use with water strongly impregnated with alkali. 
7. Trees may be treated while dormant with lime and sulphur. This 
spray has no effect upon the eggs, but probably kills the young mites as 
they hatch. 
The red spider (Tetrcmychus bimaculatus Harvey) Plate I, Eig. 2. 
Although there are a number of different species of red spiders, 
or spinning mites, we have found only one species infesting orchard 
trees in Western Colorado. While in most localities it was probab¬ 
ly not responsible for as much damage as the brown mite, still it 
was of somewhat serious consequence, and is a pest to be watched, 
and combatted if necessary, to keep it from becoming injurious the 
coming season. 
Life History 
Both species of mites treated in this bulletin belong to 
the same family, but differ from each other in many impor¬ 
tant respects. The eggs of the red spider are deposited chiefly 
on the under surface of leaves. An examination of infested trees 
will reveal the presence of these tiny transparent eggs, resembling 
minute dew-drops attached to the surface of a leaf, or interwoven 
among the silvery threads which the mites are capable of spinning. 
As is the case with the brown mite, these have only six legs when 
first hatched, the fourth pair developing later. The adult (Fig. 2) 
is somewhat smaller than the adult brown mite and the fore pair 
