Ete 
For convenience in handling, four slides are placed in an aluminum 
clip which has the ends turned back over the slides so that the glass 
surfaces willnot touch when several clips are stacked (fig. 3). Two 
upturned stops on the back margin of the clip prevent the slides from 
falling out. While held in the clip, the upper surfaces of the four slides 
are coated by brushing with a hot mixture of mineral oil and vaseline. 
The proportion of the two ingredients depends upon field temperatures. 
The mixture should be fluid enough to spread uniformly in a thin film 
over the slide without showing brush marks, but firm enough not to 
flow under high temperatures. Brush marks greatly hinder the counting, 
as only those mites directly above white areas showing through the glass 
Slides are counted, and the uneven refraction of light through irregular 
adhesive surfaces obscures the outline of these areas. Three parts of 
mineral oil to one of vaseline is satisfactory; the proportion of vaseline 
is increased with higher temperatures and decreased with lower ones. 
The mixture may be applied cold, but it is more difficult to avoid leaving 
brush marks when applying a thin film. 
After the slides have been coated, they are stacked in one side of a 
metal slide box (fig. 4). This box has two compartments--one for 
carrying the clean, coated slides to the field and the other for holding 
the slides after the mites have been collected. Three of these slide 
boxes are placed in a metal case for carrying to the field (fig. 5). A 
large number of the slides may be coated and held indefinitely in these 
carrying cases for future sampling. 
In the field to be sampled a slide box is removed from the carrying 
case and taken to the sampling site. A clip of slides is taken from 
the box and rested on the flat surface of the fork. The slides are then 
removed individually from the clip and inserted in the tines of the fork 
with the adhesive surface on top, being held in position by the retaining 
rim (fig. 6). The sampling fork is then ready for use. 
Using the Fork 
The fork containing the coated slides is inserted through the base 
of the plant at ground level (fig. 7), and the foliage is disturbed by 
brushing with the hand so that the mites will drop to the ground; those 
that fall on the slides are held by the adhesive. The fork is then with- 
drawn and the slides are replaced in the clip. The bottom or outside 
top margin of the clip is labeled with a lead pencil as to sampling site, 
date, host, or other desired data. The clip of slides is then returned 
to the holding box, and when all the collections have been made the box 
is placed in the carrying case and brought back to the laboratory for 
counting. The samples may be held in good condition for many days 
in the refrigerator. 
