58 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



in alcohol, it will be found advantageous to add 10 or 15% of glycer- 

 ine to the liquid some hours previously. This will retard evaporation 

 of the preserving fluid from the larva and allow time enough to make 

 a negative before the larva shrinks, which it will do rather too promptly, 

 unless this precaution is taken. 



Plates and Developer. In our experience it is nearly always desirable 

 and often essential to use a dry plate adapted especially to catch color 

 values: the kind of plate usually termed ortho- or isochromatic. 

 Many insects have shades of yellows or reds that the ordinary plate 

 will not catch at all, or at least but faintly: for example, the potato 

 beetle, or the twelve-spotted cucumber beetle. With ordinary plates 

 the spots in the latter will appear very dim, while with isochromatic 

 plates they will assume their proper brightness and differentiation, 

 although the lighting and all other conditions remain the same. 

 Color screens we have not used, since the ortho plates have seemed 

 to meet our needs in each case, with our method of lighting. They 

 may be highly desirable. The plates that we have used include the 

 Standard Orthonon, the Seed's Non-Halation Ortho, and the Cramer 

 Isochromatic. Our preference inclines somewhat toward the last. 

 Using this plate in medium speed emulsion, photographing at some 

 size, with the Zeiss Protar 11 3-16 inch lens, stopped down to 64, and 

 using our regular Nernst light with reinforcing rays from a concave 

 mirror, the length of exposure is one to one and one-half minutes for 

 an object of ordinary color value. The right exposure for the other 

 magnifications may readily be estimated from this. 



Preparation for Printing. Most negatives showing an object on a 

 white background will make better prints if the background is ''painted 

 out." By this is meant covering the background as it appears in the 

 negative with one of the prepared "opaques," sold for this purpose, 

 leaving only the image of the object itself unpainted. The material 

 is thinned somewhat with water and is applied with a fine brush directly 

 to the film side of the dried negative. The finest and smallest size 

 brush will be needed for working up close to the image, while a larger 

 brush may be used for blocking in the remainder. A convenient 

 retouching stand can be made by fastening a piece of glass about 12 x 

 16 inches square in a simple frame, and supporting this at a moderate 

 incline, so that light will be admitted from beneath. A reading glass 

 is of much assistance in tracing the outline of the object. A print 

 from a negative that has been thus painted out will invariably be 

 better and cleaner cut, even though the original background appeared 

 fairly dense in the negative. Where extraneous objects show in the 

 negative this process of elimination is doubly valuable. 



Prints for Half-Tones. Most prints today that are not intended 



